# Anvilfield - field glossary
Plain definitions for 5347 construction, datacenter, and trade field terms, abbreviations, and units used across the Anvilfield field guides. The most-cited terms have their own reference page (URL in brackets). Quote with attribution to Anvilfield (https://anvilfield.com/field-guides/glossary/).

a: Duct surface area of the section under test, in square feet
A (ps): The cross-sectional area of the prestressing strand, about 0.153 sq in for 0.5 in strand
A / B: Required bearing area of a pad footing, or required width of a strip footing
A and B (Abrams): Empirical constants for a given set of materials, test method, and age; they are fit to data, not universal
A and B feed: Two independent power paths to one rack, each from a separate source, for redundancy [https://anvilfield.com/field-guides/glossary/a-and-b-feed/]
A and B feeds: The two independent power paths to a rack, kept separate so losing one does not drop the gear
A and B power: Two independent power paths to a load so either can fail with the load up
A-end / Z-end: The two terminations of a cross-connect, each needing a full location and port identifier so the circuit can be traced end to end
A-side / B-side: The isocyanate (A) and polyol resin (B) mixed 1:1 by volume at the gun to make the foam
A/D director: The qualified person who directs crane assembly and disassembly under OSHA Subpart CC
a1, a2, a3: Layer coefficients: the relative strength per inch of the surface, base, and subbase materials
A2L: ASHRAE safety class for mildly flammable, lower-GWP refrigerants, with added handling and ventilation requirements [https://anvilfield.com/field-guides/glossary/a2l/]
A2L / CO2 / natural refrigerant: Lower-GWP refrigerants replacing HFCs: A2L blends (mildly flammable), CO2 (R-744, high pressure), and naturals like propane (R-290, flammable) and ammonia (R-717, toxic)
A325 / A490: The 120 ksi and 150 ksi structural bolt grades, now grades within F3125
A90C: Base ampacity from NEC Table 310.16, read in the 90 degree C column for 90 degree C insulation
A_c: Cross-sectional area of one insulated conductor, from NEC Chapter 9, Table 5, for the size and insulation actually installed
A_cables: Sum of the cross-sectional areas of every cable in the tray section, in square inches
A_conduit: Total interior cross-sectional area of the conduit, from NEC Chapter 9, Table 4, by type and trade size
A_total: Sum of all conductor areas in the raceway, including the neutral and the equipment grounding conductor
A_usable: Inside width times usable depth of the tray, with depth capped at 6 in for the NEC fill rules
AA-8000 series: The modern aluminum building-wire alloy the NEC requires for most aluminum conductors, reformulated to hold a termination
AASHTO M288: The geosynthetic specification setting geotextile properties by application and survivability Class 1, 2, or 3.
AAV: Air admittance valve, a one-way valve that admits air on negative pressure and seals against sewer gas; often called a Studor vent after the original brand [https://anvilfield.com/field-guides/glossary/aav/]
Ab: Required block bearing area against undisturbed soil, in square feet
Abandon in place: Disconnect at both ends, de-energize, verify dead, and leave the dead wire where it is
Abandoned cable: Cable not terminated and not tagged for future use; the accessible portion must be removed under the NEC
ABC: Automatic baseline correction, an algorithm that recalibrates a CO2 sensor by assuming its periodic low reading equals fresh outdoor air
ABC / positive sequence: The standard sequence; ABC, BCA, and CAB are all the same order
ABC analysis: Sorting parts by movement: A items move constantly, B moderately, C rarely
Abiotic stress: Damage from non-living causes such as compaction, deep planting, drought, excess water, salt, or mechanical injury, the source of most decline
Abrasive media (non-silica): Garnet, slag, or steel grit/shot used to blast, in place of silica sand, which causes silicosis
Absolute / specific humidity: Actual mass of water per mass of dry air, independent of temperature
Absolute pressure: Pressure measured up from a perfect vacuum, not from atmosphere; how a deep vacuum is read
Absorption current: The slowly decaying polarization current that makes a healthy reading climb over time
Absorption distance: The duct length a steam plume needs to fully evaporate before reaching a surface or sensor
AC / asphalt binder: The liquid asphalt cement that coats the aggregate, graded by PG grade
ACB / CBA / negative sequence: The reverse sequence; ACB, CBA, and BAC are all the same reversed order
Acceptance criteria: The standard or value a test result is measured against to pass, from the project spec, the discipline standard, or the manufacturer [https://anvilfield.com/field-guides/glossary/acceptance-criteria/]
Acceptance factor: The fraction of tank volume usable for expansion, set by the ratio of fill to maximum pressure (Boyle's law)
Acceptance volume: The amount of expanded water the tank can actually take in before pressure rises to the limit, always less than the shell size [https://anvilfield.com/field-guides/glossary/acceptance-volume/]
Access aisle: The marked lane beside an accessible space, part of the space, where a lift deploys; 5 ft or 8 ft wide
Access control: Knowing and managing who is on the site through a controlled entrance, a sign-in, and a short, named after-hours key list [https://anvilfield.com/field-guides/glossary/access-control/]
Access floor / raised floor: The raised panel floor on adjustable pedestals over the structural slab, creating an underfloor plenum or service space [https://anvilfield.com/field-guides/glossary/access-floor-raised-floor/]
Accessible route: A continuous path from the access aisle to the entrance, no steps, max 5 percent running slope
Acclimation: Letting the wood reach equilibrium moisture content with the conditioned space before install, with the HVAC running
Acclimatization: The body's adaptation to heat over roughly 1 to 2 weeks of gradual exposure; lost after time away from the heat
Accountable plan: An IRS-recognized reimbursement structure under which per diem and expenses stay non-taxable when properly substantiated
Accounts payable (AP): The money you owe suppliers for material and services bought on account, not yet paid
Accounts receivable (AR): Money customers owe you for work already completed and billed
Accrual: Recognizing an expected cost in the period the related revenue is earned rather than when the cash goes out, which is the matching idea behind a warranty reserve. How it is booked is the CPA's call.
Accumulator: Suction-line reservoir that protects the compressor from liquid floodback in heating and defrost
Acetylene 15 psi limit: The maximum working pressure for acetylene, which becomes unstable when compressed higher
ACH: Air changes per hour, supplied air volume divided by room volume each hour
ACI 318: The structural concrete code, for strength acceptance and the anchoring-to-concrete provisions in its Chapter 17
ACI 318 / ACI 117: The structural concrete code for placement requirements, and the tolerance specification for cover and d
Acid stain (reactive stain): Metallic salts in a mild acid that react with the lime in the concrete to deposit permanent, variegated, earth-tone color
Acidic condensate: The weak acid a condensing appliance makes when flue-gas water vapor condenses, commonly pH 3 to 4 on gas
ACR / ASCS: ACR is the NADCA standard; ASCS is the Air Systems Cleaning Specialist, the NADCA individual certification
ACR copper: Air-conditioning-and-refrigeration tube, cleaned, dehydrated, and capped, sized by actual outside diameter
ACRF (ELFEXT): Far-end crosstalk normalized to insertion loss; the older name was ELFEXT
Action item: A single specific task with one accountable owner and a firm due date, tracked to closure
Action level: The exposure near 85 dBA over 8 hours that triggers the hearing conservation program
Action threshold: The pest count or damage level that justifies treating; below it, you monitor and do not treat
Activated sludge / biological treatment: The suspended-growth secondary process where microorganisms in aerated mixed liquor eat the organic waste, then settle out
Activation energy: The Arrhenius parameter for temperature sensitivity, often 40,000 to 45,000 J/mol
Active chilled beam: A beam fed with ducted primary air whose nozzles induce room air across the coil, delivering ventilation and added sensible cooling
Active RDHx: A rear door with its own fans that draw exhaust through the coil, taking the back pressure off the server fans
Active vs dormant crack: Active cracks are still moving; dormant cracks have stabilized, which decides the repair
Active vs passive DAS: Active converts RF to fiber and re-amplifies at remote units for large buildings; passive is a BDA feeding coax and antennas for smaller ones
Active vs passive wheel: Active has a regeneration heater and dries to a target; passive (enthalpy) only recovers energy
Actuator: Electric or pneumatic motor, usually spring-return, that closes a smoke or combination damper on signal
ACV vs RCV: Actual cash value is replacement cost minus depreciation; replacement cost value is the full cost to replace the roof today
ADA accessible space: A space meeting the 2010 ADA Standards: 8 ft wide with a 5 ft access aisle, max 2 percent slope
ADA graspability / extensions: A 1 1/4 to 2 in graspable handrail with extensions past the top and bottom nosings and returns to wall or floor
Addendum: A change to the bid or procurement documents issued before the contract is executed [https://anvilfield.com/field-guides/glossary/addendum/]
Additional charge: Refrigerant added beyond the factory charge, calculated from liquid-line length and diameter and weighed in
Additional insured: An endorsement naming another party on your policy so your coverage defends them for your work
Adhesion test: A small coated patch or fabric pull tab cured and pulled to confirm the coating bonds to the substrate before the field coat
Adhesive / chemical anchor: A rod or rebar bonded into a drilled hole with structural adhesive; strength is the bond, not expansion
Adhesive / cohesive failure: Sealant peeling off a wall versus splitting through its own body
Adiabatic / evaporative cooling: Using water evaporation to drop air or surface temperature and extend the free-cooling hours
Adiabatic humidification: Evaporating water using the air's own heat, which cools the air as it humidifies
Adjustment factor: The more-than-three-conductor multiplier from 310.15(C)(1)
Administration: The TIA-606 discipline of identifying, labeling, and recording the cabling infrastructure so any component can be named and any link traced
Admixture: Anything besides cement, water, and aggregate added to the mix to change a property
ADPI: Air diffusion performance index, a 0 to 100 measure of how uniform and comfortable the occupied zone is
Adsorption: Water vapor adhering to the surface of the desiccant, driven by a vapor-pressure difference
AED: Automated external defibrillator, which reads the heart rhythm and delivers a shock only if one is needed
AEGCP: Assured equipment grounding conductor program, the written OSHA program that tests and records the ground path on temporary power equipment [https://anvilfield.com/field-guides/glossary/aegcp/]
Aeration / dissolved oxygen (DO): Blowers and diffusers supply oxygen to the bugs; DO in mg/L is the measured oxygen in the tank, commonly held above about 2 mg/L
Aerator: The screen at the tip of a faucet that mixes air into the stream and catches scale and debris; the number-one single-fixture restriction
AFCI: Arc-fault circuit interrupter, protects the building by detecting the signature of an arcing fault
Affected employee: A worker who operates or works near the equipment but does not perform the servicing, and who must be notified
Affinity laws: Flow scales with speed or impeller diameter, head with the square, and power with the cube of the change [https://anvilfield.com/field-guides/glossary/affinity-laws/]
AFUE: Annual fuel utilization efficiency, a seasonal efficiency percentage from a standardized test [https://anvilfield.com/field-guides/glossary/afue/]
Aged binder: The oxidized, stiffened asphalt binder on RAP, harder and more brittle than fresh binder
Agenda: The list of items and the purpose for a meeting, distributed ahead so people arrive ready
Aggregate base: The compacted crushed-stone layer under the asphalt that carries the load; also road base or DGA [https://anvilfield.com/field-guides/glossary/aggregate-base/]
Aggregate broadcast: Silica sand seeded into a wet coat for slip resistance and to take the wear of traffic
Aggregate exposure (CPC class A/B/C): How much stone the grind reveals, from cream paste (A) to salt and pepper (B) to full aggregate (C)
Aggregate interlock: Load transfer through the rough crack faces below a tight sawcut joint
Aggregate type (I, II, III): ISSA gradation classes from fine to coarse that set the application rate and the duty the course can carry
Agreement density: The share of total revenue under contract, a driver of company valuation
AHJ: Authority having jurisdiction, the official who adopts the editions, witnesses or reviews the test, and settles conflicts [https://anvilfield.com/field-guides/glossary/ahj/]
AHJ / CASp: Authority having jurisdiction; Certified Access Specialist, a state-recognized accessibility inspector
AHJ / water authority: The local authority whose standard spec and details govern the main
AHRI: The body that certifies the matched indoor and outdoor combination and its rating
AHU: Air handling unit, the indoor central air handler that conditions and moves air through duct
AI / AO / BI / BO: Analog input, analog output, binary input, binary output, the four I/O point types [https://anvilfield.com/field-guides/glossary/ai-ao-bi-bo/]
AI video analytics: Software that detects objects and conditions in the video, such as missing PPE, intrusion, or a zone breach
AIA G701: The common executed change order form that adjusts the contract sum and contract time
AIC: Ampere interrupting capacity: the maximum fault current an overcurrent device can interrupt, a device-level rating [https://anvilfield.com/field-guides/glossary/aic/]
AIC / interrupting rating: The largest fault a single overcurrent device can interrupt safely, in amps or kA
AII vs PE: Airborne infection isolation (negative, contains the patient's pathogens) versus protective environment (positive, protects the immunocompromised patient)
AIM Act: American Innovation and Manufacturing Act of 2020, which sets the HFC phasedown
Air balance: Supply outdoor air plus infiltration set against exhaust plus relief plus exfiltration
Air barrier: A layer or system that stops air leakage through the envelope, rated by air permeance and required to be continuous and sealed [https://anvilfield.com/field-guides/glossary/air-barrier/]
Air binding: Air carried into or trapped in the pump; noisy and performance-robbing, but it does not implode and erode like cavitation
Air break: A waste pipe ending below the flood rim but above the trap seal, allowed for lower-hazard clear-water discharges
Air chamber: The old capped pipe stub fix that waterlogs as its air dissolves into the water and then fails
Air change rate: The room volume exchanged per hour, the measure of how fast the air is diluted and swept
Air change rate (ACH): How many times per hour the room's full air volume is replaced, the dilution rate the table sets by space
Air clearance (PCM / TEM): Post-work air sampling against a clearance level, PCM around 0.01 f/cc or TEM specific to asbestos, signed by an independent party
Air content: Total air as a percent of concrete volume, the field-tested number judged against the specified target
Air curtain / air door: A unit over an opening that blows a high-velocity stream across it to separate inside from outside
Air entrainment: Deliberate creation of tiny, stable, evenly spaced air bubbles in concrete using an admixture, for freeze-thaw and deicer durability [https://anvilfield.com/field-guides/glossary/air-entrainment/]
Air gap: Open vertical space between the waste pipe outlet and the receptor flood rim, commonly 2x the pipe diameter with about a 1 in minimum [https://anvilfield.com/field-guides/glossary/air-gap/]
Air maintenance device: Regulator and restriction that tops off supervisory air or nitrogen slowly, so a real operation drops pressure faster than it refills
Air mixer: A venturi that adds combustion air to propane for a clean burn; not needed for natural gas
Air mover: High-velocity fan that evaporates moisture from wet surfaces into the air for the dehumidifier to remove
Air mover vs dehumidifier: An air mover evaporates moisture off surfaces; a dehumidifier removes that moisture from the air
Air permeance: Air leakage per unit area at a test pressure, in cfm per square foot at 0.3 in. w.c., measured by ASTM E2178 and E2357
Air separator: A loop fitting that strips entrained air from the water, placed at the hot, low-pressure point off the boiler supply
Air terminal: The rod or point that intercepts the strike, also called a lightning rod or strike termination device
Air vent: A manual or automatic valve at each system high point that lets collected air out so the pump does not have to move it
Air voids: The percentage of air in the compacted mat; high voids let in air and water and shorten pavement life [https://anvilfield.com/field-guides/glossary/air-voids/]
Air vs water-cooled: Air-cooled rejects heat to room air and needs clearance; water-cooled rejects heat to condenser water and uses more water
Air-cooled vs water-cooled chiller: Heat rejected to outdoor air with a condenser coil, versus to a cooling tower through a condenser-water loop
Air-entraining admixture (AEA): The surfactant added at the plant that creates and stabilizes the entrained air, specified to ASTM C260
Air-free CO: Carbon monoxide corrected for excess air so readings compare against a target; calculated from measured CO and O2
Airflow management: Getting cold supply to every inlet and hot exhaust back to the units without the two streams mixing
Airside economizer: An economizer that brings filtered outdoor air into the hall or the air handler
AISC 360: The Specification for Structural Steel Buildings, the design and construction standard for structural steel
AL / AL-CU: Connector markings for conductors the lug is listed to terminate: aluminum only, or aluminum and copper
AL9CU / AL/CU: A connector marking meaning it is listed and tested for both aluminum and copper conductors
Alarm fatigue: The state where too many false or nuisance alarms train the operator to ignore, mute, or disable the detection system, which makes the technology worthless. Fixed by tuning the detection zones.
Alarm rationalization: Reviewing every potential alarm against an alarm philosophy so only meaningful, actionable, prioritized alarms remain, each with a documented consequence and response.
Albedo / solar reflectance: The fraction of sunlight a surface reflects; concrete is higher than dark asphalt
Alert / Action / Fire 1 / Fire 2: The rising alarm levels of a multi-stage aspirating detector, from earliest warning to the threshold that drives suppression
All-air / all-water / DX: The three distribution carriers: conditioned air in duct, hot or chilled water in pipe, or refrigerant in line sets
Allowable range: The wider band the equipment tolerates, set by class, intended for short excursions
Allowance: A placeholder dollar amount for a specific, identified item not yet priced, such as fixtures still to be selected, reconciled to actual cost later. [https://anvilfield.com/field-guides/glossary/allowance/]
Allowance vs contingency: Allowance covers a known unknown; contingency covers the unknown unknowns
AlumiConn: The CPSC-recognized set-screw connector that joins a copper pigtail to the aluminum in a tin-plated block
AM: Asymmetry multiplier, for twisting away from straight ahead
AMCA 220: The test standard for air curtain aerodynamic performance; a certified rating is the credible number
Amine blush: A greasy carbamate film on curing epoxy that acts as a bond-breaker between coats
Ammonia (NH3 / R-717): The efficient industrial refrigerant, toxic and flammable, regulated under PSM at a large charge.
Amp-hour (Ah): Battery capacity; more amp-hours means longer pump runtime at a given draw
Ampacity: The current a conductor carries continuously without exceeding its temperature rating, after correction and adjustment [https://anvilfield.com/field-guides/glossary/ampacity/]
Amps: Current the load pulls, found by dividing total watts by the supply voltage, commonly 120 V
Anchor: The high option presented first, against which the middle option reads as the reasonable choice [https://anvilfield.com/field-guides/glossary/anchor/]
Anchor and guide: A fixed point that holds the pipe still and the supports that let it slide lengthwise while staying in line, used to direct thermal movement
Anchor bolt setting plan: The manufacturer's drawing giving the location, pattern, projection, and diameter of every anchor bolt the frames land on
Anchor point: An engineered fixed tie-off rated to hold a fall, commonly 5,000 lb per worker or designed to a safety factor of two
Anchor profile: The peak-to-valley roughness the blast cuts into the steel, measured in mils, that the coating grips
Anchorage: What the system ties off to, rated at 5,000 lb per worker or engineered to a safety factor of two
Anemometer: Reads air velocity in feet per minute, vane or hot-wire, converted to CFM with the free area
Angle pull / U pull: Conductors change direction in the box, sized at 6x the largest raceway plus the others in the row
Angle stop: The shutoff valve on a fixture supply stub-out, trimmed with an escutcheon, that isolates the fixture for service
Angstrom: The length unit the coupon corrosion is measured in, one hundred-millionth of a centimeter
Annealed / tempered / laminated: Ordinary float glass that breaks in shards, heat-treated glass that breaks in pebbles, and bonded glass that holds together on an interlayer
Annex B / 310.60: The NEC duct-bank ampacity figures, Annex B for low voltage and 310.60 tables for 2001 V to 35000 V; verify against the adopted edition
Annex C: Lookup tables giving the maximum conductor count when all conductors are the same size and insulation
Annual: A plant that completes its life in one growing season and is replaced rather than overwintered, the basis of color rotation
Annular gap: The space between the damper sleeve and the rated opening, sized and filled per the listing
Annular space: The gap between the pipe and the edge of the opening, with a tested min and max [https://anvilfield.com/field-guides/glossary/annular-space/]
Annunciator: The panel, usually at the fire command center, that reports system trouble such as AC loss, low battery, and donor or antenna failure
Anode / rectifier: The anode is where corrosion is directed; the rectifier is the AC-to-DC power source that drives an ICCP system
Anode rod: Sacrificial magnesium, aluminum, or zinc-alloy rod that corrodes in place of the steel tank [https://anvilfield.com/field-guides/glossary/anode-rod/]
ANSI cut level (A1 to A9): ANSI/ISEA 105 rating of glove cut resistance, A1 lowest to A9 highest
ANSI device number: Two- or three-digit protective function code per IEEE C37.2
ANSI device numbers: The IEEE C37.2 identifiers for relay functions: 50 instantaneous overcurrent, 51 inverse-time overcurrent, 87 differential, 27 undervoltage, 59 overvoltage, with G or N for ground
ANSI/SPRI ES-1: The national test standard for low-slope roof edge systems, with the RE-1, RE-2, and RE-3 wind tests
ANSI/SPRI RP-4: The wind design standard for ballasted single-ply roofs, turning height, exposure, slope, and parapet into a ballast design
Anteroom: A small airlock between an isolation room and the corridor that holds an intermediate pressure for a staged cascade
Anti-graffiti film: A clear sacrificial layer that takes tags and scratches so the film is replaced, not the glass
Anti-icing: Treating dry pavement before a storm to stop snow and ice from bonding to the surface
Anti-islanding: Protection that disconnects on-site generation from a de-energized utility line, per IEEE 1547 and UL 1741
Anti-oxidant compound: Joint compound applied to aluminum connections to break and exclude the oxide film
Anti-passback: A rule that a credential must exit a zone before it can enter again
Anti-scald valve: An automatic compensating shower valve listed to ASSE 1016, pressure-balance, thermostatic, or combination, that holds outlet temperature when pressure shifts
Anti-strip: Hydrated lime or a liquid additive that restores the binder-aggregate bond against moisture
Antioxidant compound: Oxide-inhibiting joint compound applied to aluminum connections where required, to break and seal out the aluminum oxide film
Antiquing: The secondary accent color left in the grout lines and low texture, from the release or a separate tinted product
AOS (apparent opening size): The opening size that controls which soil particles pass, written O95; a smaller AOS retains finer soil.
APF: Assigned protection factor, the exposure reduction a respirator class is credited with; common concrete rows use APF 10, long tuckpointing APF 25 [https://anvilfield.com/field-guides/glossary/apf/]
API separator: Plain gravity oil/water separator using residence time to float free oil
APP: Atactic polypropylene, the plastic modifier; heat and UV tolerant, almost always torch-applied
Apparatus dew point: The effective coil surface temperature where the extended process line meets saturation
Application rate: The volume of diluted material sprayed per unit area, commonly gallons per square yard, set by the product and the surface [https://anvilfield.com/field-guides/glossary/application-rate/]
Apprentice ratio: The allowed number of apprentices to journeyworkers on prevailing-wage work, set by the registered program
Apprenticeship: A paid, earn-while-you-learn pathway combining on-the-job hours with classroom instruction, often running 18 to 48 months
Approach: The difference between condensing refrigerant temperature and leaving condenser-water temperature; a rising condenser approach points to fouling or non-condensables [https://anvilfield.com/field-guides/glossary/approach/]
Approach (tower): Leaving condenser water minus the ambient wet-bulb; the tower cannot make water colder than the wet-bulb
Approach temperature: The gap between facility water in and coolant out at the heat exchanger; a widening approach signals fouling [https://anvilfield.com/field-guides/glossary/approach-temperature/]
Approved as noted: A review stamp allowing the work to proceed with the reviewer's markups incorporated, without a resubmittal
Appurtenance: Anything mounted on the tower beyond the structure: antennas, RRUs, mounts, platforms, lines, lights, each adding load and wind area
APR: Annual percentage rate, the yearly cost of the loan including interest
Apron / headwall flashing: A continuous piece run over the roofing where the top of a slope meets a wall
APWA color code: The national color standard for utility marks, from red electric to white proposed excavation
Aquifer / static water level: The water-bearing formation, and the depth to water in the well with the pump off
AR aging: A report sorting unpaid invoices by age into current, 30, 60, 90, and 90-plus buckets
AR days (DSO): Average days to collect after billing; days sales outstanding
AR vs FR: Arc-rated is flame-resistant fabric that also carries a tested arc rating; all AR is FR, not all FR is AR [https://anvilfield.com/field-guides/glossary/ar-vs-fr/]
Arbor: A small lattice-sided accent over a walk or gate, not a structure people gather under
Arc energy: The formula result before the process efficiency factor, what AWS practice calls heat input
Arc rating (ATPV / EBT): The cal/cm2 protection value of arc-rated clothing, from the arc thermal performance value or energy of breakopen threshold [https://anvilfield.com/field-guides/glossary/arc-rating-atpv-ebt/]
Arc reflection: TDR plus a surge, so the TDR reads the momentary arc at a high-resistance fault
Arc-flash boundary: The distance from the gear where incident energy drops to 1.2 cal/cm2, the onset of a second-degree burn [https://anvilfield.com/field-guides/glossary/arc-flash-boundary/]
Architectural millwork: Custom non-box woodwork built for a project: trim, paneling, desks, casing, and one-off pieces, as opposed to the cabinet boxes
Arcing current: The current that actually flows in the arc, lower than the bolted fault current; a method must operate at less than this to work
Arcing ground fault: A line-to-ground arc drawing far less than the phase device trip level, which burns the gear
Area: Bed or lawn surface in square feet, length times width
Area classification study: The qualified engineer's documented analysis that sets the class, division or zone, group, and extent for a space
Area divider: A raised double member on a continuous deck that relieves thermal stress by breaking a large membrane field into sections; it does not allow movement
Area drain: A point inlet, a small grated drain at a single low spot that takes water down into a pipe
Array boundary: A code-defined line a short distance outside the array, commonly 1 ft, that splits the inside and outside voltage limits
As-built: The marked-up set showing what was actually built, maintained as the work goes in and used to produce record drawings at closeout [https://anvilfield.com/field-guides/glossary/as-built/]
As-built / record drawings: The drawings marked to show what was actually installed, including every field change, redlined as the work happens
As-built drawing: The construction set marked by the contractor to show what was actually installed, including every field change from the design
As-built model: The accurate digital record of what was actually built, the foundation the twin stands on
As-built verification: Overlaying the scan of installed work on the design model to find deviation, often as a heat-map
As-found / as-left: The recorded state of the equipment before and after the work
As-left reading: The measured value recorded at the close of a test, the baseline the building is re-tested against for the rest of its life
Asbestos / ACM: A group of fibrous minerals used in building products; asbestos-containing material is anything above the regulatory asbestos content
Asbestos / NESHAP: EPA National Emission Standards for Hazardous Air Pollutants, the federal rule governing asbestos in renovation and demolition, including the survey, abatement, and notification.
Asbestos survey: A pre-work building inspection by an accredited inspector that locates, samples, and reports asbestos-containing material
ASCE 7: The standard that sets design wind loads and the field, perimeter, and corner zones [https://anvilfield.com/field-guides/glossary/asce-7/]
ASD / VESDA: Aspirating smoke detection, the active method that draws air through sampling pipe to a high-sensitivity detector; VESDA is a common brand [https://anvilfield.com/field-guides/glossary/asd-vesda/]
ASHRAE 110: The tracer-gas test that proves hood containment by measuring how much tracer reaches a mannequin's breathing zone, run as-manufactured, as-installed, and as-used
ASHRAE 15: Refrigeration safety standard driving the machine-room detector, ventilation, and relief
ASHRAE 170 / FGI: ANSI/ASHRAE/ASHE Standard 170 and the FGI Guidelines, the governing requirement for healthcare ventilation, with a space-by-space table
ASHRAE 188: The standard requiring a written water management plan for Legionella risk
ASHRAE 241: ASHRAE Standard 241-2023, Control of Infectious Aerosols, which sets equivalent clean airflow requirements to reduce disease transmission risk
ASHRAE audit levels: Standard 211's three depths: Level 1 walk-through, Level 2 detailed survey, Level 3 investment-grade engineering.
ASHRAE recommended and allowable: The TC 9.9 intake envelopes; recommended is the efficiency aim, allowable is the outer limit, both at the intake
ASI: Architect's supplemental instruction; clarifies or makes a minor change to the contract documents without, by its terms, changing the sum or time [https://anvilfield.com/field-guides/glossary/asi/]
ASJ: All-service jacket, the factory facing on fiberglass that acts as a vapor retarder and protective skin
ASME B31.1: Power Piping, for higher-pressure and higher-temperature systems such as central plants
ASME B31.3: The Process Piping code that governs design, materials, fabrication, examination, and testing of process piping
ASME B31.9: Building Services Piping, the usual code for data center chilled-water and HVAC piping; sets the hydrostatic test at 1.5 times design pressure
ASME Section IV: The boiler code section for heating boilers: steam to 15 psig, hot water to 160 psi or 250 degrees F
ASME tank vs DOT cylinder: Permanent pressure-vessel tank refilled in place, versus a portable bottle filled or exchanged
ASP: Available static pressure for the duct, in inches of water column, after the components are subtracted from the rated external static
Aspect ratio: The width divided by the height of a rectangular duct [https://anvilfield.com/field-guides/glossary/aspect-ratio/]
Asphalt emulsion: Asphalt carried as droplets suspended in water; it breaks and loses the water to set, with no heat needed to place it [https://anvilfield.com/field-guides/glossary/asphalt-emulsion/]
Asphalt recycling: Reusing the existing pavement as aggregate, binder, or a stabilized base instead of hauling it off and buying virgin
Aspirator: The fan inside the detector that draws the sample and whose flow the system monitors for blockages and breaks
ASPIRE: The pipe-network modeling software for the VESDA family that calculates airflow, hole sizes, and transport time
ASR: Alkali-silica reaction, a slow expansive gel from reactive aggregate, alkali, and moisture
ASSE 1010: The performance standard for water hammer arresters with a permanently sealed cushion
ASSE 1051 / 1050: Product standards for individual and branch type AAVs (1051) and for stack type AAVs (1050)
Assembly: A bundle of the material and labor units for a repeated install, counted as one line
Asset marking / serial registration: Engraving or stamping an ID on tools and recording serial numbers so an item is harder to fence and can be matched on recovery
Asset utilization: How much an owned or rented asset is actually used versus sitting idle, used to right-size the fleet
AST: Aboveground storage tank, set on a pad, governed by NFPA 30 and 30A, UL 142, and SPCC
ASTM D7877: The standard guide for electronic methods of detecting and locating leaks in waterproof membranes, covering both voltage methods
ASTM D8231: The standard practice for a low-voltage electronic scanning system for detecting and locating membrane breaches
ASTM E1745 Class: Grade A, B, or C by tensile strength and puncture resistance; all classes are 0.1 perms or less
ASTM F1487: The consumer safety performance specification for public playground equipment, ages 2 through 12
ASTM F2200: The construction standard for the gate itself: openings, screening, exposed edges, and restraints
ASTM F3125: The consolidated bolt specification carrying A325, A490, F1852, and F2280 as grades
Aterm: Ampacity in the column matching the lowest-rated termination, usually 75 degrees C, per NEC 110.14(C)
Atmospheric / Category I: A gas unit that takes combustion air from the room and vents by natural draft up a vertical flue
ATP verification: Swab-and-luminometer test measuring adenosine triphosphate as organic residue in relative light units, to confirm cleaning was effective
ATS: Automatic transfer switch, which senses the loss of normal power and moves the load to the alternate source [https://anvilfield.com/field-guides/glossary/ats/]
Attached ledger: The bolted and flashed board that fastens an attached structure to the house, the same connection as a deck ledger
Attachment / anchoring system: A wet-glaze structural-silicone bead or a mechanical batten that ties the film edge to the frame so it resists, not just holds shards
Attic stock: The specified spare materials handed to the owner at closeout: tiles, lamps, filters, paint, keys, and the like
ATU / mound / pressure dosing: Alternative methods for poor sites: an aerobic treatment unit adds oxygen for higher treatment, a mound builds the field up in sand, pressure dosing pumps even timed doses to the field
Audio / wiretap consent: The legal requirement to obtain consent before recording audio, one-party or all-party depending on jurisdiction
Authorized employee: The worker who applies the lockout and performs the servicing on the equipment
Authorized scope: What the customer agreed to pay for, captured before the work
Automated irrigation / fertigation: The drip and recirculation that water the wall on a schedule, and the nutrient feed delivered through that water
Automatic gate operator: The powered motor and controller that opens and closes a gate on command, listed to UL 325
Automatic isolation valve: An actuated valve that closes on detection to stop the flow and isolate the affected loop or rack in seconds
Autonomous / machine-control equipment: Earth-moving equipment guided to a design surface by GPS, either semi-autonomous with an operator in the cab or fully autonomous with none
Autonomy: Battery runtime in minutes carrying the load, verified at design load
Autonomy / ride-through: How long the energy store carries the load before the generator does
Autotransformer: A transformer with primary and secondary electrically tied, sharing a winding, so it does not isolate
Auxiliary / emergency heat: Backup heat on a heat pump; aux stages in automatically, emergency forces it and locks out the compressor [https://anvilfield.com/field-guides/glossary/auxiliary-emergency-heat/]
Auxiliary gutter: A covered trough supplementing equipment locally, NEC Article 366, commonly limited to about 30 ft beyond the gear
Availability: The fraction of time or producible energy the plant was able to operate rather than sitting on a fault
Availability / MTTR: Availability is the percent of time the load was up, quoted in nines; MTTR is mean time to repair or recover, how fast operations restores after a failure.
Available fault current: The maximum current the supply can deliver into a bolted short at the panel location, a property of the install [https://anvilfield.com/field-guides/glossary/available-fault-current/]
Available fault current (AFC): The current a bolted fault can draw at a point, set by the utility, transformer, conductors, and motors
Available flow: What the meter, service line, and working pressure can actually deliver at the point of connection
Available static pressure: The rated external static left for the duct after the coil, filter, and grilles are subtracted
AVB: Atmospheric vacuum breaker; the simplest device, back-siphonage only, no continuous pressure, no downstream valve, non-testable (ASSE 1001)
Average ticket: Revenue per completed job; rises when good-better-best options are presented [https://anvilfield.com/field-guides/glossary/average-ticket/]
Averaging beam: A long ski reference that filters short bumps to smooth the ride
AVR: Automatic voltage regulator, which holds alternator voltage and is only fully tested under a reactive load
AWG: American Wire Gauge; the smaller the number, the larger the conductor and the allowance [https://anvilfield.com/field-guides/glossary/awg/]
AWG / kcmil: American Wire Gauge for smaller sizes, thousand circular mils for conductors above 4/0 [https://anvilfield.com/field-guides/glossary/awg-kcmil/]
AWI / AWS grade: The Architectural Woodwork Institute quality grade, Economy, Custom, or Premium, setting materials, joinery, tolerances, and finish; now paired with a separate duty level, 1 to 4
AWWA D102: The AWWA standard for coating the inside and outside of steel water-storage tanks
AXT (ANEXT / AFEXT): Alien crosstalk between adjacent cables in a bundle, near-end and far-end
Az: Net occupiable floor area of the zone, in square feet
B terminal: Thermostat terminal that energizes the reversing valve in heating, used by Rheem and some others
B&B (balled-and-burlapped): Field-grown stock dug with a soil ball wrapped in burlap and usually a wire basket [https://anvilfield.com/field-guides/glossary/b-b-balled-and-burlapped/]
Bac-t: The bacteriological test that clears a disinfected new service before it is connected, after the pressure test and the chlorine holding period
Back-end fabric: The high-speed, low-latency network connecting the GPUs for training; the largest link count in the cluster
Back-out plan: The written sequence to safely abort and restore the equipment to its starting state
Back-siphonage: Backflow caused by negative pressure in the supply pipe, which siphons water backward
Back-siphonage / backpressure: The two backflow mechanisms: a pull from negative supply pressure, or a push from higher downstream pressure
Back-stab vs back-wire clamp: A spring-clip push-in (avoid) versus a pressure plate driven by the terminal screw (acceptable)
Back-wire clamp: A screw-driven plate that clamps the conductor across a flat, stronger than a push-in back-stab
Backbone / horizontal: Backbone cabling connects distribution areas in a star; horizontal cabling runs from the HDA to the equipment
Backbone cabling: The cabling linking telecom rooms to each other and to the main room
Backdraft: Reverse flow that pulls combustion flue gas back down a vent into the space
Backdraft damper: A flap that closes when the fan is off to stop outside air from flowing back down the exhaust [https://anvilfield.com/field-guides/glossary/backdraft-damper/]
Backer rod: A compressible foam rope set below the sealant that breaks the bottom bond and sets the depth
Backfeed: Electricity flowing the wrong way out of the building onto the utility line, which can electrocute a lineman and destroy the generator [https://anvilfield.com/field-guides/glossary/backfeed/]
Backflow: Reverse flow of non-potable water into the potable supply, by back-siphonage or backpressure
Backflow preventer: The device that stops loop water, glycol, and inhibitor from flowing back into the potable supply
Backflow preventer (RPZ / PVB): The above-grade assembly that protects the potable supply, and the part most likely to crack if not winterized
Backlog: Work under contract but not yet built; sureties limit it against your capital [https://anvilfield.com/field-guides/glossary/backlog/]
Backpressure: Backflow caused by downstream pressure exceeding the supply pressure, which pushes water backward
Backpressure / backsiphonage: The two ways flow reverses: downstream pressure pushing back, or upstream vacuum pulling back
Backshore: A shore reset a small area at a time so the slab never deflects or takes up its own weight
Backup: The contemporaneous records, photos, dailies, tickets, deliveries, tests, that verify a billed line
Backwater valve: A check on below-grade drainage that stops a surcharged storm main from backing water up into a low area [https://anvilfield.com/field-guides/glossary/backwater-valve/]
BACnet: ANSI/ASHRAE Standard 135, the vendor-neutral building automation protocol, with BACnet/IP and MS/TP transports and an object model
BACnet (ASHRAE 135): The open, interoperable controls protocol; BACnet/IP and BACnet MS/TP physical layers
BACT: Best available control technology, the control level a major source must meet
Bacteriological test (bac-t): A lab test of a line sample for coliform and E. coli; no coliform is the pass that releases service
Bad debt: A receivable judged uncollectible and written off the books
Baffle / rafter vent: A rigid channel at the eave that holds insulation back and keeps the soffit intake open
Baffle / vent chute: A channel at the eave that keeps insulation off the intake and holds the air gap
Baffle filter: The listed grease removal device that turns the air sharply so grease droplets strike the blades and drain
BAg: Silver filler family for copper-to-brass and copper-to-steel joints; requires flux
Baghouse: The fabric-filter dust collector that catches fines and returns them to the mix
Balance point: Outdoor temperature where a heat pump's output equals the room's heat loss; below it the strip helps [https://anvilfield.com/field-guides/glossary/balance-point/]
Balanced border layout: Centering the grid so border tiles at opposite walls are equal and no narrower than about a half tile
Balancing valve: Valve on a return branch that sets each riser's recirc flow to hold temperature [https://anvilfield.com/field-guides/glossary/balancing-valve/]
Ballast: Stone or pavers laid over a loose membrane to hold it with weight, designed per ANSI/SPRI RP-4 [https://anvilfield.com/field-guides/glossary/ballast/]
Ballast bypass: Removing the ballast and wiring line voltage straight to the lamp holders for a Type B tube
Ballast rate: The weight of ballast per square foot the design requires, set by zone and given in pounds per square foot
Ballasted: Racking held down by weight with no membrane penetrations; heavier dead load
Ballasted racking: Solar or equipment racking held down by weight on pads instead of roof penetrations
Ballasted roof: A loose-laid single-ply roof held down by the weight of stone or concrete pavers instead of fasteners or adhesive
Balled-and-burlapped (B&B): A hand-dug ball wrapped in burlap and a wire basket to hold it together for the move
Bandwidth / IOPS / latency: Throughput in GB/s, operation count per second, and time-to-first-byte; the three numbers AI storage is sized to
Bar bending schedule (BBS): The table listing every bar by mark, size, grade, quantity, cut length, and shape
Bar mark: The unique identifier tying a schedule line to a bar on the placing drawing and a tag in the bundle
Bare metal: The NFPA 96 cleaning standard: the grease surfaces taken back to clean steel, not wiped
Barrier / mountable / roll curb: Curb shapes by face: vertical (barrier), sloped to drive over (mountable), or rounded (roll)
Barrier vs drainable EIFS: Barrier had no drainage and trapped water; drainable adds a WRB and a drainage gap behind the foam
Barrier-type device: A membrane or flap that opens to drainage and closes when dry, protecting the seal without adding water, listed to ASSE 1072
BAS / DDC: Building automation system; direct digital control, the digital controllers inside it
Base / ply sheet: The lower ply bonded to the substrate beneath the cap, usually smooth-surfaced
Base building / shell: What the landlord delivers: the structure, core, and systems brought to the suite, in a defined shell condition
Base course: The bottom asphalt lift; largest stone, the structural foundation of the bound layers
Base flashing: The roof material turned up a wall or curb that waterproofs the joint, commonly at least 8 in above a low-slope roof [https://anvilfield.com/field-guides/glossary/base-flashing/]
Base frame / foundation load: The frame and the surface that carry the whole load down to the ground or the structure without settling
Base plate, leveling, grout: The steel plate at the column base, set to elevation on leveling nuts or shims, with non-shrink grout packed under it for full bearing
Base scope vs enhancement: Recurring work in the fee versus extras billed on top
Base-8 / 12 / 24: Trunk fiber grouping; base-8 suits 8-fiber parallel optics with no stranded fibers, base-12 suits duplex and legacy
Baseline: The approved as-planned schedule, frozen as the reference everything is measured against
Baseline / M&V: The modeled counterfactual draw a curtailment is measured against, and the verification that certifies it
BAT: Backflow assembly tester, the person certified to test and submit, often on a two to three year renewal
Batch ticket: The delivery ticket recording the mix, quantity, and batch time; the legal record of the load
Bathroom group: The fixtures of one bath, a water closet, a lavatory, and a tub or shower, the unit a wet vent serves
Battens: Horizontal strips the tile hangs on and fastens to, raised on counter-battens or notched so water drains under the tile
Batter / setback: The backward lean built into a wall so it tips into the hill, not away from it
Battery backup: A DC pump run from a stored deep-cycle or AGM battery when the primary loses power or fails
BBS: Bar bending schedule, the table of every bar by mark, size, length, shape, and quantity
BBU: Battery backup unit, a rack-level battery that rides the load through a disturbance and the transfer to backup generation
BCM: Branch circuit monitoring, per-breaker current and power metering reported to the EPMS or DCIM [https://anvilfield.com/field-guides/glossary/bcm/]
BCuP: Copper-phosphorus filler family, self-fluxing on copper-to-copper joints; common in refrigeration
BCuP filler: Copper-phosphorus brazing alloy used without flux on copper-to-copper medical gas joints
Beam spread: The angle of a fixture's light cone in degrees; narrow for tall subjects, wide for broad ones
Bearing capacity: The pressure the soil can carry before it fails or settles too much, in psf [https://anvilfield.com/field-guides/glossary/bearing-capacity/]
Bearing pad: An elastomeric pad at a support that spreads the load and lets the member rotate and move
Bearing plate: A steel plate set in the wall and backed by blocking that supports a lighter fixture independent of the wall finish
Bearing stratum: The firm soil layer the helices must reach to develop the design capacity; the depth to it is set by the soil, not the drawing.
Bedding sand: The screeded 1 in (25 mm) setting course of washed ASTM C33 concrete sand the pavers seat into [https://anvilfield.com/field-guides/glossary/bedding-sand/]
Before / after: A photo pair showing a subject before and after work or correction, ideally from the same angle, proving the change or the fix
Before-cover-up: A photo taken in the last moment work is visible, before concrete, drywall, ceiling, or backfill permanently conceals it
Behind-the-meter (BTM): On-site generation behind the utility meter, used to power a site without the grid queue
Belled / under-reamed base: An enlarged base cut wider than the shaft to spread end bearing over more area, where the soil holds the shape
Belleville washer: A conical disc spring on the joint bolt that holds clamping force through thermal cycling
Bellows: The flexible membrane loop over a closed-cell foam core that compresses and stretches to absorb the joint's movement, commonly EPDM at 60 mil
Belly: A sag in the line that holds water; cleaning does not fix it
Belly / back-pitch: A sag or reverse grade in the line; a grade defect trenchless does not fix
Belly / sag: A low spot where the pipe lost slope and holds water and debris
Belt tracking: Keeping the belt centered; the belt moves toward the end of the roller it contacts first, so square and level control it
Belt vs roller vs screw: Belt carries on a moving belt, roller on driven or gravity rollers, screw on an auger flight in a trough
Benchmark: A point of known elevation, tied to the project datum, used as the reference for all vertical layout [https://anvilfield.com/field-guides/glossary/benchmark/]
Benchmark / datum: The fixed known elevation every grade on the site is measured up or down from
Bend deduction: The amount subtracted at each bend because the bar's true length is shorter than the summed outside legs
Bend radius: The tightest curve a cable allows before performance degrades, larger under pulling tension
Bending space: The clear depth a conductor needs to turn into a terminal without over-bending, from the wire-bending table
BEP: BIM execution plan: the agreement on who models what, to what LOD, on what schedule, and to what standards [https://anvilfield.com/field-guides/glossary/bep/]
BESS: Battery energy storage system, a large grid-interactive battery for energy, peak shaving, and grid services [https://anvilfield.com/field-guides/glossary/bess/]
BESS / PCS: Battery energy storage system and its power conversion system, the inverter that moves energy in and out
Best efficiency point (BEP): The flow at which a pump runs at peak efficiency, quietest, and with the least wear; select the duty point near it
BFM: Bonded fiber matrix, a high-strength sprayed mulch that bonds to soil; ~3,500 lb/acre, 24 to 48 hr cure
BIA: Business impact analysis, ranking systems by the impact of their loss and setting each one's RTO and RPO
Bid bond: Guarantees you will sign at your bid and provide the P and P bonds if awarded
Bid list: The set of prequalified contractors a GC or owner invites to bid a specific project
Bid/no-bid (go/no-go): The decision, before estimating, of whether to pursue a job at all
BIL: Basic impulse insulation level, the impulse voltage withstand of the insulation in kV [https://anvilfield.com/field-guides/glossary/bil/]
Bill of lading (BOL): The carrier's legal record of the shipment and its condition; the place exceptions are noted at delivery
Billable hour: An hour you can actually invoice, distinct from a paid hour; the rate is built on billable hours
Billable utilization: Share of paid field hours that land on billable work
BIM: Building information modeling, the construction model used to design, coordinate, and build the project, which feeds the twin
BIM vs VDC: BIM is the information-rich 3D model; VDC is the process of using that model to plan, coordinate, and build the work
Binder / emulsion: The sprayed asphalt that holds the chips; commonly a rapid-setting emulsion like CRS-2 or HFRS-2
Binder / intermediate course: The structural mix lift between surface and base; coarser, carries load and levels
Binder grade bump: Dropping the virgin binder one grade softer to offset the stiffness RAP adds to the blend
Binder plus EPDM / SBR: Polyurethane glue carrying colored EPDM top granules and recycled SBR base granules
Binding constraint: The first resource to run out, which caps the whole room no matter how much of the others is open
Biocide: A treatment that controls bacteria and slime, which clog passages and drive under-deposit corrosion, especially in glycol loops
Biocide / biofouling: Biofouling is biological growth and biofilm in the loop; the biocide is the additive that kills it before it forms
Biofall: Biological waterfall filter at the head of the falls that grows nutrient-eating bacteria
Biofilm: The bacterial film of soap, skin, and food in a drain that smells like sewage but is the drain, not the sewer
Biohazard remediation: Cleaning and decontaminating a scene fouled with blood, bodily fluids, sewage, or other infectious material so it is safe to use again
Bioretention soil media (BSM): The engineered sand-dominant filter mix, not topsoil or native soil
Biosolids: The treated, stabilized solid byproduct of wastewater treatment, handled for land application, landfill, or incineration
Biotic stress: Damage from living causes, insects and diseases, usually secondary to an already stressed plant
Biotic vs abiotic: A living cause (insect, disease, weed) versus a non-living one (drought, compaction, salt, chemical)
Bird stop: A formed eave closure that seals the open ends of a high-profile tile against birds, pests, and wind-driven rain
Birdbath: A low spot in the finished patch that ponds water and pumps it into the joint [https://anvilfield.com/field-guides/glossary/birdbath/]
Bitumen: The waterproofing asphalt or coal-tar pitch mopped between and over the plies
Bituminous stabilization: Binding pulverized FDR material with asphalt emulsion or foamed asphalt
Blackwater: Wastewater from toilets and urinals, and in most codes the kitchen and dishwasher
Bladder tank: An expansion tank with a replaceable bladder that holds the water off the steel shell, separate from the air charge
Blameless post-mortem: The review that focuses on the systemic conditions that allowed the incident, never on punishing an individual, so people tell the truth
Blank-off vacuum: The deepest vacuum a pump can pull with its ports capped; a check on the pump and its oil
Blanket PO / release: A standing PO at an agreed price for a project, drawn down by individual releases as needed
Blanking panel: A filler that closes an empty rack-unit slot so air passes only through equipment, not around it [https://anvilfield.com/field-guides/glossary/blanking-panel/]
Blast freezer: A zone that freezes product fast with very low air temperature and high airflow.
Bleed / blowdown: Wasted flow that holds down mineral concentration in the sump, the same idea as tower blowdown
Bleed rate: The rate at which water rises to the surface as solids settle; when evaporation beats it, the surface cracks
Bleed water: Water that rises to the surface as solids settle, which protects the skin until it leaves or is removed [https://anvilfield.com/field-guides/glossary/bleed-water/]
Bleed-blocking primer: A primer that keeps asphalt or bitumen from staining up through a light-colored coating
Bleed-out: The bead of melted bitumen squeezed out at a lap, the visual proof the seam fused
Bleeding / flushing: Binder rising through the chips to a slick black film, the too-much-binder failure
Blend: Two or more cultivars of the same grass species planted together
Blind / blank: A solid plate isolating the test section at a boundary, used instead of relying on a valve seat
Blind spot / blind zone: The area around equipment the operator cannot see, largest directly behind a backing machine
Blind spot / kill zone: The area around a machine the operator cannot see, and the close-in ground where an unseen worker on foot is most likely to be struck, especially behind a backing machine.
Blindside / pre-applied: Membrane installed before the pour, against shoring or a mud mat, bonding to the concrete
Blister: A small hollow bump from bleed water or air trapped under a prematurely sealed surface
Block cracking: A grid of large rectangles across the surface from binder shrinkage and aging; non-load, surface-fixable
Block load: A large load step applied at once to test voltage and frequency dip and recovery
Blocking: Solid backing inside the wall framing, set before the drywall, that the cabinets and wall-hung work anchor into
Blocking / backing: Wood or steel set in the open wall at rough-in to give grab bars and wall-hung fixtures something solid to anchor to
Bloodborne pathogens / 1910.1030: Infectious agents in blood such as HBV, HCV, and HIV; 29 CFR 1910.1030 is OSHA's standard for occupational exposure to them
Bloom succession: Overlapping flowering so forage is continuous from spring through fall, with no dead months
Blow count: The number of hammer blows to advance the pile a foot or an inch, the field read on capacity
Blow-out: Pushing compressed air through each zone to force the water out through the heads before the freeze
Blowdown: Water bled from the loop to hold dissolved solids in range [https://anvilfield.com/field-guides/glossary/blowdown/]
Blowdown / bleed: Water purged on purpose to keep dissolved solids from concentrating without limit [https://anvilfield.com/field-guides/glossary/blowdown-bleed/]
Blower-door test / ACH50: A calibrated fan test of air leakage at 50 pascals; ACH50 is air changes per hour at that pressure
Blowout: Sudden failure of a wall form when an overloaded tie lets go and the failure unzips along the form
Blue top: A grade hub set with its top at finished grade, marked blue for the operator to blade to
Blue-green roof: A detention layer below a vegetative roof, combining stormwater control with green-roof benefits
Blushing: A milky white haze in the sealer from over-application or sealing over trapped moisture
BMP: Best management practice, a physical or operational measure that prevents erosion or captures sediment, structural or non-structural [https://anvilfield.com/field-guides/glossary/bmp/]
BMS: Battery management system, the electronics that monitor, balance, and protect lithium cells and report state of health [https://anvilfield.com/field-guides/glossary/bms/]
BMS / BAS / DDC: Building management or automation system, the supervisory layer; direct digital control, the field controllers and logic underneath it
BMS / DCIM integration: Tying the detection to the building and data center management systems so a leak alarms, locates, and drives a shutdown
BOD: Basis of design, the design team's documented assumptions and decisions for how the design meets the OPR
Boil / quick condition: Upward seepage lifting and floating the soil grains so the excavation floor loses strength
Boiler horsepower: A steam output unit, about 33,475 Btu per hour per boiler horsepower
Boiling point: The temperature at which the fluid changes to vapor; chosen to hold the chip in band, per the fluid data sheet
Bolted vs arcing current: Bolted fault current is the dead-short value; arcing current is the lower current that actually flows through the arc
Bond beam: A horizontal grouted, reinforced course built in channel units, continuous through the wall [https://anvilfield.com/field-guides/glossary/bond-beam/]
Bond breaker: A release agent on the casting slab that keeps the cast panel from bonding to the slab so it lifts clean [https://anvilfield.com/field-guides/glossary/bond-breaker/]
Bond premium: The fee for the bond, about 1 to 3 percent of the contract, earned by the surety rather than held against claims
Bond strength: Adhesion and cohesion of SFRM to the steel, tested to ASTM E736, with the IBC minimum rising by building height [https://anvilfield.com/field-guides/glossary/bond-strength/]
Bonded / unbonded: Bonded strands are grouted to the concrete in a duct; unbonded slide free, anchored only at the ends
Bonded-flange drain: Surface drain whose flange the bonded or liquid membrane laps onto and seals to
Bonding: Permanent joining of metal parts to establish electrical continuity, for equal potential and a fault path back to the source
Bonding adhesive: Contact adhesive that glues the membrane to the substrate on a fully adhered roof, not a seam product
Bonding agent / bond coat: The primer or cementitious slurry that helps the topping knit to the profiled slab
Bonding bushing: A bushing with a lug or setscrew to land a bonding jumper, used to carry the ground around a concentric or eccentric knockout
Bonding capacity: The single-project and aggregate dollar limits a surety will guarantee for a contractor, built off working capital and equity [https://anvilfield.com/field-guides/glossary/bonding-capacity/]
Bonding distance: The calculated separation within which metal must be bonded to the LPS to prevent side flash
Bonding grid: The conductive plane around the pool, the shell steel or a copper conductor grid, that parts bond to
Bonding lug: The provided terminal on a pump motor or fitting where the bonding conductor lands
Bonding resistance: Resistance of the connection between two metal parts, in milliohms
Boom lift: Articulating or telescopic MEWP that extends the platform out and up beyond the base
Boom pump: Truck-mounted pump with a hydraulic, remote-controlled arm carrying the line to the placement
Booster heater: A heater that raises a high-temperature dishmachine's final rinse water to the sanitizing temperature, commonly near 180 F per the NSF listing
Booster pump: A pump set that raises the incoming supply pressure to a setpoint to reach fixtures the street pressure cannot serve
Box fill: The cubic-inch volume count for small device and outlet boxes under 314.16, a separate calculation [https://anvilfield.com/field-guides/glossary/box-fill/]
Box pusher: A containment plow with end plates that carries snow straight ahead without spilling off the sides
Brace insert: Cast-in hardware in the panel that the temporary brace bolts to, placed per the bracing drawing
Brace rod: Threaded steel rod through a union, split, or crack to bolt the parts directly together
Braced bay: A bay with wind bracing designed into it, erected first as the stable, plumb reference for the rest of the building
Brake horsepower (BHP): The power the fan demands at the shaft, varying with the cube of speed
Branch box: The distribution box on some multi-zone systems that splits refrigerant out to each head
Branch circuit: Conductors from the final overcurrent device to the outlets or load
Branch collar: The swollen ring of tissue where a branch meets the trunk, where the tree seals the cut; the cut goes just outside it
Branch controller: The valved box (refnet or BC unit) that splits refrigerant and sets each zone's mode on a heat recovery system
Branch interval: One story of height on a stack, the vertical space where a horizontal branch connects
Brazing: Joining copper with a filler melting above about 840 F, stronger than solder, with a nitrogen purge on refrigeration and medical gas
Breach: A hole, puncture, open seam, or other discontinuity in the membrane that lets water and current through
Break / cure: The emulsion turning from brown to black as water leaves; paving before it breaks traps water and kills the bond
Break / set: When the emulsion's water separates and leaves the asphalt to cure and grab the stone
Break and set: The point the emulsion releases its water and the mix gains strength; by evaporation for slurry, by chemistry for micro
Break tank: An intermediate tank that interrupts the static column and isolates the supply
Break-even: The price, or markup, that just covers direct cost plus the job's share of overhead, with zero profit. Below it the job loses money.
Breakaway connection: Listed duct-to-sleeve joint that releases in a fire so the duct cannot pull the damper out
Breakdown rolling: The first rolling phase, right behind the paver, that makes the bulk of the density while the mat is hottest [https://anvilfield.com/field-guides/glossary/breakdown-rolling/]
Breaking: Separation of the asphalt from the water in an emulsion, seen as the surface turning from brown to black
Breakout: A brittle concrete failure where a cone of concrete pries out around an anchor under load
Breather-drain: A rated device that equalizes pressure and releases condensate without breaking the rating
Bridge deck: The riding surface slab of a bridge, the element that takes traffic, water, chloride, and freeze-thaw and wears out first
Brine: Salt dissolved in water and sprayed as a liquid, the common anti-icing material
Broadcast to refusal: Casting media into a wet coat until it will absorb no more and the surface looks dry
Broom finish: Fine ridges dragged into the floated surface for traction, the standard driveway finish [https://anvilfield.com/field-guides/glossary/broom-finish/]
Browse: Deer or rabbits eating foliage, stems, and buds; deer leave a torn ragged end, rabbits a clean angled cut
Browse line: An even height, around 5 to 6 ft, to which deer have eaten the lower canopy across a property, a sign of sustained pressure
Brush grommet: A sealed cable cutout fitting whose brush or gasket closes the floor opening around the cables [https://anvilfield.com/field-guides/glossary/brush-grommet/]
Btu/h and ton: Load is in Btu per hour; one ton of cooling equals 12,000 Btu per hour
Btu/h, MBH, kW: Heat output: Btu per hour, thousands of Btu per hour, and kilowatts on metric or electric data
BTU/hr: British thermal units per hour, the appliance input rating on the nameplate
BTU/hr and MBH: Appliance input as heat per hour, MBH meaning thousands of BTU/hr
BTU_in: Heat input in BTU per hour, from the burner rating or the electric element wattage converted to BTU/hr
Buck / boost: Buck lowers the supply voltage, boost raises it, by a fixed percentage set by the connection
Bucket / unit: The removable plug-in module that holds a starter, drive, or feeder and stabs onto the vertical bus
Buddy punching: One worker clocking in or out for another who is not present, a common source of time leakage
BUG: Backlight, uplight, glare rating for outdoor luminaires
Building drain: The lowest interior drainage piping, extending a short distance outside the wall where the sewer begins
Building drift: The slow loss of design performance as setpoints, schedules, and sequences are overridden over time
Building envelope: The shell separating conditioned space from the weather: walls, roof, floors, windows, and the joints between them
Building pressurization: The air pressure inside a building relative to outdoors, set by the air balance
Building sewer / lateral: The buried gravity pipe from the building drain to the public main or septic tank
Building storm sewer: The storm pipe from the building wall to the site storm system, detention, or daylight
Building-related illness: A specific, diagnosable condition with an identifiable building cause, such as Legionnaires' disease
Bulb charge: The fluid sealed in the TXV bulb and power head, matched to the refrigerant, that sets the opening force
Bulk / main tank: The large on-site tank that stores the full Class runtime of fuel, often with margin above the bare runtime
Bull float / darby: Wide float run right after screed to flatten and embed aggregate before bleed water
Bump test: A quick before-use check that exposes the detector to gas to prove the sensors and alarms respond [https://anvilfield.com/field-guides/glossary/bump-test/]
Bunch-type grass: A grass that grows in clumps and does not spread to fill bare spots, so it is overseeded to stay full
Bundle: The unit shingles ship in; about three bundles cover a square for standard architectural shingle
Buoyancy anchoring: Deadmen and a hold-down pad with straps that keep an empty UST from floating out of the ground in groundwater
BUR: Built-up roofing, the multi-ply tar-and-gravel low-slope system of alternating bitumen and reinforcement [https://anvilfield.com/field-guides/glossary/bur/]
Burden: The load the CT secondary drives, the meter input plus the leads, which the CT is rated to supply
Burdened labor rate: Full hourly cost of a worker: wage plus taxes, insurance, benefits, and PTO, not the bare wage [https://anvilfield.com/field-guides/glossary/burdened-labor-rate/]
Burdened rate: The base wage plus labor burden (taxes, insurance, benefits), the true cost of an hour
Burn rate: How fast cash drops in a period; against the reserve it gives your runway in weeks
Burn-in: Sustained stress testing at full load over a set period to force early failures out before production
Burner / pan / orifice: The gas flame element, the tray that holds it and the media, and the metered gas opening sized to the fuel
Burnish / burn: Burnish is a hard polished trowel finish; burning is over-troweling that darkens the surface
Bus: The copper or aluminum bars the breakers connect to; its ampere rating is the panel's true capacity
Bus plug: A plug-in unit with a breaker or fusible switch that clamps onto the bus to tap a load
Busbar: High-current conductor running the height of the rack that carries the shelf's DC output to the trays via blind-mate connectors
Busway: Prefabricated busbar run, the common alternative to many parallel sets on high-amp feeders [https://anvilfield.com/field-guides/glossary/busway/]
Busway / bus duct: A prefabricated metal-enclosed run of bus bars in straight lengths and fittings, bolted into a continuous power path [https://anvilfield.com/field-guides/glossary/busway-bus-duct/]
Butyl seam tape: A polyester-reinforced butyl rubber tape that seals a lap or seam and must be top-coated, never left exposed
Bypass: Cold supply air that reaches the return without passing through a server, energy spent for no work
Bypass / recirculation: Supply air that returns uncooling, or hot exhaust that loops back to the inlet; both strand cooling [https://anvilfield.com/field-guides/glossary/bypass-recirculation/]
Bypass air: Cold supply that returns to the cooling unit without passing through any equipment, lowering the delta-T [https://anvilfield.com/field-guides/glossary/bypass-air/]
Bypass airflow: Cold supply that returns to the unit without passing through a server, doing no cooling work
Bypass damper: A relief damper that routes excess supply air back to the return when static climbs
Bypass orifice: The tiny hole, about 0.020 to 0.030 in, that repressurizes the upper chamber and shuts the valve.
Bypass-isolation: An ATS with a manual bypass that keeps the load up while the automatic switch is isolated for service
C: Conductor constant from the published point-to-point tables, larger for larger and lower-impedance conductors
C of O: Certificate of occupancy, the building department's clearance that a building may be occupied
C&D debris: Construction and demolition debris; separated at the source for diversion and recycling, with regulated material kept on its own manifested path.
C-wire (common): The conductor that gives the thermostat constant 24 V power
C13 / C19: IEC 60320 outlets for standard and higher-current server cords
C9 / C7: The large classic roofline bulb (C9) and its slightly smaller version (C7), sold as bulk line cut to length
C900: The AWWA standard for PVC pressure pipe used on water mains
ca1 / spacing: Edge distance from the anchor to a free edge, and the spacing between anchors
CAB: Change-advisory board, the group that reviews and approves planned changes
Cabinet ventilation / gas pooling: Vent openings that let leaked gas escape the enclosure; without them gas pools and can reach an explosive concentration
Cabinet width / depth: The enclosure footprint, commonly 600 or 800 mm wide and 1000 to 1200 mm deep
Cable fault: A break or disconnection in the sensing cable, reported separately from a leak by a supervised system
Cable rail deflection: The bowing of a tensioned cable under load that opens the gap, controlled by spacing, tension, and intermediate posts
Cable schedule: The master record, one row per link, carrying the identifier, both endpoints, media, length, pathway, and test result; the source the labels print from
Cable tray: A rigid support system that carries cables and conductors along a route in the open, governed by NEC Article 392
CAC: Cold-aisle containment, which encloses the cold supply aisle and lets the surrounding room run warm
CAC (cost to acquire a customer): Channel spend divided by the jobs it actually booked; the number that matters more than CPL
Cadence: The fixed rhythm of a recurring meeting, such as daily, weekly, or monthly, held at the same time
Cage / suite: A fenced enclosure or a walled room for one colocation customer's gear
Cage nut: Spring clip that snaps into a square rail hole to accept a mounting screw
Cage vs cabinet vs suite: A cabinet is a single enclosure; a cage is a fenced private area on the shared floor; a suite is a dedicated room
Calibrated torque tool: A torque wrench or screwdriver, click or dial type, that reads a known torque value and carries a current calibration certificate
Calibration: A scheduled adjustment of the sensor reading against a certified reference gas to correct drift [https://anvilfield.com/field-guides/glossary/calibration/]
Caliper: Trunk diameter used to size stock and estimate establishment time, measured 6 in up on small trees, 12 in on larger [https://anvilfield.com/field-guides/glossary/caliper/]
Callback: A return visit to a job already closed, to fix a problem under warranty. Costs parts, labor, drive and office time, and the billable work the tech could have been doing instead.
Callback / recall / comeback: A return trip to redo your own work that failed, on your dime, inside your labor warranty
Callback rate: Callbacks divided by jobs over a period, expressed as a percent, best sliced by tech and type
Callback triage: Sorting a warranty-period call into warranty defect, owner maintenance, or abuse to determine who pays
Calming inlet: An inlet turned up at the tank bottom so incoming water does not stir settled sediment
Candela (cd): The effective intensity of a strobe flash, set by room size and mounting per NFPA 72 tables
Cant strip: A 45-degree bevel at inside corners so the plies turn up the vertical without a sharp bend [https://anvilfield.com/field-guides/glossary/cant-strip/]
Cantilever: The joist overhang past the beam, limited to about one part overhang to four parts backspan
Cantilever slide gate: A slide gate carried on rollers with a counterbalance tail and no ground track
Cantilever vs braced: A cantilever wall is held by its embedment alone, while a braced wall adds tiebacks or struts when the cut is too deep for embedment to hold it.
Cap sheet: The top, granule-surfaced ply that faces the weather and takes UV and traffic
Capacity market: An ISO market that pays a resource for committing to be available to reduce load when called
Capacity test: A timed discharge at a defined rate to an end voltage, measuring delivered capacity against rating [https://anvilfield.com/field-guides/glossary/capacity-test/]
Cape seal: A chip seal with a slurry seal or micro-surfacing placed over it for a smoother surface
Capex: Capital expenditure: the up-front cost to build, including land, shell, power and cooling, and IT gear
Capillary gap: The small, even clearance between tube and fitting that lets molten filler draw into the joint
Capital plan: A multi-year forecast of roof actions and costs across the portfolio
Capital reserve: Money set aside on a schedule to fund the replacements the plan forecasts; a sinking fund for the roofs
Capping: Making the cylinder ends plane and square before the break, by bonded sulfur caps (ASTM C617) or unbonded pads (ASTM C1231)
Carbon equivalent (CE): A weighted measure of alloy content that drives preheat and crack susceptibility
Carbon monoxide (CO): A colorless, odorless, poisonous combustion gas, the deadly IAQ contaminant, checked first
Carbonation: Loss of concrete alkalinity as carbon dioxide reacts in over time, which depassivates the steel [https://anvilfield.com/field-guides/glossary/carbonation/]
Carpet tile: Modular carpet squares held with a tackifier, laid quarter-turn, monolithic, or ashlar
Carrier frequency: The IGBT switching rate, commonly 2 to 16 kHz, trading motor noise against drive heat and bearing current
Carrier studs: The threaded rods from the carrier finish kit that pass through the bowl flange and take the nuts holding the fixture to the wall
Casework: The cabinet boxes: base, wall, and tall units, the boxes that store and support
Cash flow: The money actually moving in and out of the account, distinct from profit on the P&L
Cash reserve: Money held on purpose, sized in weeks of payroll and overhead, to absorb slow stretches
Casing and grout (sanitary seal): The pipe lining the hole plus the grout sealing the annulus, which stops surface contamination from running down into the aquifer
Cast-in anchor: Anchor set in the forms before the pour: headed bolt, J or L bolt, or weld plate with studs [https://anvilfield.com/field-guides/glossary/cast-in-anchor/]
Cat 3 black water: The most contaminated water-restoration category, including sewage, grossly contaminated and carrying bacteria, viruses, and parasites
CAT rating: IEC category for transient overvoltage withstand; CAT III is a common HVAC floor, CAT IV for service-entrance work [https://anvilfield.com/field-guides/glossary/cat-rating/]
Cat6A: Category 6A copper tested to 500 MHz, the data center default for 10GBASE-T and PoE access
Catch basin: A grated box with a sediment sump and an outlet pipe, set at a low point to take surface water into a pipe [https://anvilfield.com/field-guides/glossary/catch-basin/]
Catch cup: An identical straight-sided container set on the ground to collect applied water during the test
Category 1 / 2 / 3: The contamination level of the water: 1 clean from a sanitary source, 2 gray with significant contamination, 3 black and grossly contaminated [https://anvilfield.com/field-guides/glossary/category-1-2-3/]
Category 1 / Category 5 test: Code-required functional safety tests: Category 1 is the annual no-load test; Category 5 is the five-year full-load test of safeties, governor, and buffers
Category IV: A positive-pressure, condensing appliance vented in plastic, with acidic condensate to neutralize
Cathodic corrosion protection: Sacrificial-anode or impressed-current protection that stops buried steel from rusting, tested to about negative 850 millivolts
Cathodic protection: Making the steel the cathode, by galvanic anode or impressed current, so the corrosion reaction at the bar slows to almost nothing [https://anvilfield.com/field-guides/glossary/cathodic-protection/]
Cathodic protection (CP): An electrical method that makes a metal structure the cathode of a circuit so it stops corroding and an anode corrodes instead
Caught-in/between: Worker crushed, pinned, or pulled into machinery, a collapse, or between objects
Cause-and-effect matrix: The document listing every initiating event against the exact outputs it drives, the script the EPO and fire tests run against [https://anvilfield.com/field-guides/glossary/cause-and-effect-matrix/]
CAV / VAV: Constant air volume (fixed airflow, varied temperature) and variable air volume (fixed cold supply temperature, varied airflow)
CAV vs VAV hood: Constant-air-volume pulls fixed airflow at all sash positions; variable-air-volume tracks the sash to hold a constant face velocity and save energy
Cavitation: Vapor bubbles forming and collapsing at the impeller when suction pressure falls below the water's vapor pressure, eroding the metal [https://anvilfield.com/field-guides/glossary/cavitation/]
Cavity wall vs veneer: Cavity wall is two wythes with a drained air space; veneer is a non-structural skin on a separate backup
CBA: Collective bargaining agreement, the union contract that governs wages, fringe, overtime, and travel on a union job
CBN: Common bonding network, all the building metal bonded together into one network connected to the grounding electrode system [https://anvilfield.com/field-guides/glossary/cbn/]
CBR: California Bearing Ratio, a subgrade strength measure relative to crushed stone, correlated loosely to Mr [https://anvilfield.com/field-guides/glossary/cbr/]
Cc: Chemistry coefficient, 1.0 for common cement types without retarders, higher for retarded or heavily blended mixes; verify against ACI 347
CCC: Current-carrying conductor, the count that triggers ampacity adjustment under 310.15, separate from the fill count [https://anvilfield.com/field-guides/glossary/ccc/]
CCD: Construction change directive (AIA G714); directs the contractor to proceed with a change before cost and time are agreed
CCID: Charging-circuit interrupting device, the EVSE's built-in ground-fault protection, commonly tripping at 20 mA
CCS / NACS (J3400): The two dominant North American DC connectors; CCS is the Combined Charging System, NACS is SAE J3400
CCT: Correlated color temperature in kelvin, the warmth or coolness of the light
CCT / CRI: Correlated color temperature in kelvin (warm to cool) and color rendering index on a 0 to 100 scale [https://anvilfield.com/field-guides/glossary/cct-cri/]
CCTV: Closed-circuit television, the general term for camera inspection of a pipe
CDE: Common data environment: the single cloud source of truth for the models and data, with version control so everyone is on the current model
CDU: Coolant distribution unit, the pumps, heat exchanger, filtration, and controls that condition and isolate the secondary loop [https://anvilfield.com/field-guides/glossary/cdu/]
CEC: Cation exchange capacity, the soil's ability to hold nutrients; low on sand, high on clay
CEC (meq/100g): Cation exchange capacity, the soil's nutrient-holding power; low on sand, high on clay
CEE / Ufer ground: Concrete-encased electrode: rebar or copper cast in an earth-contact footing, used as a grounding electrode
Cell / jar / string: A jar is one unit, cells wired in series form a string that builds the DC voltage
Cell and web: Cell is the hollow core that takes grout and rebar; web is the cross wall between cells
Cell tower / cell site: The structure and the equipment that radiate and connect a wireless cell: tower, antennas, radios, cable, grounding, and shelter
Cellular / foamed concrete: Low-density concrete made with engineered air from a foaming agent rather than aggregate
Cellular vs public-safety DAS: Cellular carries carrier phone signal as a service; public-safety carries responder radio as a code-mandated life-safety system
Central inverter / central battery: One UL 924 system feeding the emergency lighting circuits from a single battery bank
Central station: The staffed, often UL-listed station that receives signals, verifies them, and dispatches per the call list
Central UPS: The large uninterruptible power supply in the electrical room, the centralized alternative to distributed rack BBUs
Central vs decentralized: One plant serving the building, versus a unit at or near each zone
Ceramic vs porcelain tile: Both are fired clay. Porcelain is denser and absorbs 0.5 percent water or less, so it takes heavier traffic and freeze-thaw; ceramic absorbs more and suits lighter interior duty.
CERTA: NRCA Certified Roofing Torch Applicator, the torch-safety and fire-watch program
Certificate of destruction: The signed proof that a specific drive, by serial, was sanitized or destroyed and verified
Certificate of occupancy (CO): The AHJ document confirming the space meets code for its use and is legally safe to occupy [https://anvilfield.com/field-guides/glossary/certificate-of-occupancy-co/]
Certified installer: A contractor the manufacturer has approved and trained, required for system and NDL warranties
Certified payroll: The weekly report proving each worker was paid the required wage and fringe, with a signed Statement of Compliance [https://anvilfield.com/field-guides/glossary/certified-payroll/]
Certified renovator / firm: The individual trained and credentialed to direct lead-safe work, and the EPA- or state-certified company; both are required on a covered job
Cessation temperature: The mat temperature below which rolling no longer adds density, the bottom of the compaction window [https://anvilfield.com/field-guides/glossary/cessation-temperature/]
CFH: Cubic feet of gas per hour, the volume flow the pipe has to deliver
cfm: The pump's displacement, how fast it moves gas; sets pull-down speed, not the depth it can reach [https://anvilfield.com/field-guides/glossary/cfm/]
CFM / kW: Airflow per heat load; roughly 160 CFM per kW at a 20 F rise sets how much air a row needs
CFM / SCFM: Cubic feet per minute of air flow; SCFM is referenced to standard conditions
cfm per 100 sq ft: The unit of leakage rate, airflow lost per 100 square feet of duct surface area
CFM per ton: Airflow divided by cooling capacity in tons; about 400 is the comfort target [https://anvilfield.com/field-guides/glossary/cfm-per-ton/]
CGA connection: A Compressed Gas Association standard outlet, sized and threaded by gas, that prevents the wrong regulator hookup
CGP / NPDES: The Construction General Permit under the National Pollutant Discharge Elimination System, the permit that authorizes and conditions the stormwater discharge
CHAdeMO: Legacy DC connector on older Japanese EVs, commonly limited to about 100 to 150 kW
Chain of custody: The documented, unaltered path of a photo from capture to production, which supports its authenticity in a dispute [https://anvilfield.com/field-guides/glossary/chain-of-custody/]
Chair / bolster: Bar supports that hold the steel at the right height and cover, commonly within about 4 ft on center
Change order: Authorized addition to the scope, captured on the work order mid-job
Change order (CO): A written, signed agreement fixing the change in scope, contract sum, and contract time; the settled change [https://anvilfield.com/field-guides/glossary/change-order-co/]
Change schedule: Data-based interval for replacing gas and vapor cartridges before breakthrough, not based on odor
Changeover: A two-pipe arrangement that switches the whole zone between chilled and heating water seasonally; four-pipe avoids it [https://anvilfield.com/field-guides/glossary/changeover/]
Changeover / high limit: The condition at which free cooling locks out and mechanical cooling takes over
Changeover / high-limit: The setpoint that locks the economizer out when outside air is too warm or too humid to use
Changeover sensor: Supply-pipe temperature sensor that tells a 2-pipe controller whether the loop is hot or chilled
Channel: The full working path including patch cords and equipment cords, the connection the device actually sees
Channel / trench drain: A linear grate that catches surface water along a line across pavement or a doorway
Channel letter: A fabricated metal letter-shaped can holding LED modules, mounted to a wall or a raceway
Channel vs link: The link is the permanent horizontal cabling; the channel adds the patch cords and end connections
Char: The blackened, burned layer; char depth decides whether a structural member is cleaned and sealed or replaced
Charge generation: Static built by contact and separation of shoe and floor with each step
Chase: The thicker wall or service space that hides the carrier, the waste fitting, and the supplies, and provides service access
Chassis: The sealed working unit (compressor, coils, fans, heat) that slides into the sleeve and gets swapped
Checkpoint: A saved snapshot of the model and optimizer state, written periodically so a failed job restarts from it instead of zero
Chemical stabilization: Binding pulverized FDR material with cement, lime, fly ash, kiln dust, or a chemical agent
Chilled water / CHW: Cooling where a central chiller makes cold water that is pumped to coils in air handlers and fan coils
Chilled-water reset (CHWST): Raising the chilled-water supply setpoint when load and humidity allow, to cut chiller energy
Chimney drain: A vertical zone of clean, free-draining stone behind a wall that carries water down to the base pipe
Chip seal / BST: Sprayed asphalt binder with cover aggregate rolled in; a bituminous surface treatment or seal coat
Chip seal / scrub seal / cape seal: Sprayed binder with embedded chips; a chip seal broomed into the cracks; a chip seal covered by a slurry or micro-surfacing
Chloramines: Combined-chlorine compounds that off-gas from the water, sting eyes and airways, corrode metal, and are heavier than air
Chloride threshold: The chloride level at the steel above which the passive film breaks down and corrosion starts
Chloride-induced corrosion: Corrosion of reinforcing steel after chloride from road salt crosses a threshold at the bar and breaks its passive film
Chlorosis: Yellowing between the leaf veins, on turf usually from high pH tying up iron
Choke / bedding course: The thin finer open-graded stone that bridges the gaps and levels the surface without plugging the reservoir voids
Choke / stonewall: The high-flow limit on the map where gas reaches sonic velocity and flow cannot increase; rarely reached in chiller service
Choker / top course: The thin layer of fine material (DG or stone dust) screeded over the base so the turf rests on a tight plane
Choker layer: A thin coarse-sand layer between the rootzone and gravel that stops the sand washing down
CHP: Combined heat and power, capturing a generator's waste heat to raise total efficiency
Churn (shutoff / no-flow): The pump running against a closed discharge with no flow, reading its highest pressure; capped at 140 percent of rated pressure
Churn (shutoff): The no-flow condition where the pressure is highest, held to no more than 140 percent of rated
CIPP: Cured-in-place pipe, a resin tube cured inside the host to form a pipe within a pipe
Circuit setter / double regulating valve: A manual balancing valve set by hand with a memory stop and metering ports
Circuit vent: One vent serving a battery of 2 to 8 fixtures on a horizontal branch, used for rows of like fixtures
Circuit vs packet switching: Circuit sets up a path and holds it; packet makes a fresh forwarding decision for every packet. An OCS is circuit, a spine-leaf fabric is packet
Circular mil (cmil): Cross-sectional area unit used to take the proportional 250.122(B) increase when phase conductors are upsized
Circular-mil area: The conductor's cross-sectional area; paralleled conductors of a phase must match it
CISCA class: A spec's design concentrated load and the companion rolling, deflection, set, ultimate, and pedestal values; the values are manufacturer and spec specific
CJP: Complete joint penetration, a full-thickness groove weld, the usual UT-inspected case
CK1 / CK2: Check valve number one and number two, the independently acting checks inside the assembly
CL: Leakage class, the allowable leakage in cfm per 100 sq ft at 1 in. w.g. [https://anvilfield.com/field-guides/glossary/cl/]
Clamp meter: Reads current by clamping a conductor without breaking the circuit; captures running amps and inrush
Clamping drain: Two-piece drain that clamps a traditional liner; pairs with weep holes
Class: NFPA 110 class for runtime, the minimum hours at rated load without refueling [https://anvilfield.com/field-guides/glossary/class/]
Class / Division / Group: The material type (I gas, II dust, III fibers), the likelihood (Div 1 normal, Div 2 abnormal), and the specific material family
Class 1 to 4: The amount of water and evaporation load: 1 the least, 4 deeply bound moisture in hardwood, plaster, or concrete [https://anvilfield.com/field-guides/glossary/class-1-to-4/]
Class 2: A power-limited circuit fed by a listed Class 2 source, safe from shock and fire initiation
Class 2 / low voltage: An energy-limited circuit at 30 V or less under NEC Article 411, why 12 V buries shallow and splices safely
Class A / Class B: The two tension lap classes; Class B is the longer one, set by stress and how many bars splice at a section [https://anvilfield.com/field-guides/glossary/class-a-class-b/]
Class II road base: A graded crushed-aggregate base, fines to about 3/4 in, that compacts into a stable, draining foundation
Class of administration: TIA-606's four levels (Class 1 to 4) scaling the documentation burden from a single equipment room up to a multi-site enterprise
Classification: The employee-versus-independent-contractor determination, W-2 or 1099, set by law [https://anvilfield.com/field-guides/glossary/classification/]
Clay vs concrete tile: Clay tile is fired earth with color baked through; concrete tile is molded sand, cement, and pigment, usually heavier and prone to fade
Clean agent: A gaseous fire-extinguishing agent that leaves no residue, either a heat-absorbing halocarbon or an oxygen-lowering inert gas [https://anvilfield.com/field-guides/glossary/clean-agent/]
Clean-as-you-go: Removing debris and hazards continuously as part of the task, not in a scheduled blitz
Clean-in-place: Cleaning contents where they sit, without removing them, when the damage is contained
Cleaning verification: The RRP cleanup endpoint: a damp white cloth wiped on surfaces and compared to the EPA verification card, distinct from lab dust-wipe clearance
Cleanout: A capped access fitting on a drain line; a missing or loose plug is a direct opening for sewer gas [https://anvilfield.com/field-guides/glossary/cleanout/]
Cleanout (CO): A capped access fitting in a drain line for running a cable or jet to clear a stoppage
Cleanout (FCO/WCO): Capped access for rodding the line; floor cleanout or wall cleanout
Cleanroom: A room controlled to a defined airborne particle limit, classified and certified to an ISO 14644 class
Clear spacing: The gap between adjacent bars, at least the greatest of 1 in, a bar diameter, and 4/3 of the max aggregate
Clearance and creepage: Through-air and over-surface spacing between live parts, with minimums the standard sets by voltage
Clearance testing: Independent post-remediation verification, visual plus often air sampling, confirming the area is clean and dry
Clearance to combustibles: The required air gap between a hot grease duct and burnable construction, commonly 18 in unless reduced by a listed method [https://anvilfield.com/field-guides/glossary/clearance-to-combustibles/]
Clearance to grade: The gap from the siding to soil, roof, or deck, commonly about 6 in to grade, that keeps the cut edges off the wet
Clearing time: The time from the start of an arcing fault to the device opening and starving the arc; the variable every method shortens
Clearinghouse: The FMCSA database of CDL drug-and-alcohol testing violations, with pre-employment and annual query duties
Cleave angle: Angle of the cleaved end face from perpendicular; target under about 0.5 degrees
Clevis hanger: An adjustable horizontal hanger (MSS Type 1) that cradles the pipe between two side straps and a bolt
Climate zone: The code map that ties vapor retarder class and placement to the climate; Zones 6A, 7, and 8 are where NRCA flags vapor retarders
Clip spacing: The distance between clips, tightened at corners and edges for wind uplift
Clock to the job: Recording hours against a specific job and cost code, not a single daily in-and-out for the company
Clos / fabric: The non-blocking multistage topology, after Charles Clos, that spine-leaf applies to Ethernet
Close rate / conversion: The share of leads or quotes that turn into booked, sold jobs
Close rate / win rate: The share of presented proposals that turn into signed jobs
Closed loop: A sealed, buried HDPE loop of water and antifreeze that exchanges heat through the pipe wall
Closed system: A distribution made one-way by a PRV, check valve, or backflow preventer, so thermal expansion has nowhere to go without an expansion tank [https://anvilfield.com/field-guides/glossary/closed-system/]
Closed transition: Make-before-break transfer, with a brief source overlap and no interruption to the load
Closed-cell foam: Foam with sealed cells, giving low water absorption, strength, and about 6 to 7 R per inch
Closeout: The whole handoff: punch correction, documentation, training, warranties, spares, and the commissioning record turned over to the owner
Closeout package: The set of records and certifications delivered at closeout: as-builts, O&M manuals, warranties, releases, and certificates
Closet flange: The fitting that connects the toilet to the drain, set on top of the finished floor to seat the wax ring or gasket
Cloud / plugging / pour point: Temperatures where wax clouds the fuel, plugs the filter, and stops the fuel flowing, in that order as it cools
Cluster commissioning: Bring-up and proof of the GPU cluster: rack, fabric, GPU, and software, after the facility is commissioned
CM: Coupling multiplier, for the quality of the grip or handhold
CMA: Circular mil area of one conductor, for example 500,000 for 500 kcmil
CMMS: Computerized maintenance management system, the system of record for assets, work orders, schedules, and condition trends [https://anvilfield.com/field-guides/glossary/cmms/]
CMP: Communications plenum cable, listed for ducts, plenums, and environmental-air spaces, tested to the NFPA 262 plenum flame test
CMU: Concrete masonry unit, the precast concrete block; nominal 8 by 8 by 16, actual 7 5/8 by 7 5/8 by 15 5/8
CMV: Commercial motor vehicle, generally a vehicle or combination at 10,001 lb or more in interstate commerce, or carrying hazmat or 16-plus passengers
CO: Carbon monoxide, an odorless toxic gas often introduced by engines running near the opening [https://anvilfield.com/field-guides/glossary/co/]
CO air-free (COAF): Carbon monoxide corrected to remove diluting air, so combustion appliances compare honestly
Co-packaged optics (CPO): Optical engines integrated in the switch or NIC package next to the ASIC, instead of pluggable modules, for lower power
CO/ALR: Copper-aluminum revised, the listing for 15 and 20 A receptacles and switches rated for direct aluminum connection
CO2 as ventilation indicator: Indoor carbon dioxide above the outdoor level, a marker of outdoor air per person, not a toxin at normal indoor levels
CO2 as ventilation proxy: Carbon dioxide stands in for outdoor air per person, because exhaled CO2 builds up when ventilation cannot keep pace with occupancy
CO2 differential: Indoor CO2 above outdoor CO2, the value that tracks per-person ventilation, not a fixed 1000 ppm
Coagulation / flocculation: Coagulation neutralizes the charge on fine particles so they can stick; flocculation gently mixes them into settleable floc
COBie / structured data: A non-proprietary format for delivering equipment and asset data at handover in a form software can read
Code letter: Locked-rotor kVA per horsepower, the starting-inrush indicator
Code load (200 lbf concentrated): The 200 lbf load applied at any point on the top in any direction, plus a 50 plf uniform load, checked separately
CODIT / sealing: Compartmentalization of decay in trees, the tree walling off a wound rather than healing it back
Codominant stem / included bark: Two near-equal stems in a tight union with bark trapped inside it, a weak fork prone to splitting
Codominant stems: Two or more stems of nearly equal size from one point, with no single dominant leader
Codominant stems / included bark: Two equal stems from one point with bark turned inward at the union, a built-in weak plane prone to splitting
CODS: Critical operations data system, the 645 path that can omit the EPO under documented, supervised, AHJ-approved conditions
Coefficient of thermal expansion (α): How much a material grows per unit length per degree of temperature change
Cogged belt: A notched V-belt (AX, BX, CX) that flexes easier, runs cooler, and gains a little efficiency
Coherent optics: Optics that encode data in the light's amplitude and phase and use receiver DSP to recover it and compensate dispersion over distance
COI: Certificate of insurance summarizing the sub's coverage, limits, and expiration; coverage runs through the policy and endorsement, not the certificate [https://anvilfield.com/field-guides/glossary/coi/]
Coil stock: Flat aluminum sold in rolls, brake-bent to wrap the fascia as a low-maintenance cover
Cold / warm / powered shell: Bare enclosed structure, shell with core MEP installed, and shell with incoming power ready for tenant fit-out
Cold central plant recycling (CCPR): Cold recycling of RAP with emulsion or foam at a stationary plant, often from stockpiled RAP
Cold expansion: The PEX-a joining method under ASTM F1960, the tube is stretched over the fitting and shrinks to grip it [https://anvilfield.com/field-guides/glossary/cold-expansion/]
Cold feed: The bins and belt feeders that proportion aggregate before drying
Cold flow: Aluminum slowly creeping out from under clamping pressure, loosening the joint over time
Cold flow / creep: The slow movement of aluminum under a terminal as it heats and cools, which loosens the connection over time
Cold in-place recycling (CIR): Recycling the upper asphalt layer in place with emulsion or foamed asphalt, a partial-depth treatment
Cold joint: A weak plane where fresh concrete is placed against concrete that has already started to set [https://anvilfield.com/field-guides/glossary/cold-joint/]
Cold milling / cold planing: Grinding off the existing asphalt with a rotating toothed drum, no heat, to a set depth and slope [https://anvilfield.com/field-guides/glossary/cold-milling-cold-planing/]
Cold plate: The micro-channel block clamped to the chip that takes heat into the coolant; its channels are the most fragile part of the loop [https://anvilfield.com/field-guides/glossary/cold-plate/]
Cold roof: A deck held near outdoor temperature by air sealing, insulation, and ventilation so snow does not melt unevenly [https://anvilfield.com/field-guides/glossary/cold-roof/]
Cold springing: Installing the run short and under tension so it relaxes to neutral when hot
Cold storage / refrigerated warehouse: A building-sized insulated cold box served by a central refrigeration plant, holding product at cooler or freezer temperature.
Cold weather concreting: Placing and protecting concrete when the air is at or expected below about 40 F during the protection period, per ACI 306
Cold-plate microchannel: The fraction-of-a-millimeter passages inside the cold plate where the coolant takes heat off the chip; the least forgiving part of the loop
Cold-shrink: A pre-expanded rubber termination that contracts onto the cable under its own tension when the core is pulled, with no heat
Cold-shrink vs heat-shrink: Cold-shrink relaxes onto the cable when a core is pulled, no flame; heat-shrink is shrunk down with a torch
Cold-water sandwich: The cool slug between two hot draws on a tankless while the burner re-fires
Coliform: Indicator bacteria common in soil and gut; their absence is the accepted sign the line is microbiologically safe
Collective / NCCL: Group communication across GPUs such as all-reduce; NCCL is the common library whose bandwidth tests prove it
Colocation: Leasing space and power in someone else's facility, priced in dollars per kilowatt per month
Colocation (colo): Renting space, power, and cooling in a provider's data center while you own and operate the gear inside it [https://anvilfield.com/field-guides/glossary/colocation-colo/]
Color hardener (dry-shake): Pigment, sand, and cement broadcast on the fresh surface and floated in for surface color and a harder wear surface
Column fodder: A bid invited only to fill the count, with no real chance of winning
Combination fire/smoke damper (FSD): Does both: closes on a smoke signal with a heat backstop; listed to UL 555 and UL 555S
Combination meter-main: One outdoor enclosure with the meter socket and the service disconnect together
Combination starter: Disconnect, short-circuit protection, contactor, and overload in one assembly, as in an MCC bucket [https://anvilfield.com/field-guides/glossary/combination-starter/]
Combination waste-and-vent: An oversized, shallow-slope horizontal drain that vents itself, used for island sinks, sinks, lavatories, and floor drains
Combination-type AFCI: An AFCI that detects both series arcs and parallel arcs, the type the code generally requires
Combined sewer: An older public sewer carrying both storm and sanitary in one pipe, now largely replaced by separate systems [https://anvilfield.com/field-guides/glossary/combined-sewer/]
Combustible clearance: The manufacturer-required distance from a grill or burner to combustible construction, held with a non-combustible enclosure
Combustible scrap: Burnable debris such as packaging, sawdust, and felt that has to be cleared at regular intervals
Combustibles: Materials that can ignite and burn, cleared within about 35 ft of the work or covered with fire-resistant blankets and shields
Combustion analysis: Measuring flue-gas O2, CO, and temperature plus draft with a calibrated analyzer to read excess air and efficiency and confirm safe, clean combustion
Combustion analyzer: Reads flue-gas O2, CO, and temperature and calculates efficiency and CO air-free for gas-fired equipment
Comfort / crossover valve: A thermostatic valve bridging hot to cold under the far fixture in a return-less retrofit
Commercial ice machine: A refrigeration system that freezes potable water into cube, nugget, or flake ice for food service, healthcare, and industry
Commercial kitchen equipment install: Coordinating gas, electric, water, drain, and ventilation to land where each appliance goes, then hooking each appliance up to code and to NSF
Commercial refrigeration: Systems that keep food and product cold in walk-in coolers and freezers, reach-ins, and supermarket racks, using the vapor-compression cycle at low temperatures under near-continuous duty
Commissioning (Cx): Verifying the installed system performs to the design intent, often by a third-party agent [https://anvilfield.com/field-guides/glossary/commissioning-cx/]
Commissioning authority (CxA): The independent expert who runs the commissioning process for the owner
Common / traveler: On a 3-way switch, the common connects to hot or load, the travelers run between switches
Common data environment (CDE): The single agreed place where project documents and data are collected, managed, and shared, per ISO 19650
Common vent: A single dry vent serving two fixtures whose drains connect at the same point, on the same floor
Common-mode noise: Noise appearing between the grounded conductors and ground, as opposed to between the line conductors
Common-mode voltage: Voltage the whole motor sees to ground from PWM switching, the source of shaft and bearing currents
Communicator / dual path: The device that carries signals offsite over cellular and IP; dual path so a failure of one does not silence the system
Compact roof: A low-slope assembly with insulation above the deck and no vent space below the membrane
Compacted thickness: The thickness of a layer after rolling, which is what a spec and a quote should mean
Compaction grouting: Pumping stiff, low-slump grout under pressure to displace and densify loose soil and fill voids, forming a bulb
Compaction window: The time and temperature range in which the mat can be rolled to density before it cools past stop temperature [https://anvilfield.com/field-guides/glossary/compaction-window/]
Compensating measure: A temporary protection put in place during an impairment, such as a fire watch, evacuation, or temporary water supply
Competency framework: The documented list of what each role must know and do, how it is assessed, and the sign-off to perform it alone
Competency sign-off: A mentor's verification that an apprentice has demonstrated a specific skill, dated and recorded
Competent person: Someone able to identify scaffold hazards and with authority to take prompt corrective action, including tagging it out [https://anvilfield.com/field-guides/glossary/competent-person/]
Competent vs qualified person: The competent person spots and corrects hazards and inspects the rig; the qualified person designs the rigging and anchors
Completed operations: GL coverage for damage that appears after you finished and left the job
Composite metal deck: A slab poured on corrugated steel decking; the steel pan reflects the radar and hides what is at or below it
Compound gauge: The manifold's low-side gauge; its vacuum scale stops near 30 in Hg, far short of the micron range
Compressed gas cylinder: A portable bottle holding gas at high pressure, often thousands of psi, with all that energy stored in a steel or aluminum shell
Compression tank: The older plain-steel tank with air and water in direct contact, which waterlogs over time and is drained to recharge
Compressive strength: Resistance to crushing under load, in psi, the cover board's protection against point loads
Concealed damage: Damage found after delivery with no external sign at the dock; the hardest freight claim to win
Concealed work: Buried or hidden work that can only be recorded before cover-up, after which the as-built is the only record
Concealed-arm carrier: A lavatory carrier with arms that project through the wall into the fixture body, carrying the lav load to the frame and floor
Concentrated (point) load: Load applied through a roughly 1 sq in indentor (1 in square or 1.128 in diameter), representing a rack foot or caster at rest [https://anvilfield.com/field-guides/glossary/concentrated-point-load/]
Concentrated / point load: Weight delivered through a small contact area, such as a rack foot or caster, checked separately from the uniform load
Concentric neutral: Bare wires wrapped helically over the insulation shield that serve as the metallic shield and the neutral on URD-style cable [https://anvilfield.com/field-guides/glossary/concentric-neutral/]
Concrete cover: The depth of sound concrete between the surface and the nearest reinforcing bar; the chloride barrier protecting the steel [https://anvilfield.com/field-guides/glossary/concrete-cover/]
Concrete dye: Fine, intense coloring particles that penetrate the surface; vivid but usually not UV stable, so interior-focused
Concurrent maintainability: The ability to service any component or path on a plan, with the IT load running, the Tier III behavior [https://anvilfield.com/field-guides/glossary/concurrent-maintainability/]
Concurrently maintainable: Every component and path can be serviced on a plan without dropping the load, the Tier III test [https://anvilfield.com/field-guides/glossary/concurrently-maintainable/]
Condensate: The water that forms when steam gives up its heat and condenses, returned to the boiler to be reused [https://anvilfield.com/field-guides/glossary/condensate/]
Condensate neutralizer: A media cartridge that raises the pH of acidic condensate before it goes to drain; the media is consumed and replaced over time [https://anvilfield.com/field-guides/glossary/condensate-neutralizer/]
Condensate pump: A float-driven pump that lifts condensate where gravity cannot drain it, with its own safety float
Condensate trap: The drain seal that lets a draw-through pan drain against the blower's negative pressure
Condenser: The coil or heat exchanger where the vapor gives up its latent heat and condenses back to liquid, rejecting heat to facility water
Condenser-water reset: Lowering the condenser-water setpoint to cut lift and chiller kW, traded against rising tower fan kW
Condenser-water reset (CWST / ECWT): Lowering the condenser-water setpoint to cut lift, traded against rising tower fan power
Condensing: Cooling the flue gas below its dew point so water vapor condenses and gives up latent heat, the source of high efficiency [https://anvilfield.com/field-guides/glossary/condensing/]
Condensing appliance: A furnace, boiler, or water heater that condenses flue-gas vapor to recover latent heat, making acidic condensate
Condition 1 / 2 / 3: How the depth is set by what is across the space: nothing grounded, a grounded surface, or live parts on both sides
Condition monitoring: Measuring a machine's vibration, heat, oil, or sound to assess its health while it runs
Conditional waiver: A lien waiver that takes effect only when the payment actually clears.
Conductive flooring: Reads at or below 1.0 x 10^6 ohms; drains charge fastest, with a lower bound for personnel safety near energized gear
Conductivity: The ionic content of the fluid in microsiemens per centimeter (uS/cm); held low to limit galvanic corrosion and as a contamination indicator [https://anvilfield.com/field-guides/glossary/conductivity/]
Conductor / leader: The vertical storm pipe carrying flow from a roof drain or scupper down through the building; conductor inside, leader often outside
Conductor fill: The summed area of all conductors as a fraction of the trough's interior area, held to 20 percent
Conductor head: The open box at the top of a leader that catches scupper or gutter flow and feeds it into the pipe with an air gap
Conductor head / leader head: The open collector box at the top of a downspout that catches and funnels flow and spills overflow
Conductor insulation: The cloth and rubber covering on the wire, distinct from attic thermal insulation
Conductors per phase: How many conductors share one phase, equal to the number of parallel sets
Conduit body: An access fitting in a conduit run with a removable cover for direction change, pulling, or access; also called a condulet or outlet body [https://anvilfield.com/field-guides/glossary/conduit-body/]
Conduit seal (EYS/EYD): A compound-filled fitting that blocks gas, vapor, and flame from traveling through the conduit between enclosures or across the boundary
Confined space: A space with limited entry and exit, not for continuous occupancy, that can develop a deadly atmosphere [https://anvilfield.com/field-guides/glossary/confined-space/]
Connected jobsite / IoT: A site instrumented with internet-connected sensors on people, equipment, materials, and the environment, feeding data to a platform
Connected load: The total CFH of all appliances the system can serve, summed for sizing [https://anvilfield.com/field-guides/glossary/connected-load/]
Connected twin: A model tied to live BAS, IoT, and asset data that mirrors current conditions
Connected vs demand load: The sum of all nameplate ratings against what the site actually draws with diversity and tapering
Consequence: The severity if a failed part hits the target, scaled negligible, minor, significant, or severe
Consistency / workability: How readily fresh concrete flows, places, and consolidates without segregating
Consolidation / compaction: Vibrating the entrapped air out of placed concrete so it is dense and void-free
Constant-wattage cable: Series-resistance cable with fixed output per foot; cannot overlap, needs a control
Constraint: Anything that must be in place before a task can be done: material, information, predecessor work, labor, equipment, space, or external items
Constructability: Whether the design can actually be built and sequenced, reviewed on paper before the conflicts reach the field.
Construction (cold) joint: The planned, non-moving joint between two concrete pours
Construction cash flow: The timing of money out for labor and material against money in from billing and collection; the company runs on it
Construction change directive (CCD): The owner's written direction to proceed with a change before price or time is settled [https://anvilfield.com/field-guides/glossary/construction-change-directive-ccd/]
Construction closeout: The final phase that transfers a complete, operable building and its records to the owner before final payment
Construction joint: A planned stop between two pours that bonds back to act as one element and transmits load across [https://anvilfield.com/field-guides/glossary/construction-joint/]
Construction layout: Transferring the design points, lines, and elevations from the drawings or model onto the ground and structure so each trade builds in the right place
Construction robotics: The use of robots and automated machines to do dull, dirty, dangerous, and repetitive jobsite work, augmenting the crew rather than replacing the trade
Construction wind speed: The reduced wind the temporary bracing is designed to, lower than the building's final design wind
Contact / noncontact lap: A lap with the bars touching, or separated by a small gap within the code spacing limit
Contact resistance / ductor: Micro-ohm measurement across a closed contact or joint; high means loose, corroded, or worn
Contact time / dwell: How long the condensate sits against the media; too little and the water under-treats
Containment: Doors and a roof that seal a cold or hot aisle so the two air streams cannot mix [https://anvilfield.com/field-guides/glossary/containment/]
Containment backflow: The backflow assembly at the service entry that protects the main from the whole building, an RP for high hazard or a DC for low hazard
Containment vs isolation: Protection at the service to guard the public main versus protection at each fixture to guard the building
Contemporaneous: Created at the time of the work by someone with knowledge, the quality that makes a record hard to challenge in a dispute [https://anvilfield.com/field-guides/glossary/contemporaneous/]
Contemporaneous record: A record made at the time of the event, the quality that makes the daily report credible in a claim
Contents pack-out: Removing a building's belongings off-site so the structure can be dried, cleaned, or rebuilt
Contingency: Money in the estimate for known-unknowns: costs that will occur but are not yet defined, sized to the project's risk and design completeness. Not profit, padding, or forgotten scope. [https://anvilfield.com/field-guides/glossary/contingency/]
Continuity: An electrically continuous path, confirmed as near-zero ohms end to end with a low-resistance ohmmeter or continuity tester [https://anvilfield.com/field-guides/glossary/continuity/]
Continuous cleat: A hooked metal strip fastened to the building that the edge metal's hemmed drip locks over for uplift resistance
Continuous commissioning: Replacing one-time commissioning with an ongoing process so drift is caught as it happens
Continuous cooling: Holding temperature through a power event and the transfer that follows, a Tier IV requirement that bites hardest on liquid [https://anvilfield.com/field-guides/glossary/continuous-cooling/]
Continuous exterior insulation (c.i.): Rigid board outside the sheathing that wraps the framing, breaks the thermal bridge, and warms the sheathing
Continuous feed: Metering chlorine into the fill so the whole line reaches at least 25 mg/L, held at least 24 hours
Continuous insulation (c.i.): Insulation running uninterrupted across the structure, what an above-deck board roof provides
Continuous load: A load expected to run at maximum for 3 hours or more, generally taken at 125 percent [https://anvilfield.com/field-guides/glossary/continuous-load/]
Continuous vs periodic: Continuous means the inspector observes the full time work is performed; periodic means part-time or at intervals, as the code tables and statement assign
Contraction (control) joint: A sawed plane of weakness that forces the shrinkage crack to a chosen line
Control / contraction joint: A planned weak line that makes concrete crack where you want it, within a single element, without separating it [https://anvilfield.com/field-guides/glossary/control-contraction-joint/]
Control joint: A manufactured break in the board that lets the wall or ceiling move so it cracks at the joint instead of through the finish [https://anvilfield.com/field-guides/glossary/control-joint/]
Control network: The surveyed set of reference points, control points for horizontal position and benchmarks for vertical, that everything is laid out from
Control stop: The angle stop at the supply that shuts off and trims flow to the valve; not the volume adjustment.
Control vs expansion joint: Control joint relieves CMU shrinkage; expansion joint relieves clay brick growth
Controlled conductors: The PV circuit conductors that rapid shutdown is required to de-energize
Controlled decking zone (CDZ): A bounded leading-edge area, 15 to 30 ft up and no more than 90 by 90 ft with under 3,000 sq ft unsecured, where trained deckers place metal deck under specific controls
Controller: The brain of the elevator: dispatching and the safety logic. The mod swaps obsolete relay logic for a microprocessor controller [https://anvilfield.com/field-guides/glossary/controller/]
Conversion / orifice: Changing the orifices and regulator so an appliance fires correctly on the new fuel
Conversion stage: Any AC-to-DC or DC-to-DC step; each loses some power as heat, so fewer stages raise efficiency
Conveyor / material handling: Machinery that moves product through a building, the broad trade covering belt, roller, chain, screw, pneumatic, overhead, and sortation
Cool roof: A reflective roof surface that lowers surface temperature and cooling load, rated by solar reflectance index [https://anvilfield.com/field-guides/glossary/cool-roof/]
Cool-season / warm-season: Grasses adapted to northern fall growth versus southern late-spring and summer growth [https://anvilfield.com/field-guides/glossary/cool-season-warm-season/]
Cool-season / warm-season annual: Cool-season annuals bloom in mild weather and decline in heat; warm-season annuals need warm soil and air and die at frost
Cool-season grass: Turf adapted to northern climates that grows best at 60 to 75 degrees F and can brown in summer heat [https://anvilfield.com/field-guides/glossary/cool-season-grass/]
Cooling class: Nameplate code for the cooling method (ONAN, ONAF, AA, FA)
Cooling maximum: The design airflow for the zone, the most air the box delivers on a full cooling call
Cooling module / skid: Prefabricated mechanical plant: chillers, pumps, heat rejection, and coolant distribution
Coordination time interval (CTI): The minimum time margin between two device curves, commonly about 0.3 to 0.4 seconds for relays, covering interrupting time, overtravel, and tolerance
COP: Coefficient of performance, heat moved divided by energy used; greater than 1 on a heat pump [https://anvilfield.com/field-guides/glossary/cop/]
COP / EER: Coefficient of performance for heating and energy efficiency ratio for cooling, both measured at rated EWT
COPALUM: The CPSC-recognized crimp repair that cold-welds a copper pigtail to the aluminum with a controlled tool
Coping: The sloped cap covering the top of a parapet wall, a wind-uplift item under ANSI/SPRI ES-1 [https://anvilfield.com/field-guides/glossary/coping/]
Copper bib: A small copper flashing slid under the courses above to shed water over a replacement slate's nail
Corbel: A haunch cast onto a column or wall that a beam or member bears on
Cord set: An extension cord or flexible cord assembly with attachment plug and connector, a primary item the program tests
Core: The old part carrying a refundable charge, returned to the supplier to collect the credit [https://anvilfield.com/field-guides/glossary/core/]
Core / slug: The cylindrical concrete plug left inside a hollow core bit when the hole is through
Core aeration: Pulling soil plugs to relieve compaction and open the soil to water and air
Core aeration (coring, hollow-tine): Pulling soil plugs out of the lawn with hollow tubes to relieve compaction and open the soil
Core charge: A deposit on a rebuildable part, refunded when the old core is returned
Core tools: Valves at the service ports that let you isolate the system from the pump and hoses to run an honest decay test
Core-removal tool: A valve that lets you take out the Schrader cores while the system stays sealed, removing a major flow restriction
Cores: Cut samples through the roof that confirm wet versus dry and verify survey readings
Corner bead: Metal, paper-faced, or vinyl reinforcement that straightens and protects an outside corner and gives a hard line to finish to
Corporation stop: The valve and fitting that taps the service into the main, threaded into the pipe or a tapping saddle (AWWA C800), the first shutoff on the service
Correction factor: The ambient temperature multiplier from Table 310.15(B)(1)
Corrective action: The fix put in place to prevent recurrence, ranked by the hierarchy of controls and tracked to verified closure [https://anvilfield.com/field-guides/glossary/corrective-action/]
Correlation: The relationship between ICMV and core density built on a test section, reported as a coefficient, that lets the ICMV map be read with confidence
Corrosion control: Utility treatment, often orthophosphate, that coats lead pipe to limit how much lead dissolves
Corrosion coupon: A clean strip of copper or silver placed in the space; the corrosion thickness on it sets the severity level [https://anvilfield.com/field-guides/glossary/corrosion-coupon/]
Corrosion inhibitor: The additive package that passivates the loop metals, such as azoles for copper, matched to the metallurgy and consumed over time [https://anvilfield.com/field-guides/glossary/corrosion-inhibitor/]
Corrosion-resistant rebar: Reinforcement that resists chloride attack: epoxy-coated, galvanized, stainless, or low-carbon chromium alloy bar
Cost code: The category within a job, such as rough-in, service, or trim, that an expense is tagged to [https://anvilfield.com/field-guides/glossary/cost-code/]
Cost code / phase: The label that splits a job into rough-in, trim, service, and other phases for estimate-vs-actual
Cost of bidding: The estimating hours and opportunity cost a bid consumes, won or lost
Cost of quality: Prevention plus appraisal (conformance) against internal plus external failure (rework and callbacks); failure cost dwarfs prevention
Cost per MW: Build cost per megawatt of IT capacity, the headline metric; varies widely by market and time
Cost to complete: An honest estimate of what it will take to finish the remaining work, not what is left in the budget
Cost-plus: A contract paid as actual cost plus an agreed fee, where every billed cost needs backup
Cost-to-cost: Cost incurred to date divided by total estimated cost at completion, the usual percent-complete input
Counter slope: The opposing slope of the gutter at the bottom of the ramp, commonly 5 percent maximum
Counterbalance: The spring system that offsets the door's weight so the door can be lifted with little force
Counterflashing: Metal that overlaps and covers the top edge of a base flashing so water sheds over the face instead of behind it [https://anvilfield.com/field-guides/glossary/counterflashing/]
Coupling: The quality of the grip or handhold on the load, one of the six lifting-equation factors
COV: Change of value, logging or reporting a point only when it moves past a threshold rather than on a fixed interval
Cove / detail: The membrane turned up at a wall or curb over a fillet, plus the reinforced treatment at drains, penetrations, and terminations
Cover: The depth of concrete from the surface to the reinforcing steel, which protects the bar and sets a shallow anchor's clearance
Cover aggregate / chips: The clean, single-sized stone spread onto the binder, sometimes precoated
Cover board: The dense board over the insulation that protects the membrane and gives it a bondable base
Coverage / yield: Roof area one gallon covers at a target thickness; theoretical is 1604 times solids over DFT mils
Coverage grid / DAQ: The floor divided into squares and measured for signal level and quality; DAQ is delivered audio quality, how clearly voice is understood
CPI: Cost performance index from earned value: earned value over actual cost; above 1.0 favorable, below 1.0 an overrun, the dollar version of the productivity factor
CPI / coalescing plate: Corrugated-plate separator whose inclined plates merge small oil droplets for better effluent in a smaller tank
CPL (cost per lead): Channel spend divided by the leads it produced
CPM: Critical path method: a schedule of logic-linked activities whose dates and critical path the software calculates from the relationships and durations
CPR: Cardiopulmonary resuscitation: chest compressions, with or without rescue breaths, to keep blood moving
CPSI: Certified Playground Safety Inspector, the NRPA credential for auditing a playground against CPSC and ASTM standards
CPT: Control power transformer, steps line voltage down to feed the control circuit, with primary and secondary fusing
CPT / SPT verification: Cone penetration and standard penetration tests run before and after treatment to confirm the soil actually improved
CPTED: Crime prevention through environmental design, securing a site through layout, sightlines, and lighting
CPVC: Chlorinated polyvinyl chloride, a rigid plastic pipe rated for hot and cold potable water
CRAC: Computer room air conditioner, a direct-expansion unit with its own compressor and refrigerant circuit [https://anvilfield.com/field-guides/glossary/crac/]
CRAC / CRAH: Computer room air conditioner (DX) and computer room air handler (chilled water), the room units that often carry humidity control [https://anvilfield.com/field-guides/glossary/crac-crah/]
Crack injection: Filling a crack from inside the section under pressure or by gravity, to bond it or seal it
Crack sealing vs crack filling: Flexible hot-pour into working cracks versus a stiffer material into non-working cracks
Crack width: The opening of a crack at the surface, one clue among timing, pattern, and location
Crack-bridging base coat: The base coat that provides the primary waterproofing and stretches over moving cracks without tearing
Cracked concrete: Concrete in a tension zone that cracks under load; an adhesive must be qualified for it to be used there
Cracked-concrete rated: Qualified to hold rated capacity in concrete cracked through the anchor, required for seismic
CRAH: Computer room air handler, the chilled-water air mover whose fans are commonly kept on generator or UPS during the gap [https://anvilfield.com/field-guides/glossary/crah/]
CRAH / CRAC: Computer room air handler (chilled water coil) or air conditioner (DX with a compressor); in-row units come in both forms
Crazing: A shallow random map of hairline cracks under about 1/8 in deep; cosmetic, from fast surface drying
CRCP: Continuously reinforced concrete pavement; heavy continuous steel, no transverse contraction joints
Credential / reader: The credential is what a person presents (card, fob, smart card, phone, PIN, or biometric); the reader reads it and sends it to the controller
Creep corrosion: Corrosion product from sulfur or chlorine gases that creeps across a board and bridges adjacent features
CRI: Color rendering index on a scale to 100, how faithfully the light shows color
Cricket: A built-up slope on the upslope side of a curb that diverts water around it
Cricket / saddle: A raised, sloped diverter built behind or around an obstruction to split water past it instead of ponding [https://anvilfield.com/field-guides/glossary/cricket-saddle/]
Critical facilities: The power, cooling, and supporting systems whose failure stops the load, and the people and program that keep them running
Critical facilities operations: The team that runs and watches the physical plant that keeps IT alive: power, generators, UPS, switchgear, cooling, and the room environment.
Critical fall height / impact attenuation: Fall height is highest play surface to the surface below; critical height is the rating from the ASTM F1292 head-injury test, and it must meet or exceed the fall height
Critical lift: A lift with extra consequence or less margin, near capacity, multi-crane, or over occupied space, needing added planning
Critical load: The IT load the facility exists to protect, the load the power chain must never drop
Critical path: The longest chain of dependent activities; any slip on it moves the finish date [https://anvilfield.com/field-guides/glossary/critical-path/]
Critical root zone: The soil volume a tree depends on for water and nutrients, reaching well past the dripline and shallow in the top 6 to 18 inches [https://anvilfield.com/field-guides/glossary/critical-root-zone/]
Critical zone: The worst-case box driving the reset, the one needing the most static or coldest air at any moment
Critical-environment mindset: The discipline to follow procedure, treat systems as live, and value not making it worse over working fast
Criticality / RCM: Ranking assets by consequence and likelihood of failure; reliability-centered maintenance assigns the strategy per failure mode
CRM: Customer relationship management; the system and practice of keeping the single organized record of every customer and interaction
Cross slope: The slope across the ramp, perpendicular to travel, held to 2 percent (1:48) maximum
Cross-connect: A physical cable joining two circuits patch field to patch field, the manageable interconnection model and the unit the record tracks
Cross-connection: Any path that can let non-potable or contaminated water back into the potable system, including a fill connection [https://anvilfield.com/field-guides/glossary/cross-connection/]
Cross-sectional area: The interior area of the trough, the basis for the 20 percent conductor fill rule [https://anvilfield.com/field-guides/glossary/cross-sectional-area/]
Cross-slope: The tilt across the width of the surface that sheds water, usually given as a percent [https://anvilfield.com/field-guides/glossary/cross-slope/]
Cross-zoned detection: Two independent detection zones that must both confirm before the system releases agent
Crown: The raised centerline and cross-slope that sheds water off the road surface to the ditches [https://anvilfield.com/field-guides/glossary/crown/]
CRRC: Cool Roof Rating Council, which measures and publishes SR, TE, and SRI but does not set thresholds
CSA / SMS / BASICs: The FMCSA enforcement program, its scoring system, and the safety categories that track your USDOT number
CSP: Concrete surface profile, the ICRI roughness scale for a prepared bonding surface, higher numbers rougher [https://anvilfield.com/field-guides/glossary/csp/]
CSP (concrete surface profile): The ICRI roughness scale, CSP 1 smooth to CSP 10 rough, that sets the profile a coating needs to bond
CT (current transformer): A sensor around a conductor that outputs a signal proportional to the current, sized by ratio
CT / PT (VT): Current and potential (voltage) transformers feeding meters and relays [https://anvilfield.com/field-guides/glossary/ct-pt-vt/]
CT ratio: Primary amps to secondary output, such as 100:5 or 200 A to 333 mV, set in the meter to match the CT
CU: Coefficient of utilization, fraction of source lumens reaching the work plane, from the photometric table
CU/AL: The marking on breakers and larger equipment terminals; not a rating for standard aluminum branch devices
Cube / nugget / flake: Hard clear ice for drinks; soft chewable pellets for fast food and healthcare; soft shaved layers for display and medical
Cubic yard: 27 cubic feet; the standard bulk mulch unit; about 13 to 14 two-cubic-foot bags [https://anvilfield.com/field-guides/glossary/cubic-yard/]
Cubic yard (CY): The volume unit for concrete, equal to 27 cubic feet
CUE: Carbon usage effectiveness, carbon per unit of IT energy, in kg CO2e per kWh; carbon factor times PUE [https://anvilfield.com/field-guides/glossary/cue/]
Cues to care: Design signals like a mowed edge or signage that show a native planting is intentional, not neglected
CUI: Corrosion under insulation, the hidden rust of a pipe held wet beneath failed insulation or jacket
Cultural control: Changing mowing, watering, fertility, or variety so site conditions no longer favor the pest
Cumulative sampling: The effect by which many sampling holes pull from the mixed room air at once, the reason ASD works in high airflow
Cupric oxide scale: Black flaky copper-oxide formed inside the pipe when copper is brazed with oxygen present; breaks loose and plugs the system
Curb: Raised frame around the opening that the roof flashing and the hatch tie into
Curb stop and curb box: The utility's shutoff valve at the property line and the access pipe over it operated from the surface with a curb key
Curb-mounted skylight: A skylight set on a raised curb, the standard for low-slope and flat roofs
Curb-to-curb / curb-to-wall: Cover styles for a joint running through the field versus a joint carried up a parapet or a higher wall
Cure and seal: A higher-performance membrane that cures and seals, per ASTM C1315; check flooring compatibility
Cure time: The longer wait, dependent on concrete temperature, before the anchor can carry load
Cure-and-seal: A membrane-forming compound that cures fresh concrete and leaves a sealer film, per ASTM C1315 or C309; a bond breaker for later coatings [https://anvilfield.com/field-guides/glossary/cure-and-seal/]
Cured vs uncured flashing: Cured is the stable vulcanized field rubber; uncured is soft and formable for corners and irregular shapes
Curing: Holding moisture and temperature in set concrete so the cement keeps hydrating and gaining strength
Curing compound: A membrane sprayed after finishing to hold moisture in the set concrete during curing, per ACI 308 [https://anvilfield.com/field-guides/glossary/curing-compound/]
Curling: Edges and corners of a slab lifting off the base from a moisture or temperature gradient top to bottom [https://anvilfield.com/field-guides/glossary/curling/]
Current density: Protective current per unit of bare steel area; set by coating quality and soil resistivity, and the basis for sizing
Current-carrying conductor: A conductor counted for derating, the count that triggers ampacity adjustment when it crosses the threshold
Current-limiting: A device that clears a high fault fast enough to cut peak let-through energy
Current-limiting fuse: A fuse that interrupts within the first half-cycle of a high fault, limiting let-through energy and clearing the arc fast
Curtailment: Cutting the site's grid draw on the grid's worst days, often under a program or interruptible tariff
Curtain wall: A non-structural aluminum-and-glass building skin hung off the structure, carrying only its own weight and wind.
Customer / site / contact: Who is paying, where the work is, and who to reach on site
Customer lifetime value (CLV): The full revenue a customer generates across every job and referral, not just the first ticket
Customer lifetime value (LTV): The total profit a customer produces over the whole time they do business with you, including fees, pull-through, and replacement
Cut and fill: Excavating soil from high areas (cut) and placing it in low areas (fill) to reach the design grade [https://anvilfield.com/field-guides/glossary/cut-and-fill/]
Cut length: The straight sheared stock length, equal to the legs minus the bend deductions
Cut-in / cut-out: The pressures where the switch starts and stops the pump, for example 30/50 psi
Cut-out depth: How far the old mortar is removed, about 2 to 2.5 times the joint width, square back to sound mortar
Cutback asphalt: Asphalt thinned with a petroleum solvent that flashes off; the traditional prime material, now limited by emission rules
Cv: The valve flow coefficient; flow equals Cv times the square root of the pressure drop in psi at a given valve position [https://anvilfield.com/field-guides/glossary/cv/]
CVN: Charpy V-notch impact toughness at a stated temperature, in foot-pounds or joules
Cw: Unit-weight coefficient, 1.0 for normal-weight concrete in the usual density range
CW / HW / HWR: Domestic cold water, hot water, and hot-water return (recirc)
CWI: Certified Welding Inspector, qualified under AWS QC1, who performs the welding inspection
Cx / CxA: Commissioning, and the commissioning authority or agent who plans, witnesses, and signs off the process, independent of the installer [https://anvilfield.com/field-guides/glossary/cx-cxa/]
Cycle and soak: Splitting a run into shorter cycles with soak breaks so water infiltrates instead of running off
Cycle life: The number of open-close cycles a spring is rated for before replacement; high-cycle springs last longer
Cycle rate: How often the stat lets the equipment switch on per hour, set to the equipment type
Cycle-and-soak: Splitting a run time into shorter cycles with soak breaks so water infiltrates instead of running off
Cycles of concentration: The ratio of dissolved solids in the boiler water to those in the makeup water, controlled by blowdown [https://anvilfield.com/field-guides/glossary/cycles-of-concentration/]
Cyclonic pre-separator: A spinning chamber that drops the heavy dust out before the filter so the filter lasts and the airflow holds
D: Jacketed outside diameter of the cable from the manufacturer cut sheet, not the conductor gauge
D1, D2, D3: Thickness in inches of the surface, base, and subbase layers
DAC: Direct-attach copper, a short fixed-length cable with transceivers attached, common in high-density racks [https://anvilfield.com/field-guides/glossary/dac/]
DAC / AOC: Direct-attach copper (short, cheap, low power) and active optical cable (farther, fixed-end optics on fiber)
Daily huddle: A short start-of-shift stand-up that aligns crews on the plan, manpower by area, hazards, permits, and blockers
Daily report / daily log: The contemporaneous record of who was on site, what they did, the conditions, and the problems on a given day
DALI / DALI-2: Digital addressable lighting interface, IEC 62386, with per-fixture addressing and two-way feedback
DALT: Duct air leakage test, the pressurize-and-measure procedure this guide describes
Damp-pack / dry-pack: A stiff grout mixed near-dry and hand-packed where a fluid pour will not work
Dampproofing: A treatment that resists moisture with no hydrostatic pressure, typically a thin coating
Dark fiber vs leased wave: Dark fiber is unlit glass you light and run yourself; a leased wave is a lit channel a carrier runs for you under an SLA
DAS: Distributed antenna system, the antennas and cabling that spread a signal through a building
Dash number: Amp rating of the device, commonly 15, 20, 30, 50, or 60
Data center continuous rating: Manufacturer rating for the heavier data center duty, between prime and standby
Data center operations: The day-2 discipline of running a commissioned facility 24/7: monitoring, rounds, procedures, alarm response, and incident handling that deliver the designed uptime.
Data date: The line in a schedule update dividing actual progress from remaining forecast
Data hygiene: Keeping the data accurate: correct tag-to-asset mapping, calibrated sensors, and live devices, so decisions are sound [https://anvilfield.com/field-guides/glossary/data-hygiene/]
Data sanitization: Removing data from a drive so it cannot be recovered, by clear, purge, or destroy under NIST 800-88
Date of loss: The date the storm occurred, verified by weather data, not the date the damage was discovered
Datum temperature: The temperature below which Nurse-Saul assumes no maturity gain, often near 0 C
Day tank: The small tank near the engine, commonly about an hour of full-load fuel, that feeds the injectors directly
Daylight: An outlet where the pipe discharges at the surface by gravity at a lower point on grade [https://anvilfield.com/field-guides/glossary/daylight/]
Daylight harvesting: Photosensor dimming of daylit-zone fixtures, open-loop or closed-loop, set above the design level
Daylight opening / bite: The visible glass between the stops, and the amount the frame or stop laps over and holds the glass edge
Days payable outstanding: The average number of days you take to pay suppliers, a measure of how you use your terms
Days to invoice (time to invoice): Elapsed time from job completion to the bill being sent
db: Decibel, the unit of insertion loss; a fiber link passes Tier 1 when its measured loss is within the budget [https://anvilfield.com/field-guides/glossary/db/]
dB/km: Fiber attenuation per kilometer, higher at shorter wavelengths [https://anvilfield.com/field-guides/glossary/db-km/]
dBA: A-weighted decibels, sound level weighted to how the human ear responds to frequency [https://anvilfield.com/field-guides/glossary/dba/]
dBA / dBC: A-weighted decibel for most limits; C-weighted decibel to capture low-frequency noise dBA misses
dBC: C-weighted decibel, flatter at low frequency, used to catch the deep hum dBA misses
DBH: Diameter at breast height, trunk diameter at about 4.5 ft up, used for permit thresholds
DC / DCVA: Double check valve assembly, two checks in series for low-hazard protection (ASSE 1015) [https://anvilfield.com/field-guides/glossary/dc-dcva/]
DC / DCVA / DCA: Double check valve assembly; two checks, no relief, for low hazard and both mechanisms (ASSE 1015)
DC arc flash: An arc on a DC system; with no zero crossing it does not self-extinguish, so it is harder to interrupt and carries higher continuous energy
DC fast charging / Level 3: High-power DC delivered straight to the battery; the station, not the car, converts AC to DC
DCDA / RPDA: Double check and reduced pressure detector assemblies; fire-line versions with a metered bypass (ASSE 1048 / 1047)
DCI: Data center interconnect, the transport that carries traffic between data centers across campus, metro, or long-haul distance
DCiE: Data Center Infrastructure Efficiency, the inverse of PUE expressed as a percentage
DCIM: Data center infrastructure management, the database where the floor plan, elevations, and port connectivity live, keyed by the TIA-606 identifiers [https://anvilfield.com/field-guides/glossary/dcim/]
DCIM / CMDB: Data center infrastructure management and the configuration database it reconciles the asset count against
DCKV: Demand-control kitchen ventilation, varying exhaust and makeup with the cooking load
DCV: Demand-control ventilation, modulating outside air to actual occupancy, commonly using CO2 as the occupancy proxy [https://anvilfield.com/field-guides/glossary/dcv/]
DDM / DOM: Digital diagnostic monitoring in an optical module, reporting Tx and Rx power, laser bias, temperature, and voltage for failure prediction
De-energized tap changer: Primary winding taps adjusting the ratio in steps, moved only with the transformer off
De-icing: Treating ice or pack that has already formed to melt it and break its bond to the pavement
Dead band: The temperature range between heating and cooling where the box holds minimum airflow and the reheat valve is shut
Dead bus: A de-energized bus the first set closes to without synchronizing, under first-start arbitration
Dead leg: An uncirculated branch the loop does not reach; the source of tap wait time and stagnation [https://anvilfield.com/field-guides/glossary/dead-leg/]
Dead load: The static weight of the array plus ballast on the structure, in pounds per square foot
Dead load (psf): The permanent weight the array adds to the roof, in pounds per square foot
Dead zone: Distance after a reflection where the OTDR cannot detect or measure the next event
Dead-bus close: The first set energizing an unpowered bus without synchronizing, governed by first-on logic so only one set does it
Deadfront: The cover that exposes only the breaker handles and keeps live parts out of reach
Deadheading: Removing spent flowers so the plant keeps blooming instead of setting seed and slowing down
Deadman: A separate mass of concrete that anchors a brace base when the floor slab alone cannot take the brace load
Deadman / earth anchor: A buried or screw-in anchor that holds a guy line in the ground
Deaerator: A device that strips dissolved oxygen and carbon dioxide from steam-boiler feedwater with heat
Dealer fee / dealer discount: The percentage the lender keeps from what it funds to you in exchange for the promotional plan
Debarment: Removal from eligibility to bid covered public contracts for a period, a top consequence of serious violations
Decay test: Isolating the pump and watching the micron gauge for a rise; proves the vacuum holds, not just that it was reached [https://anvilfield.com/field-guides/glossary/decay-test/]
Dechlorination: Reducing the chlorine in the flush water to a permitted level before discharge, per AWWA C655
Decisions log: The record of what was decided, by whom, when, and on what basis, separate from open actions
Deck (substrate): The structural surface that spans the framing and that the roof system attaches to
Deck ledger: The board that fastens the deck to the house band joist; must be bolted or lag-screwed and flashed, never nailed alone
Deck overlay (LMC / polyester): A bonded wearing course added to extend deck life: latex-modified, polyester polymer, silica-fume, or membrane and asphalt
Deck-level (source-capture) exhaust: Exhaust drawn from low at the water and deck, where the heavy chloramine layer sits, instead of from the ceiling
Deck-mounted / self-flashing: A skylight mounted low to the deck on an integral flashing flange, common on shingled slopes
Deck-mounted post: A pergola post tied into deck framing, not the decking boards, on a deck designed for the added load and uplift
Decompaction: Loosening compacted soil by forking, broadforking, ripping, or subsoiling to restore pore space
Deconstruction: Taking a building apart by hand in reverse of construction to salvage materials for reuse.
Decoupler / common pipe: The short pipe joining primary and secondary loops; it runs backward into deficit under low delta-T [https://anvilfield.com/field-guides/glossary/decoupler-common-pipe/]
DECS: Datacom equipment cooling system, the OCP term for the fluid, heat exchangers, circulation, and controls within the tank or rack
Dedicated equipment space: The reserved volume above the gear footprint, kept free of foreign piping and duct, per 110.26(E)
Dedicated exhaust: A corrosion-resistant, exhaust-only duct system that serves the hoods and never mixes with or recirculates to the building comfort air
Dedicated return: A separate return pipe from the end of the supply back to the heater
Deduct value: The points a distress subtracts from 100, read from ASTM D6433 curves by type, severity, and density
Deductible: The homeowner's share of the loss, owed every claim; it cannot legally be waived, eaten, or rebated
Deep fill: A pour past the neat maximum, extended with specified aggregate or built in lifts
Deep foundation: Piles or drilled piers carrying load through weak soil to a firm layer
Deep soil mixing (DSM): Augering binder into the soil in place to make soil-cement columns or cutoff walls
Deep underdrain / interceptor drain: Deeper or uphill-side drain that lowers the water table or catches lateral seepage before the section
Deep well: A drilled, screened well with its own submersible pump for deep drawdown and high flow in permeable soil
Deep-cycle / AGM battery: A battery built to discharge deeply and recharge repeatedly, unlike a car starting battery
Deep-root fertilization: Injecting a nutrient solution under pressure into the root zone below the surface, a delivery method still governed by the soil test
Deep-seal trap: A trap with a seal deeper than the standard range, used to resist siphonage on hard-to-vent fixtures
Deer-resistant: A plant deer tend to avoid by smell, texture, or chemistry; relative and local, not deer-proof, and it fails under high pressure
DEF: Delayed ettringite formation, internal expansion and cracking from the core running too hot when young, commonly capped at 158F (70C)
Defense in depth: Independent security controls layered in concentric rings so defeating one does not reach the asset
Defensible space: The fire-resistant zone around a structure; the first 5 ft should be noncombustible
Defensive driving: Operating to avoid crashes others may cause, through following distance, scanning, speed control, and leaving an out
Deferred interest / same-as-cash: No interest if the balance is paid in full inside the window; retroactive interest if it is not
Deferred maintenance: Scheduled maintenance not completed on time; a latent risk that grows until corrected
Deferred revenue: Prepaid fees for service not yet delivered, recorded as a liability and recognized as revenue as the visits are performed
Deficiency / issues log: The tracked list of every finding from identify through verify and close, the program's most important operational artifact
Deflagration: A fast flame front through accumulated off-gas that builds pressure and can damage the enclosure [https://anvilfield.com/field-guides/glossary/deflagration/]
Deflection: How far a floor bends under load, limited by a span ratio such as L/360, a serviceability check separate from strength [https://anvilfield.com/field-guides/glossary/deflection/]
Deflection force: The force to deflect the belt span 1/64 in per inch of span, checked against the maker's range
Defrost: Cycle that reverses to cooling to melt frost off the outdoor coil, with aux heat covering the room
Defrost (off-cycle / electric / hot-gas): Periodic melting of coil frost: off-cycle for medium temp, electric heaters or hot discharge gas for low temp, ended on coil temperature with a time fail-safe
Degauss: A magnetic-media method that erases by demagnetizing; it does nothing to solid-state drives
Degree of hazard: Whether backflow would threaten health (high hazard) or only quality such as taste and odor (low hazard) [https://anvilfield.com/field-guides/glossary/degree-of-hazard/]
Delamination: Concrete debonded from the steel over a corroding bar; sounds hollow under chain drag or hammer before it spalls [https://anvilfield.com/field-guides/glossary/delamination/]
Delay: Lost or impacted time, claimable largely when recorded the day it occurs with cause, duration, and impact
Delay skew: The spread in propagation delay between the four pairs, a cable property
Delegated design: A system designed by a licensed professional the contractor hires, submitted under that engineer's stamp
Delta: A closed-loop connection of three windings; line voltage equals phase voltage, line current is 1.732 times phase current
Delta-T: The temperature rise across the unit coil; a strong, stable delta-T means the unit is drawing genuinely hot return air [https://anvilfield.com/field-guides/glossary/delta-t/]
Deluge system: Open heads on dry pipe; detection trips the deluge valve and every head flows at once; for high-hazard areas
Demand charge: A bill component based on the highest demand in the period, not on total energy used [https://anvilfield.com/field-guides/glossary/demand-charge/]
Demand defrost: Control that initiates defrost from coil sensor readings only when frost has actually built up
Demand factor: The fraction of a connected load counted toward the service, set by the Article 220 tables
Demand load: The diversified load after Article 220 demand factors, what the feeder really carries [https://anvilfield.com/field-guides/glossary/demand-load/]
Demand response: Curtailing or shifting load on a utility signal so the site supports the grid at a peak
Demand response (DR): Reducing grid draw when the utility or ISO calls an event, in exchange for a payment or a lower rate
Demand-controlled recirculation: A control that runs the pump only when a fixture calls for hot water
Demand-controlled ventilation: Modulating airflow to a measured contaminant, such as garage CO and NO2 or room CO2
Demand-controlled ventilation (DCV): Controlling outdoor air to measured CO2 or occupancy, adding fresh air when CO2 rises and cutting it when a space empties
Demand-critical weld: A weld the seismic system relies on to yield without fracture, under AWS D1.8 and AISC 341
Demarc: Demarcation point, the specific port where one party's ownership ends and the next party's begins
Demolition robot: A remote-controlled tracked machine with a breaker, shear, or bucket that lets the operator work a dangerous or unstable structure from a safe distance
Dense-graded aggregate (DGA): A well-graded crushed blend from top size down to fines that compacts tight; also crusher run, 21A, 411, GAB
Dense-graded aggregate base: Crushed stone blended down to fines that locks tight when compacted; the layer that carries the load
Dense-graded HMA: Well-graded mix that packs tight and seals; the standard for most layers
Densifier: A lithium, sodium, or potassium silicate that reacts with free lime to harden and dust-proof the surface
Density: Mass per unit volume of applied SFRM, verified to ASTM E605 against the listed minimum [https://anvilfield.com/field-guides/glossary/density/]
Density (lb/ft3): Cured foam weight per cubic foot, 2.5 to 3 for roofing foam, confirmed by cores
Density differential: How far the joint density falls below the adjoining mat density, commonly limited to about 2 percent [https://anvilfield.com/field-guides/glossary/density-differential/]
Depth: Mulch or soil thickness, in feet for the /27 form or inches for the /324 form
Derate: The percent of nameplate kW lost to site elevation and high ambient temperature
Descaling: Circulating acid through a tankless heat exchanger to remove mineral scale
Descending interface: The boundary between the agent-rich layer and infiltrating air that sinks as the room leaks, used to model retention
Desiccant: The moisture-adsorbing material inside a drier, commonly molecular sieve plus activated alumina
Design / derated load: A planned fraction of nameplate, commonly 50 to 75 percent, used to size systems
Design / working pressure: The pressure the system is rated and designed to operate at; the basis for the test pressure
Design concentration: The agent percentage by volume the room is flooded to, the minimum extinguishing concentration times a safety factor
Design conditions: The 1 percent cooling and 99 percent heating outdoor values from ASHRAE
Design delta-T: The supply-to-return difference the plant was sized for, e.g. 44 F supply and 56 F return is a 12 F rise
Design density and area: The water rate in gpm per square foot applied over the most remote design area; the basis the calculation must meet
Design ESALs: Total equivalent single axle loads expected over the design life, the traffic number the section is sized to
Design letter: NEMA A through D, the torque-and-slip class of the motor
Design rainfall rate: The 100-year rainfall in inches per hour for the site, from the code map or NOAA Atlas 14 [https://anvilfield.com/field-guides/glossary/design-rainfall-rate/]
Design slope: The pitch built into the roof toward drainage, commonly 1/4 in per ft minimum for membrane roofs
Designated area: A location built and maintained as safe for hot work, such as a noncombustible shop bay, where routine hot work can be permit-free [https://anvilfield.com/field-guides/glossary/designated-area/]
Destratification: Mixing the warm ceiling air back down to the floor with high fans to cut the vertical temperature spread
Desuperheater: An auxiliary heat exchanger that captures compressor discharge heat to warm domestic hot water
DETC / LTC: De-energized tap changer, moved only dead, versus a load tap changer designed to move energized
Detect / recognize / identify: The three goal levels: detect a presence (about 20 to 25 ppf), recognize a known person (about 40 to 50), identify a stranger (80 or more)
Detect vs isolate: Detection finds and locates the leak; isolation stops it by closing a valve. Both are required, not just the first
Detectable warning: Truncated-dome panel at a curb ramp warning of the edge between walk and vehicular way [https://anvilfield.com/field-guides/glossary/detectable-warning/]
Detention: Holding stormwater temporarily and releasing it slowly so the peak rate out is no higher than pre-development; the basin empties between storms [https://anvilfield.com/field-guides/glossary/detention/]
Detention volume: The water the roof must store during the design storm to stay under the release rate
Deterioration curve: The accelerating drop in pavement condition over time, flat at the top and steep at the bottom, that sets treatment timing [https://anvilfield.com/field-guides/glossary/deterioration-curve/]
Dethatching (power raking, verticutting): Mechanically tearing out excess thatch with spring tines, flails, or vertical blades
Detuned reactor: Series reactor that shifts the bank's resonance below the lowest harmonic so it cannot ring
Developed length: The measured pipe run along its actual path plus the equivalent length of fittings, not the straight-line distance [https://anvilfield.com/field-guides/glossary/developed-length/]
Development length (ld): The embedment a bar needs to develop its strength, varying with bar, grade, f'c, cover, and position [https://anvilfield.com/field-guides/glossary/development-length-ld/]
Dew point: The temperature at which moisture condenses out of the air; the coil supply water is held above it to keep the coil dry [https://anvilfield.com/field-guides/glossary/dew-point/]
Dew point / flash rust: The temperature at which moisture condenses; flash rust is the instant rust bloom on bare steel below the spread
Dew point margin: The gap between the chilled water supply temperature and the room dew point, commonly held to at least about 2°F
Dewatering: Controlled lowering and removal of groundwater so an excavation can be worked dry below the water table
Dewpoint: The temperature at which air becomes saturated and water condenses, the true measure of how dry the air is
DFT: Dry film thickness in mils, the cured coating depth the warranty is written to
DFU: Drainage fixture unit, a dimensionless load value for a fixture used to size drains and vents; one DFU is about 7.5 gallons per minute of discharge [https://anvilfield.com/field-guides/glossary/dfu/]
DGA: Dissolved gas analysis, identifying internal faults from gases dissolved in transformer oil [https://anvilfield.com/field-guides/glossary/dga/]
DI / deionization: Ion-exchange polishing that trades dissolved ions for hydrogen and hydroxide on resin
DI water: Deionized water, the low-ion makeup and dilution water the fluid is formulated for, far cleaner than tap or softened water
Diagnostic fee: The charge to come out and find the fault, commonly credited to the repair if the customer proceeds
Diaphragm: The roof or floor that ties the panels together as the permanent lateral system, letting the braces come off
Diaphragm / bladder tank: The modern tank with a membrane separating a pre-charged air cushion from the system water
Diaphragm kit: The rubber diaphragm, relief valve, and bypass that meter a diaphragm flushometer and set its flush volume.
Diaphragm tank: An expansion tank with a fixed membrane separating the air charge from the system water
Dieback: Progressive death of branch tips and limbs from the top down, a sign of a tree losing the establishment fight
Dielectric: The electrical property of the concrete that sets the pulse velocity; roughly 6 to 8 in dry concrete, higher when wet
Dielectric absorption ratio (DAR): Ratio of the 60-second to the 30-second reading, the quick version of PI
Dielectric coolant: Non-conductive cooling fluid that a conductivity-based water sensor cannot detect, requiring a fluid-matched sensor
Dielectric fitting: An insulating union or nipple that stops galvanic corrosion where copper meets steel [https://anvilfield.com/field-guides/glossary/dielectric-fitting/]
Dielectric fluid: The non-conductive liquid the hardware is submerged in; it carries heat off the components by direct contact [https://anvilfield.com/field-guides/glossary/dielectric-fluid/]
Dielectric strength: A fluid's ability to resist conducting electricity; it must stay high and drops with contamination or water
Dielectric vs conductive coolant: Dielectric fluid does not conduct; water and treated glycol do, so a conductive leak on a live board can short it
Difference voltage: The volts added or subtracted, the only part the windings actually handle
Differential (87): Zone protection that compares current in against current out and trips fast for an internal fault without a coordination delay
Differential (thermal gradient): The temperature difference between the core and the surface, commonly limited to 35F (19.4C)
Differential / swing: The temperature gap between switching on and off, wider on line-voltage stats
Differential gauge: The test instrument that reads pressure across one part at a time through high, low, and bleed needle valves
Differential pressure: The static pressure drop across the coil; the rise over a clean baseline at the same airflow is the cleaning trigger
Differential pressure (dP): The pressure difference the CDU holds across the manifold headers to keep each rack branch fed
Differential relaying: Protection that trips on the difference between current entering and leaving a zone; fast and selective on its own zone
Differential settlement: One part of a foundation settling more than another, the movement that cracks and racks a structure
Differing site conditions: Physical conditions that materially differ from what the contract documents represented
Diffuser: The top and bottom manifolds that spread flow to a low velocity to preserve stratification
Diffusion vs air leakage: Diffusion is slow vapor movement through solid material; air leakage is bulk air through gaps, carrying far more water
Digital twin: The maintained as-built model the operations team runs the building from, often tied to DCIM in a data center [https://anvilfield.com/field-guides/glossary/digital-twin/]
Direct cost: Labor, material, equipment, and subs that tie to one job, before overhead
Direct evaporative (DEC): Wets the supply air itself; cools and humidifies the space (the swamp cooler)
Direct-burial cable: Two-conductor stranded-copper low-voltage cable jacketed for soil contact without conduit
Direct-drive: Motor coupled straight to the fan wheel, no belts or sheaves
Direct-fired: Burner fires into the airstream; high efficiency, combustion products in the supply
Direct-to-chip / cold plate: A cold plate on the CPU or GPU with coolant flowing through it to take heat at the source
Directional troweling / back-butter: Combing ridges in one direction and sliding the tile across them to collapse voids; back-buttering adds a skim of mortar to the tile back for large or warped tile.
Discharge means: Bleed resistor or device that drains the capacitor's residual voltage after disconnection
Disconnecting means: The NEC term for the device that disconnects a circuit from its supply; a switch, breaker, or in some cases a plug [https://anvilfield.com/field-guides/glossary/disconnecting-means/]
Disinfection: Chlorinating a line to kill the bacteria the install brought in, then proving it clean before service
Disinfection CT: Disinfectant residual concentration (mg/L) multiplied by contact time (minutes); the measure of how much disinfection the water received
Dispatch: Assigning a scheduled work order to a specific tech and time
Dispatching vs scheduling: Scheduling places a job on a future day and window; dispatching assigns it to a tech and sequences it on the day
Displacement PF: Power factor from the phase shift between voltage and current, the part capacitors correct
Displacement pile: A pile that pushes soil aside as it drives, rather than removing it like a drilled shaft
Displacement vs distortion PF: Displacement is the phase shift caps correct; distortion is from harmonics and they cannot
Disposition: The decision on nonconforming work: rework, repair, use-as-is, or reject, with engineering dispositions set by the engineer [https://anvilfield.com/field-guides/glossary/disposition/]
DISS: Diameter index safety system, one gas-specific non-interchangeable connection scheme for outlets
Dissipating-resin compound: A curing compound meant to break down over weeks so flooring can bond; confirm with the flooring maker
Distracted driving: Operating while attention is on something other than driving, most dangerously a phone, by hand or by mind
Distress: A defect recorded in the survey, named from the standard's catalog: alligator cracking, rutting, raveling, and so on
Distribution box (D-box): Buried box that splits effluent evenly among the drainfield trenches; must be and stay level
Distribution unit: A manifold that splits one primer's metered water evenly among several floor-drain traps, commonly up to four
District heating: A network distributing heat to many buildings through insulated pipe, the largest-scale outlet for recovered heat
Disturbing frequency: The frequency of the force the equipment makes, set mainly by running speed
Diverse path: A physically separate route, conduit, and building entrance from the working path, so a single fiber cut cannot isolate the site
Diversity: The statistical fact that not all fixtures draw at once, which the demand curve builds in [https://anvilfield.com/field-guides/glossary/diversity/]
Diversity factor: The reduction applied because not every inlet draws vacuum at the same moment
Divider strip: A zinc, brass, aluminum, or plastic strip set on edge that controls cracking, makes the pattern, and handles joint movement
DJE: Direct job expenses: permits, rental, temp power, consumables, testing, and travel for the job
DLC / direct-to-chip: Direct liquid cooling, coolant through cold plates clamped to the CPUs and GPUs
DLC listing: DesignLights Consortium qualified products list, the gate most utility rebate programs use
DLRO: Digital low-resistance ohmmeter, used for winding resistance in the milliohm and microhm range
DM: Distance multiplier, for the vertical travel of the load
DMM: Digital multimeter, reading voltage, resistance, and continuity, and usually current
DOAS: Dedicated outdoor air system, a unit that conditions only the ventilation outdoor air and handles the latent load [https://anvilfield.com/field-guides/glossary/doas/]
Dock leveler: A hinged steel plate in a pit or on the dock face that bridges the gap and height difference to the trailer bed
Dock seal / shelter: Foam pads or a fabric enclosure that close the weather gap between the trailer and the building
Document control: The practice of keeping everyone building from the current, correct documents and tracking how those documents change
DOI (distinctness of image): How sharply the surface reflects an image, read with a clarity meter alongside gloss and haze
DOL / across-the-line: Direct-on-line, full-voltage starting through a contactor with no voltage reduction
Donor antenna: The antenna or feed that captures the outside signal the system rebroadcasts, off-air from a tower or fed by the carrier
Door balance: Spring tension matched to door weight so a disconnected door floats and holds position anywhere in its travel
Door fan / room integrity test: A pressurization test that measures enclosure leakage and predicts how long the room will hold the agent
Door operator: The motor and linkage that opens and closes the doors. The number one source of callbacks, so the highest-return item in most mods
Dormancy: Brown but living turf in cold or heat that greens back when the season turns [https://anvilfield.com/field-guides/glossary/dormancy/]
Dormant vs active crack: A crack that has stopped moving versus one still opening and closing, which decides rigid versus flexible
Dosage: Fiber added per volume of concrete, in pounds per cubic yard or kilograms per cubic meter
Dosimeter: A worker-worn meter that integrates noise over the shift into a personal dose and TWA
Double interlock: Pre-action that admits water only when both detection operates and the sprinkler piping loses air; the data center default
Double riser: Parallel small and large risers with a trap, used on unloading systems to hold velocity across loads
Double suction riser: Two parallel risers with a base trap, so oil returns at part load through the small riser and pressure drop stays in budget at full load
Double-conversion online / VFI: Load always on the inverter, zero transfer, full isolation from the utility
Double-tee: A floor or roof member, two stems under a flange, spanning long and laid side by side
Dowel: A smooth steel bar transferring shear across a joint so a curled edge stays carried under load [https://anvilfield.com/field-guides/glossary/dowel/]
Dowel bar: Smooth round bar across a transverse joint that transfers load and slides on one debonded end
Down conductor: A conductor carrying strike current from the roof network to the grounding electrodes, minimum two per structure
Downfeed: Distribution that lifts water to a high tank and feeds down by gravity
Downspout / leader / conductor: The vertical pipe carrying water from the gutter down and away
Downstream injector: A device that draws the cleaning solution into the stream after the pump, at low pressure, for soft washing
dP: Differential pressure across the containment barrier, the primary number that proves the seal holds [https://anvilfield.com/field-guides/glossary/dp/]
DP setpoint: The differential pressure the variable-speed pumps hold, ideally sensed at the far load
DQ file: Driver qualification file, the records proving a driver is legally qualified, commonly under 49 CFR 391.51
DRaaS: Disaster recovery as a service, the recovery environment and failover hosted by a provider
Draft: The pressure that moves combustion products out through the flue, measured in inches of water column
Draft hood: The appliance-matched fitting on an atmospheric heater that dilutes exhaust and relieves downdrafts
Drain air gap: A clear vertical space between the drain outlet and the receiver flood rim, with no direct connection, required by plumbing code
Draindown: Binder running off the stone in an open-graded asphalt mix when it runs too hot or is held too long
Drained area: The horizontal roof projection feeding a gutter, in square feet, plus any wall that drains onto it
Drainfield / leach field: The bed of trenches in native soil where effluent is dispersed and the soil treats it; also called the soil absorption field
Draw-through: Fan downstream of the coil, so the pan runs at negative pressure and a condensate trap is mandatory
Draw-through / blow-through: Fan downstream of the coil (negative pan pressure) versus upstream of it (positive), which sets the trap [https://anvilfield.com/field-guides/glossary/draw-through-blow-through/]
Drawdown: The drop from static to pumping level; also the gallons a tank delivers between cut-out and cut-in [https://anvilfield.com/field-guides/glossary/drawdown/]
Drawdown / yield: How far the water level falls under pumping, and the sustainable rate in gpm the well delivers
Drawdown time: How long the reservoir takes to empty after a storm, set by the design to be ready for the next one
Drawout: A breaker that racks in and out of the gear without disturbing the bus connections
Drawout / racking: The mechanism that moves a breaker between connected, test, and disconnected positions in its cell
Drift: Fine liquid droplets carried out of the tower by the airflow, limited by drift eliminators [https://anvilfield.com/field-guides/glossary/drift/]
Drift load: The extra snow surcharge piled by wind at parapets, valleys, and roof steps, often several times the balanced load
Drilled pier / drilled shaft / caisson / bored pile: All names for a large-diameter cast-in-place concrete shaft drilled to a firm bearing layer and reinforced with a steel cage
Drip edge: Perimeter metal at eaves and rakes that kicks water off the edge and ties the roof down against wind [https://anvilfield.com/field-guides/glossary/drip-edge/]
Drip hem: The bottom edge of the fascia or coping bent back into a hook that locks over the continuous cleat
Drip leg: A pocket at a low point that collects condensate so a trap can drain it before it pools in the main
Drip leg / drop leg: A vertical dead-end below the main with a drain to catch condensate
Drip line: The ground circle under the outer edge of the canopy, a target for the mulch ring
Drip tray / containment: A pan that catches escaped coolant and drains it to a safe point, the physical defense before the sensor fires
Dripline / emitter tubing: Poly tube with emitters molded in at a set spacing, laid as a line or grid through beds and turf
Drive aisle: The lane cars travel and back into; commonly 24 ft for two-way 90-degree parking
Driven pile: A steel, concrete, or timber member hammered into the soil to carry load, displacing soil as it goes
Driven sheave: The sheave on the fan shaft, usually a fixed sheave
Driven vs helical piling: Driven pilings are hammered into the bottom; helical pilings are screwed in until torque proves capacity
Driver sheave: The sheave on the motor shaft, sometimes the adjustable variable-pitch one
Drone / UAV inspection: Using a remotely piloted unmanned aircraft system to inspect assets that are dangerous, slow, or costly to reach, leaving a visual and thermal record.
Droop: The amount a valve's downstream pressure sags below setpoint as load rises, worst on direct-acting valves [https://anvilfield.com/field-guides/glossary/droop/]
Drop: One horizontal cable run from a patch panel position to a device port, the unit the copper takeoff counts
Drop zone: The cleared area below where the tree or its cut pieces are landed
Drop-on beads: Glass beads scattered onto the wet marking for immediate surface reflectivity
Drop-on vs intermix beads: Drop-on beads are broadcast onto the wet line for night-one return; intermix beads are blended in to surface as the line wears
Drought-tolerant: A plant that lives on low water once established; not no-water, and not low-water before its roots grow in
DRUPS: Diesel rotary UPS, riding through on a spinning mass coupled to a diesel engine
Dry bulb: Plain air temperature, what a standard thermometer reads, blind to moisture
Dry cleaning: Removing loose soot with chemical sponges and HEPA vacuuming before any liquid is used
Dry film thickness (DFT): The cured coating thickness in mils, held within the data sheet range and measured per SSPC-PA 2
Dry pipe system: Pipe held under air or nitrogen; a dry-pipe valve trips and water follows when a head opens; used in freeze-prone space
Dry smoke: Powdery residue from a fast, hot fire in natural materials, which lifts with dry methods
Dry soot: Powdery residue from a fast, hot fire; dry-cleaned with a HEPA vacuum and dry sponge, never wetted first
Dry standard: The moisture content of the same material in an unaffected area, the documented target you dry back to [https://anvilfield.com/field-guides/glossary/dry-standard/]
Dry trap: A trap whose seal has evaporated or been siphoned away, leaving an open path for sewer gas
Dry vent: A vent pipe that carries only air and never drainage; every wet-vented group still needs one [https://anvilfield.com/field-guides/glossary/dry-vent/]
Dry, cased, and slurry methods: The three ways to hold the hole open: an open hole in stable ground, a steel casing, or a fluid that holds the wall by pressure
Dry-bulb: Air temperature read by a standard thermometer, before any evaporation
Dry-bulb / wet-bulb / enthalpy: The outdoor measurements that trigger changeover; enthalpy includes humidity, wet-bulb drives evaporative systems
Dry-bulb temperature: The temperature an ordinary thermometer reads, the sensible temperature of the air, plotted on the horizontal axis [https://anvilfield.com/field-guides/glossary/dry-bulb-temperature/]
Dry-bulb vs enthalpy: Changeover on temperature alone, or on total heat content to include humidity
Dry-firing: Firing a boiler with insufficient water, overheating the unwetted metal and cracking or collapsing the pressure vessel
Dry-in: Getting the deck weather-tight with underlayment before the roof covering is installed
Dry-in / night seal: Making opened work temporarily watertight at the end of a shift
Dry-pack: A stiff near-zero-slump grout rammed into place where flow under the plate is not possible
Dry-pipe system: Sprinkler system holding pressurized air in the pipe, with water released by the dry-pipe valve when a sprinkler fuses and the air bleeds off
Dry-shake color hardener: Pigment, sand, and cement broadcast on the fresh surface and floated in for surface color and a harder wear surface
Dry-type: Transformer cooled by air and solid insulation, with no liquid
Drying shrinkage: The volume loss as concrete dries, driven by water content and paste, that the curl is built from [https://anvilfield.com/field-guides/glossary/drying-shrinkage/]
ds, dh: Static and hydraulic head in inches, set by the overflow inlet height and its design flow
DSO (days sales outstanding): Average days to collect after billing; receivables divided by credit sales, times days in the period
DTC / D2C / cold-plate: Direct-to-chip liquid cooling, a cold plate on the chip with coolant flowing through it
DTI: Direct-tension-indicator washer, ASTM F959, whose bumps crush as the bolt tensions
DTM: Digital terrain model, the three-dimensional design surface a 3D machine is driven to
DU / DULQ: Distribution uniformity, and its lower-quarter form, the dry quarter average over the overall average
Dual maximum: A reheat sequence with separate cooling and heating maximum airflows, allowing a low cooling minimum
Dual plumbing: A building plumbed with both potable and reclaimed systems run separately
Dual-cord A/B power: Two independent power feeds to one device, one cord each, from separate sources for redundancy
Dual-function breaker: One breaker providing both AFCI and GFCI protection, common on kitchen and laundry circuits
Duct bank: A grid of conduits run underground and encased on all sides in concrete to protect and route multiple feeders
Duct liner: Fibrous insulation bonded inside the duct for sound absorption and insulation, in the airstream
Ductboard: Rigid duct cut from resin-bonded fiberglass board with a foil facing
Ductor: A low-resistance ohmmeter that reads the micro-ohm contact resistance across a bolted joint
Ductor / low-resistance ohmmeter: An instrument that measures a bolted connection in micro-ohms to find a high-resistance joint that torque alone cannot reveal
Ductulator: A slide-wheel or app version of the friction chart that converts CFM and friction rate into a duct size and velocity
Due diligence: The confirmation studies, power, geotech, environmental, and title, that verify a shortlisted site before commitment [https://anvilfield.com/field-guides/glossary/due-diligence/]
Dumbbell / centerbulb: PVC profiles: flat dumbbell for static joints, hollow centerbulb for moving joints
Duplex: A device with two receptacles on a single mounting strap, the common wall outlet
Duplex / alternation: Two pumps, each at full design flow, that alternate the lead so they wear evenly; the lag pump joins on high inflow
Dust-holding capacity: How much dust a filter holds before reaching final pressure drop, which sets its life
Dusting: A soft, powdery surface that never hardened, from bleed water finished in or carbonation
Duty point: The design flow in GPM paired with the system head in feet; the point on the pump curve the pump is selected to hit
Duty rating: The scaffold's load class, light, medium, or heavy, tied to a load per square foot from the manufacturer
Duty rating / Type: Maximum rated load in pounds, worker plus tools; ANSI Type IAA 375, IA 300, I 250, II 225, III 200
DVIR: Driver vehicle inspection report, the federally required record of a commercial truck's condition under 49 CFR 396.11 [https://anvilfield.com/field-guides/glossary/dvir/]
DVIR / pre-trip inspection: Driver vehicle inspection report, the walk-around check of brakes, tires, lights, and safety items before a vehicle runs
DWDM: Dense wavelength division multiplexing, many independent channels of light on one fiber, each on its own wavelength on the ITU grid
Dwell time: The minutes a soft-wash solution sits on the surface to kill the growth before rinsing, without being let dry
DWV: Drain, waste, and vent, the gravity piping that carries waste out and lets the system breathe [https://anvilfield.com/field-guides/glossary/dwv/]
DX: Direct expansion, refrigerant cooling made at the unit and rejected to a condenser outside
DX / direct expansion: Cooling where refrigerant evaporates in a coil directly in the airstream, with no water loop in between
DX / evaporator coil: A direct-expansion cooling coil where refrigerant boils inside the tubes to cool the air
DX cooling: Direct-expansion cooling integrated into the enclosure, sized to the IT load it carries
Dynamic / centrifugal: Compression by accelerating vapor with an impeller and converting velocity to pressure
Dynamic cable: Synthetic hollow-braid line wrapped around leaders that allows some controlled movement, non-invasive
Dynamic load: The peak force when a falling rigged piece comes tight on the rope, well above its static weight
Dynamic load test: High-strain testing, PDA with CAPWAP, that measures capacity and stress from the driving blows under ASTM D4945
Dynamic rating: Listing to close against a stated airflow velocity and static pressure with the fan running
E: Evaporation rate, kg per square meter per hour from this equation; convert to lb per square foot per hour for the ACI threshold
E-sign and deposit: The digital signature and money down that lock the scope, the price, and the schedule slot
E-stop / pull-cord: Emergency stop device; a pull-cord runs the length of the conveyor and drops the line when pulled from anywhere along it
E1 / E2 / E3: The 0.3 to 1, 1 to 3, and 3 to 10 micron particle-size groups MERV is scored across
Earn-out: Part of the price paid only if the business hits agreed targets after closing
Earned hours: Installed quantity times the budgeted hours per unit, the credit the estimate gives for work in place; also percent complete times budgeted hours
Earned revenue: Percent complete times the revised contract value; what you have earned regardless of what you billed
Earth gradient: Voltage in the soil around a sheath fault, read with an A-frame to locate it
Earth retention / shoring: An engineered structure that holds back soil for a deep excavation and limits ground movement, distinct from an OSHA trench protective system that protects the worker.
Earthwork / grading: Moving and shaping soil to bring a site to the design elevations and slopes
East-west / north-south: Server-to-server traffic inside the data center versus traffic in and out of the building
EATR: Exhaust air transfer ratio, the percent of exhaust air carried back into the supply stream
Eave vs rake: The eave is the horizontal bottom roof edge; the rake is the sloped gable edge
EBITDA / SDE multiple: Sale price stated as a multiple of normalized earnings; SDE for small owner-run shops, EBITDA for larger firms
EC fan: Electronically commutated fan that modulates speed smoothly, the part that lets in-row turn down and save fan energy [https://anvilfield.com/field-guides/glossary/ec-fan/]
EC motor: Electronically commutated motor with on-board variable-speed control, efficient across turndown
Eccentric reducer: A reducer offset to one side; on a horizontal suction it is installed flat side up so air cannot pocket against the pump [https://anvilfield.com/field-guides/glossary/eccentric-reducer/]
Echelon paving: Two pavers running side by side and staggered, laying adjacent lanes hot against hot for the strongest joint
ECM: Electronically commutated motor that holds a commanded airflow as filter resistance changes [https://anvilfield.com/field-guides/glossary/ecm/]
ECM motor: Electronically commutated; a constant-airflow blower that speeds up to hold CFM as static rises
ECMP: Equal-cost multi-path routing, which hashes flows across parallel paths and can overload one link when large flows collide on the same path
ECN: Explicit congestion notification, an end-to-end mark that tells a sender to slow down before a buffer overflows
Eco mode: High-efficiency mode feeding the load through the bypass path
Eco-mode: High-efficiency mode running the load on bypass with the inverter on standby
Economic life: The point where total cost per hour is lowest, the rational time to replace the machine
Economizer: A control that uses cool or dry outside air for free cooling when conditions allow, cutting compressor run time [https://anvilfield.com/field-guides/glossary/economizer/]
Economizer / free cooling: Using cold outside air or water to cool when conditions allow, idling the compressors
Economizer FDD: Logic that compares an economizer's expected state to its actual state and flags the fault
Ecoregion: An area sharing climate, soils, and vegetation; the EPA Level III and IV units are the common sourcing reference
ECR: Epoxy-coated rebar, the green fusion-bonded barrier coating under ASTM A775/A934
Edge / micro: A small facility placed near the data for low latency, often unstaffed and remotely managed
Edge data center: Compute deployed near where data is created or used, to cut latency and bandwidth and survive a WAN outage
Edge drain / longitudinal underdrain: Perforated pipe in a filter-wrapped aggregate trench along the pavement edge that collects base water
Edge metal: Formed sheet metal capping the roof perimeter: fascia, coping, drip edge, and gravel stop
Edge restraint: The spiked edge or concrete haunch anchored in the base that holds the perimeter from spreading [https://anvilfield.com/field-guides/glossary/edge-restraint/]
Edge seal: Sealing the perimeter joint between patch and pavement to keep water out
EDI: Electrodeionization, continuous DI regenerated by an electric field, no regeneration chemicals
EDM / discharge: Electrical discharge machining; here the arc of shaft current through a bearing that pits the race
EDR: Equivalent direct radiation, square feet, an older rating for radiator and boiler steam output
EER: Energy efficiency ratio: cooling BTU per hour divided by watts drawn at the rated condition
EEV: Electronic expansion valve, the metering device at each indoor unit, the part oxide scale fouls first
EEWP: Energized electrical work permit, required when energized work cannot be avoided
Eff: Thermal efficiency or recovery efficiency as a decimal, from the manufacturer's rating
Effective bearing area: The plate area actually in contact with grout, where load transfers; voids subtract from it
Effective depth (d): The distance from the compression face to the tension steel, what gives the section its strength
Effective ground-fault current path: The intentionally constructed, low-impedance bonded metal route fault current takes back to the source
Effective ground-fault path: The permanent, low-impedance path required by 250.4 that carries fault current back to the source to trip the device
Effectiveness: The ratio of energy actually transferred to the maximum possible, reported as sensible, latent, or total percent
Efficacy (lm/W): Lumens of light produced per watt of power, the measure that drives the energy savings
Effluent filter: Screened cartridge in the tank outlet that catches fine solids before they reach and clog the field; cleaned on a schedule
Effluent oil limit: Maximum oil concentration in the discharge, in mg/L, set by the pretreatment permit
EFVM: Electric field vector mapping, an electronic leak detection method that pinpoints a membrane breach, usable through overburden
EGC: Equipment grounding conductor, the fault path bonding equipment metal back to the source, sized from Table 250.122 by the overcurrent device [https://anvilfield.com/field-guides/glossary/egc/]
EGC (equipment ground): The bare or green-insulated fault path; lands on the green screw
EGC / GEC: Equipment grounding conductor and grounding electrode conductor
Egress: The path and door out of the working space, with two entrances and panic hardware required on large gear
EGT: Exhaust gas temperature, the truer measure of whether a diesel is loaded enough to burn fuel completely
EH / PR / MT: ASTM F2413 footwear add-ons: electrical hazard, puncture resistance, metatarsal protection
EHD: Equivalent hydraulic diameter, how CSST is sized instead of nominal pipe size
EIFS: Exterior insulation and finish system: foam board, base coat, mesh, and a thin synthetic finish
Elastomeric / urethane membrane: A flexible, usually polyurethane, liquid-applied coating that cures to a continuous waterproof film with enough elongation to bridge cracks
Elastomeric coating: Silicone, acrylic, or polyurethane top layer applied in dry mils for UV and weather protection
Elbow (ell): A change of direction, drawn as a bend; the angle (90, 45, eighth bend) is noted or implied by the axes
ELD: Electronic leak detection, locating a membrane breach by the electrical current that flows through it to a grounded conductive substrate
Electric shock drowning (ESD): Drowning caused when AC leakage into the water paralyzes a swimmer's muscles so they cannot swim; the deadly hazard at powered docks
Electric sign: A self-illuminated display fed by building power, generally a UL 48 listed assembly installed under NEC Article 600
Electric stress field: The electric field through the cable insulation between the conductor and the grounded shield, intense enough to need control at any cut end
Electric strike vs maglock: A strike releases a latch and is usually fail-secure with mechanical free egress; a maglock holds by magnet, is fail-safe, and needs separate egress release
Electrically safe work condition (ESWC): A state where a circuit is de-energized, locked and tagged, tested to verify the absence of voltage, and grounded where required
Electronic leak detection (ELD): Locating a membrane breach electrically, including under overburden
Electronic leak detection / EFVM: A method that runs a current to pinpoint a membrane breach to within inches, usable through media and ballast without removing the overburden
Elevator modernization: Planned replacement of an aging car's worn systems, mainly the controller, drive, and door operator, to restore reliability, ride, and code compliance
Elongation: The measured stretch of the strand under load, the independent proof the design force went in
Embed plate: Steel plate cast into a member, anchored by headed studs, that field connections weld or bolt to
Embedment: The portion of the wall buried below finished grade, commonly about 10 percent of exposed height or one course [https://anvilfield.com/field-guides/glossary/embedment/]
Embedment (h-ef): The bonded depth of the rod or bar in the concrete, set by the design from the ESR
Embodied carbon: Emissions in construction and hardware manufacture, in scope 3, separate from operational energy
Emergency board-up: Temporary securing of wall openings with exterior-grade plywood or OSB to keep weather and intruders out after a loss
Emergency floor drain: A floor drain placed for an occasional spill or washdown that gets little regular water and is prone to a dry trap
Emergency spillway: The armored overflow path that safely passes the storm bigger than the outlet can handle, protecting the embankment from overtopping
Emergency system (NEC 700): Backup for code-mandated life-safety loads; the strictest class, with the fast transfer, the wiring independence, and selective coordination
Emergency vs non-emergency: The engine classification that decides the required tier and the run-hour limits
EMI / RFI: Electromagnetic and radio-frequency interference, the electrical noise an isolated ground aims to keep off the ground path
Emissivity: The fraction of energy a surface radiates compared to a perfect emitter, 0 to 1; bare metal is low, painted or oxidized surfaces are high
Emitter / dripper: The device that meters water out of the line at a low, rated flow; point-source or molded inline
EMR: Experience modification rate, a multiplier on workers comp premium from a three-year claims history; 1.0 is average, below 1.0 is better than average [https://anvilfield.com/field-guides/glossary/emr/]
EMR / e-mod: Experience modification rate; a workers' comp multiplier against 1.0 that drives premium and bid prequalification
EMS: Emergency medical services, the 911 ambulance and paramedic response
EMS / EVEMS: Energy management system that limits EVSE load so the feeder and service need not carry full simultaneous demand (625.42) [https://anvilfield.com/field-guides/glossary/ems-evems/]
Emulsion break: The point where the asphalt separates from the water in the emulsion and the surface turns from brown to black before it cures
Encapsulant: A sealing coat applied to a surface that cannot be fully cleaned, locking the remaining odor in
Encapsulated flotation: A closed-cell foam core sealed in a polyethylene shell, which stays buoyant if punctured and does not shed foam; bare foam is restricted
Encapsulation: A coating applied to a cleaned, dried surface after remediation, never a substitute for removal
Encasement: The concrete jacket around the conduit grid, commonly 3 in on all sides, often dyed red for identification
Encircled flux (EF): Defined multimode launch condition, IEC 61280-4-1, that makes loss repeatable
Enclosure type: The NEMA 250 rating (1, 3R, 4X, and so on) defining indoor versus weatherproof construction
Enclosure ventilation: Low opposing vents that let a gas leak escape instead of pooling in the cabinet
End bearing: Load carried by the base of the shaft pressing on firm soil or rock at the tip
End bearing vs friction: Load carried at the pile tip on firm soil versus load shed along the shaft into the soil
End hose: The flexible discharge hose the crew handles, and the part that whips under pressure
End of life: The 80 percent of rated capacity threshold at which a lead-acid string is replaced
End-suction pump: A base-mounted pump with axial suction and top discharge through a single impeller; the common mid-size hydronic pump
Energy audit: A systematic study of where a building wastes energy and money, ending in energy conservation measures ranked by payback.
Energy conservation measure (ECM): A specific change that cuts energy use, from a free schedule fix to a capital equipment replacement.
Energy reuse factor (ERF): The share of a data center's energy reused outside the facility, higher is better; relates to PUE via ERE = (1 minus ERF) times PUE
Energy-reducing maintenance switch (NEC 240.87): A means to put a breaker into no-intentional-delay mode during work so the arc clears fast, resolving the conflict between coordination delay and arc-flash energy
Engineering control: Source control at the tool: water to the cut, or a tool-mounted shroud on a HEPA dust collector, run ahead of any respirator
Engineering control (water vs vacuum): Source control by wetting the cut (water) or capturing dust with a tool-mounted HEPA collector (vacuum), ahead of any respirator
Engineering survey: The OSHA Subpart T assessment of the structure's condition and unplanned-collapse risk by a competent person before demolition, kept in writing.
Entanglement / protrusion: A projection that catches clothing or a drawstring; controlled by closing S-hooks, capping bolts, and the protrusion test
Enterprise data center: A facility an organization owns and runs for its own IT, single-tenant and owner-operated
Enthalpy: Total heat of the air, sensible plus latent, in Btu per pound, used by enthalpy changeover to account for humidity [https://anvilfield.com/field-guides/glossary/enthalpy/]
Enthalpy recovery effectiveness: The share of the total energy difference between exhaust and outdoor air that the recovery device transfers
Entitlement / zoning: The land-use approvals that allow a data center on a parcel, by right or by special exception, granted by the jurisdiction
Entrained air: Deliberate microscopic air bubbles that give freezing water room to expand, for in-service freeze-thaw durability [https://anvilfield.com/field-guides/glossary/entrained-air/]
Entrance facility: The entrance room where outside cabling enters the building
Entrapment response: The contracted, prioritized response to a passenger trapped in a stalled car, performed by the qualified mechanic, not building staff
Entrapment zone: Any place the moving gate can trap a person: leading edge, trailing or draw-in, hinge, or post
Entrapped air: Accidental large voids from mixing and placing that do not aid durability and are removed by vibration
Entrapped vs entrained air: Entrapped air is the unwanted voids consolidation removes; entrained air is the deliberate bubbles for freeze-thaw that it must not destroy
Entry point / breach: Where water actually crosses the membrane, often uphill of and away from the interior stain
Environmental sensor: A device measuring site conditions such as temperature, humidity, concrete maturity, silica dust, noise, or water
EOP: Emergency operating procedure, the response procedure for an abnormal or failure event
EOR: Engineer of record, who controls any crack repair that affects structural capacity [https://anvilfield.com/field-guides/glossary/eor/]
EPA 608: Federal certification required to service equipment containing refrigerant, by type or Universal [https://anvilfield.com/field-guides/glossary/epa-608/]
EPA-registered disinfectant / dwell time: A disinfectant registered with the EPA for a stated kill; dwell or contact time is how long it must stay wet on the surface to achieve it
EPDM: Ethylene propylene diene monomer, a thermoset rubber membrane with tape seams, the longevity and cold-flexibility leader [https://anvilfield.com/field-guides/glossary/epdm/]
EPMS: Electrical power monitoring system, the dedicated platform for power-chain metering and alarms, separate from the BMS [https://anvilfield.com/field-guides/glossary/epms/]
EPMS / DCIM: Electrical power monitoring system and data center infrastructure management, the systems that log power and temperature during the test
EPO: Emergency power off, the manual disconnecting means that drops the IT load and its support so a responder can enter a dead room
Epoxy / MMA: Two-component durable markings that cure by chemical reaction and bond flat to the surface
Epoxy grout: Three-component resin, hardener, and aggregate grout for dynamic, chemical, and high-precision service
Epoxy injection: Rigid, structural injection that welds a dormant crack back to monolithic strength
Epoxy vs cementitious terrazzo: Epoxy uses a thin bonded resin matrix; cementitious uses a thicker portland cement matrix, bonded or isolated from the slab
EPSS: Emergency power supply system: the source, prime mover, transfer equipment, and controls taken together under NFPA 110 [https://anvilfield.com/field-guides/glossary/epss/]
Equal friction: The residential sizing method that holds the same friction rate across every run, dropping velocity as the trunk reduces
Equilibration: The wait, commonly at least 24 hours, while the probe air balances with the concrete
Equilibrium density: In-service density after drying to a stable moisture, the basis for ACI 213 bands, per ASTM C567
Equipment / asset: The specific panel, unit, or circuit worked on, with nameplate where possible
Equipment class (A1-A4): ASHRAE rating that sets a device's allowable temperature and humidity band [https://anvilfield.com/field-guides/glossary/equipment-class-a1-a4/]
Equipment grounding conductor (EGC): The conductor that bonds the generator frame and enclosures to the grounding system; required regardless of the SDS question [https://anvilfield.com/field-guides/glossary/equipment-grounding-conductor-egc/]
Equipment telematics: Machine-reported data including GPS location, engine hours, idle time, fuel, and fault codes
Equipment warranty: The manufacturer's promise that the parts are free of defects for their term. Defective parts route to a manufacturer claim, often with a labor allowance. Terms vary by manufacturer.
Equipotential: The condition where bonded parts sit at the same potential, so no noise, fault, or surge current is driven between them
Equipotential bonding: Tying all pool metal and the water to the same voltage under NEC 680 so there is no difference to shock a swimmer [https://anvilfield.com/field-guides/glossary/equipotential-bonding/]
Equivalent age: The Arrhenius maturity index, time at a reference temperature, in hours
Equivalent diameter: The round duct size that carries the same airflow at the same friction rate as a given rectangular duct
Equivalent leakage area (ELA): The total of all the room's gaps expressed as one equivalent opening, the door fan test's core measurement
Equivalent length: The feet of straight duct that would cost the same static pressure as a given fitting, read from the Manual D tables [https://anvilfield.com/field-guides/glossary/equivalent-length/]
ERCES / BDA: Emergency responder communication enhancement system, the public-safety system; BDA is its bidirectional amplifier
ERE: Energy Reuse Effectiveness, PUE adjusted for energy exported for reuse, which can fall below 1.0
Erection / dismantling: Building up and taking down the machine, the most dangerous phase, done by a manufacturer-trained crew to a set sequence
Erection drawings: The manufacturer's set with frame lines, part marks, bracing, connections, panel layout, and the erection sequence
Erection sequence / EOR: The engineered order of raising the frame to keep it stable; the engineer of record designs the structure and connections, the erection engineer the means of raising it
ERF: Energy reuse factor, the share of energy sent off-site for reuse, 0.0 to 1.0
ERMS / ARMS: Energy-reducing maintenance switch, a second trip setting that lowers clearing time and arc-flash energy during work
ERMS / maintenance mode: Energy-reducing maintenance switch; a worker-flipped mode that drops the instantaneous pickup for faster clearing during energized work
Erosion control: Measures that keep soil from detaching in the first place, such as cover, mulch, seed, and blankets
Erosion corrosion: Pipe wall and fitting wear from velocity above the limit, seen as grooves and pinholes at elbows [https://anvilfield.com/field-guides/glossary/erosion-corrosion/]
Erosion-corrosion: Wall thinning in copper from high-velocity hot water, worst at fittings and direction changes
ERV / HRV: Energy recovery ventilator transfers heat and moisture (total energy); heat recovery ventilator transfers heat only (sensible)
ESAL: Equivalent single axle load: damage equal to one pass of a standard 18,000 lb single axle on dual tires
ESALs: Equivalent single axle loads, the traffic measure that sets Ndesign
Escalation: The rise in material and labor cost over a long schedule, priced separately from contingency and supported by a published index or actual cost.
Escalation clause: The annual price increase that keeps a multi-year agreement profitable as costs rise
ESCS: Expanded shale, clay, and slate, the kiln-bloated aggregate used in most structural lightweight
ESOP: Employee stock ownership plan, a trust-based sale of the company to its employees
ESP: External static pressure, the resistance the blower works against outside the cabinet, in inches of water column [https://anvilfield.com/field-guides/glossary/esp/]
ESP (rated): The maximum external static pressure the equipment's blower is rated to push against, from the blower table
ESP / PRP / COP: ISO 8528 ratings: emergency standby, prime, and continuous power
ESP / TESP: External static pressure; TESP is the total across both sides of the air handler, return plus supply as magnitudes
ESR: ICC-ES evaluation report stating a post-installed anchor's seismic and cracked-concrete qualification and its capacities [https://anvilfield.com/field-guides/glossary/esr/]
ESR / AC308: The ICC-ES evaluation report and its acceptance criteria, where the design values and conditions live
Establishment: The one to three years after planting when a tree depends on supplemental water, roughly one year per inch of caliper [https://anvilfield.com/field-guides/glossary/establishment/]
Establishment period: The first one to two growing seasons after planting, the most intensive maintenance phase, when survival is decided
Estimate class: AACE's classification of an estimate by design maturity, Class 5 conceptual to Class 1 definitive, which sets the expected accuracy range. [https://anvilfield.com/field-guides/glossary/estimate-class/]
Estimate to complete (ETC): The honest cost still to come on a job; the judgment input that drives the whole schedule
ET / ETo / ETc: Evapotranspiration: reference demand ETo scaled by a crop coefficient to the plant need ETc [https://anvilfield.com/field-guides/glossary/et-eto-etc/]
eta: Stratification efficiency, the usable fraction of the tank volume, commonly 0.85 to 0.95
Ethylene glycol: The lower-viscosity glycol with better heat transfer and a lower freeze point, but toxic, so it is kept out of occupied potable-risk systems
ETo: Reference evapotranspiration, the water demand of a standard surface under the day's weather
EUI / benchmark: Energy use intensity, a building's annual energy per square foot in kBtu, compared against similar buildings to judge performance.
Ev: System ventilation efficiency, the multi-zone correction for shared outdoor air
Evacuation: Pulling a deep vacuum on an open system to remove air, moisture, and non-condensables before charging [https://anvilfield.com/field-guides/glossary/evacuation/]
Evacuation hose: A large-bore hose, 3/8 in or 1/2 in, that moves gas at vacuum far faster than a 1/4 in refrigeration hose
Evaluation report: The third-party report (such as ICC-ES or IAPMO-UES) that qualifies the coupler system and bounds its use
Evaporation rate: The water leaving the fresh surface per area per time, read from the ACI chart; precautions apply near 0.2 lb/sq ft/hr [https://anvilfield.com/field-guides/glossary/evaporation-rate/]
Evaporation retarder: A monomolecular film sprayed on the plastic surface to slow drying between finishing passes; not a curing compound [https://anvilfield.com/field-guides/glossary/evaporation-retarder/]
Evaporator: The cold plate or surface where the fluid boils and takes heat off the chip
Evapotranspiration (ET / ETo): Water lost from soil and plants to the air; reference ET (ETo) is the loss from a standard grass surface, the demand a controller replaces
Evapotranspiration (ET): Water lost from soil and plants to the air; what a weather-based smart controller waters to
EVEMS: EV energy management system that limits charger draw to hold the service under its rating
Evergreen / auto-renewal: A clause that renews the agreement automatically unless the customer gives notice in a stated window
EVI: Enhanced vapor injection, a mid-compression vapor port that holds heat-pump capacity in the cold
EVPN-VXLAN: The overlay that tunnels tenant traffic between leaves over the routed underlay
EVSE: Electric vehicle supply equipment, the charger, treated as a continuous load under Article 625 [https://anvilfield.com/field-guides/glossary/evse/]
EVT: Equiviscous temperature, the asphalt temperature for proper mopping viscosity, applied within plus or minus 25°F [https://anvilfield.com/field-guides/glossary/evt/]
EWIF: Energy water intensity factor, liters of water per kWh of generated electricity, used to compute source WUE
EWT / LWT: Entering and leaving water temperature at the heat pump, in °F; their difference is the water-side delta-T
Excess air: Combustion air beyond the stoichiometric minimum; commonly around 15 percent (about 3 percent flue O2) on a tuned gas burner [https://anvilfield.com/field-guides/glossary/excess-air/]
Exchange rate: The dB increase that halves the allowed time: 5 dB for OSHA, 3 dB for NIOSH [https://anvilfield.com/field-guides/glossary/exchange-rate/]
Exclusion: A physical barrier that keeps the animal off the plant: fencing, tree guards, cages, netting; the only layer that reliably holds under high pressure
Exclusion / drop zone: The area where material can fall, the machine can swing, or a collapse can reach, kept clear of people during active demolition.
Exclusion zone: The barricaded, cleared area behind every live tendon and the jack during stressing
Exhaust: High vents at or near the ridge that let hot, moist air out
Exhaust ventilation: Mechanical removal of air from a space to carry off odor, moisture, heat, or contaminants and set its pressure
Existing conditions: The pre-existing state and damage photographed before work starts, the set that protects you from being charged for what you inherited
Exit options: The paths out: family transfer, management buyout, ESOP, third-party sale, merger, or wind-down
Exoskeleton: A worn frame that supports the body to reduce strain and musculoskeletal injury; it does not detect or alarm [https://anvilfield.com/field-guides/glossary/exoskeleton/]
Exothermic weld: A permanent molecular bond formed by a controlled reaction, accepted for connecting to rebar in concrete [https://anvilfield.com/field-guides/glossary/exothermic-weld/]
Expansion fitting: A busway section that absorbs thermal length change on a long or anchored run
Expansion joint: A full gap through the structure that lets parts move apart and back, mainly for thermal and moisture movement
Expansion joint / bearing: The joint that lets the deck move and the bearing the structure sits on; a leaking joint corrodes the bearing below
Expansion joint cover: The factory or field assembly of a bellows and two metal flanges that spans the curbs and flashes to the membrane on each side
Expansion loop: A U of pipe built into the run that flexes to absorb growth
Expansion offset: A Z-shaped jog that flexes to take movement in less space than a loop
Expansion splice plate: A slotted joint that lets a tray run slide as it grows and shrinks with temperature
Expansion tank: A bladder tank that absorbs the volume growth of heated water in a closed system [https://anvilfield.com/field-guides/glossary/expansion-tank/]
Expansion-joint cover: The manufactured assembly that bridges the open gap, carries traffic or finish, and still allows the movement
Expellant cartridge: The sealed nitrogen or CO2 cylinder punctured on actuation to push the agent out of the tank
Explosionproof / flameproof: An enclosure that contains an internal explosion and cools the escaping gas below ignition so it cannot light the outside atmosphere
Exposed / through-fastener panel: A metal panel screwed through its face, where the screws and their rubber washers are the common leak [https://anvilfield.com/field-guides/glossary/exposed-through-fastener-panel/]
Exposure: The portion of each shake or shingle left to the weather, set by the piece length and the slope per the manufacturer [https://anvilfield.com/field-guides/glossary/exposure/]
Exposure assessment: The alternative path: monitor the air and keep exposures at or below the PEL when you do not follow Table 1
Exposure class: The code category for freezing and deicer exposure that sets the minimum air and maximum water-cement ratio [https://anvilfield.com/field-guides/glossary/exposure-class/]
Exposure control plan: The required written document describing the tasks, controls, housekeeping, and restricted access for the job [https://anvilfield.com/field-guides/glossary/exposure-control-plan/]
Extended labor warranty: A purchased program that reimburses labor the base manufacturer warranty does not cover
Extension spring: Spring along each horizontal track that stores energy by stretching as the door closes
Extensive: Shallow media (~2 to 6 in), sedum and groundcovers, low load (~15 to 30 psf saturated), low maintenance
Extensive vs intensive: Extensive is shallow media and sedum with low maintenance; intensive is deep media and garden plantings with high, garden-level maintenance
External equalizer: A line feeding coil-outlet pressure to the TXV diaphragm, needed on distributor and high-drop coils
External static pressure: Air-side pressure the blower works against, in inches of water column
External static pressure (ESP): The resistance the fan works against, in in. w.c., summed from grille, duct, dampers, screen, and cap
Extraction: Mechanical removal of standing water, which pulls out far more water than evaporation
Ez: Zone air distribution effectiveness, how well supply air reaches the breathing zone
F: Leakage rate in cfm per 100 sq ft of duct surface at the test pressure
f prime c: Specified compressive strength, the design strength on the drawings, referenced at the specified age and given in psi or MPa
f prime cr: Required average strength, the higher target the mix is proportioned to so the acceptance statistics pass, set from f prime c and the producer's variability
F rating / T rating: Hours the firestop holds flame back, and hours before the unexposed side rises about 325°F
f'c: Specified compressive strength on the drawings, judged at the specified age, commonly 28 days [https://anvilfield.com/field-guides/glossary/f-c/]
f'cr: Required average strength the mix is proportioned to, set above f'c to absorb normal test scatter [https://anvilfield.com/field-guides/glossary/f-cr/]
F-number: Unitless, linear statistical index for flatness or levelness; an FF50 floor is twice as flat as FF25
f-prime-c: Specified compressive strength of the concrete, in psi, from the cylinder break
F-rating: Time a firestop holds back flame on the unexposed side, per ASTM E814 / UL 1479; must match the barrier rating
f100: Friction loss in feet per 100 ft of pipe at the design gpm, read from a friction chart for the pipe size and material
FAA marking / lighting: Obstruction paint and beacons such as the L-864 required above the trigger height per FAA AC 70/7460-1
FAA Part 107: The US federal rule for commercial small drone operation, requiring a remote pilot certificate, a registered aircraft, and compliance with the airspace and operating rules.
Fabric validation: Link-by-link confirmation that the high-speed network is up at rated speed with error counters inside threshold
Face plate: The front of a water closet carrier the bowl seals and bolts to, usually adjustable up and down to set the fixture height
Face velocity: The inward air speed across the hood opening, in fpm, commonly near 100, the working proxy for capture
Face weight: The weight of the fiber alone per square yard in ounces, a proxy for density and durability
Face-frame: Construction with a solid wood frame on the front of the box; stiffens the box and gives material to scribe at the wall
Face-lit vs halo: Face-lit glows through a translucent acrylic face; halo (reverse-lit) is solid-faced with rear LEDs that glow on the wall
Face-shell bedding: Mortar on the outer face shells only; full bedding adds mortar on the webs where the cell is grouted
Facet: A single roof plane; the facet count is a quick read on how cut-up the roof is
Facility operations: Running and maintaining the building over its service life, the job the twin serves
Facility vs cluster Cx: Facility commissioning proves the building's power and cooling; cluster commissioning proves the compute on top of it
FACP / FACU: Fire alarm control panel, or control unit, the system's brain that monitors inputs and drives outputs
Factory startup: The manufacturer-authorized first start required to keep the chiller warranty intact
Fadjust: Adjustment factor for more than three current-carrying conductors, NEC 310.15(C)(1)
Fail-safe: On a listed valve, closing the hot port if the cold supply is lost, so the outlet does not run full-hot
Fail-safe / fail-secure: A lock that releases on power loss, versus one that stays locked on power loss
Fail-safe vs fail-secure: Fail-safe unlocks on power loss; fail-secure stays locked on power loss. The choice is a per-door life-safety and security decision
Failover / failback: Switching production to the recovery site, and returning it to the primary after recovery
Fall clearance: The total room needed below the anchor to arrest a fall before the worker hits a lower level
Fall detection / man-down: A wearable that senses a fall or a no-motion condition and auto-alerts with a location
Fall-of-potential: A ground-resistance test method that is awkward on a CEE because the electrode is tied into the structure [https://anvilfield.com/field-guides/glossary/fall-of-potential/]
False alarm / ECV: A signal with no real intrusion; enhanced call verification places at least two calls to different numbers before a dispatch is requested
Fan array / fan wall: A grid of small direct-drive plenum fans in an AHU bulkhead, replacing one large housed fan
Fan curve: The manufacturer plot of airflow against static at a given speed, used to confirm the fan is at its design point [https://anvilfield.com/field-guides/glossary/fan-curve/]
Fan laws / affinity laws: The ratios linking fan or pump speed to airflow, pressure, and power
FAR / FRR: False accept rate and false reject rate, the biometric tradeoff between letting the wrong person in and locking the right one out
Fascia: The vertical board at the roof edge closing the rafter tails and carrying the gutter
FAST diagram: Function Analysis System Technique, a how-and-why map of a project's functions used to find high-cost, low-value functions
Fast-track: Overlapping design, permit, procurement, and construction to compress the schedule to the lease date
Fastener upsize: Replacing a wallowed screw with the next larger diameter and a fresh gasketed washer so it bites fresh metal
FAT: Factory acceptance test, the witnessed test of equipment at the manufacturer before shipment, the Level 1 step [https://anvilfield.com/field-guides/glossary/fat/]
Fatigue (alligator) cracking: Interconnected wheelpath cracking from repeated load on a structure that cannot carry it; a base failure
Fault prioritization: Ranking faults by energy cost, comfort, and risk so the team fixes what matters instead of every alarm
Fault tolerance: Surviving a single unplanned failure with the load untouched, the Tier IV behavior, beyond concurrent maintainability
Fault tolerant: Survives a single unplanned failure with the load untouched, the Tier IV test [https://anvilfield.com/field-guides/glossary/fault-tolerant/]
Faulting: A vertical step at a transverse joint from lost load transfer and pumping
Faying surface: The contact area between plies; Class A is 0.30, Class B is 0.50 slip coefficient
FCO / WCO / CO: Floor cleanout, wall cleanout, and a plain cleanout for rodding access
FCU: Fan coil unit, a terminal fan-and-coil that conditions one zone from central water or its own refrigerant
FDC: Fire department connection; the exterior inlet where the fire department pumps water into the system [https://anvilfield.com/field-guides/glossary/fdc/]
FDD: Fault detection and diagnostics, software that reads BAS trend data to find faults and name the likely cause [https://anvilfield.com/field-guides/glossary/fdd/]
Featheredge: Where the pour tapers to nothing at a high spot or transition; thins below minimum depth and gets fragile
Federated model: The combined model that overlays every trade's model in one shared space for clash detection, without merging the source files
Feeder: Conductors from the service or source to the final branch-circuit overcurrent device
Feeder busway (bus duct): Busway with no tap points, used to move power from source to area as a high-current run
Feeder OCPD: The overcurrent protective device protecting the feeder; every tap ampacity floor (1/10, 1/3) is keyed to its rating
Feeder vs plug-in busway: Feeder has no tap openings and moves power point to point; plug-in has tap openings along its length for rack power
Ferrous raceway: Steel raceway or enclosure, where an unbalanced field induces heating, addressed at 300.20(A)
FF (floor flatness): ASTM E1155 index of short-distance bumpiness from slope change over 12 in intervals; higher is flatter
FF / FL: Floor flatness and levelness F-numbers measured under ASTM E1155, lowered by curling after placement [https://anvilfield.com/field-guides/glossary/ff-fl/]
FF / FL (ASTM E1155): Floor flatness and levelness numbers; higher FF is a flatter floor
FFU: Fan filter unit, a combined fan and HEPA or ULPA module set into the ceiling grid
Fiber-reinforced concrete (FRC): Concrete with discrete fibers mixed throughout to control cracking and add post-crack toughness
Field / perimeter / corner: Roof zones by uplift, lowest in the field and highest at the corners
Field leadership: Running a crew at the point of work: the daily planning, make-ready, safety, productivity, schedule, and people decisions that turn an estimate into installed work
Field measure: The as-built dimensions taken on site after the walls are up, that the shop builds to instead of the plan
Field of view (FOV): The angle and width of the scene the lens captures; set by focal length, and it determines the ppf at a given distance
Field service management (FSM): Software built for businesses that dispatch crews to properties, combining CRM with scheduling, jobs, and invoicing
Field-cured: Cylinders cured with the structure to judge in-place strength for stripping or loading [https://anvilfield.com/field-guides/glossary/field-cured/]
Field-cured cylinder: A test cylinder cured beside the structure under the same conditions, used to read in-place strength, not for design acceptance
Figure of merit: A score comparing delivered cooling to the ideal for a perfectly stratified tank
Fill: The splash or film media that spreads the water for maximum contact with the air
Fill percent: Sum of cable cross-sectional areas divided by the usable tray area, times 100, against the 392.22 limit
Fill valve / PRV: The pressure reducing valve that drops building water to loop fill pressure and feeds make-up only when the loop drops below its setpoint
Filled weight: The dead load of the pipe plus its contents plus insulation, in pounds per foot, that the support is sized to carry
Filling ability: The mix flowing out and filling the form under its own weight, read on the slump flow
Film-forming coating: A topical sealer or coating that sits on the surface as a layer, giving sheen and a barrier but able to peel
Film-tearing bond (FTB): The weld acceptance where a peeled sample tears the membrane before the seam opens
Filter drier: A desiccant-filled component that catches the trace moisture left after a proper vacuum; a backup, not a substitute
Filter fabric / geotextile: A non-woven fabric that separates soil from drainage gravel, passing water while holding back the fines
Filter integrity test: In-place DOP or PAO aerosol scan of an installed filter for leaks in media, frame, and seal
Filter-drier: The liquid-line shell that removes moisture, acid, and particulate from the refrigerant
Filtration: Letting water pass across the fabric while holding soil particles in place, balancing flow against retention.
Final completion: The milestone where the punch is closed, all closeout documents are in, and final payment with remaining retention is released
Final test: The test after fixtures are set, proving the finished DWV system gastight, including the smoke and peppermint methods
Finaled: A permit closed in the building department's records after all inspections are signed off
Finance attach rate: The share of jobs that get financed, the clearest read on whether the team offers it
Financing / monthly payment: Spreading the price into a monthly payment that removes the sticker-shock price wall
Findings: What you actually discovered on site, which often differs from the report
Fines: The silt and clay-sized material passing the #200 sieve; binds the stone in the right amount, pumps in excess
Finish grade: The surface elevation when the job is done, carrying the drainage slope; rough grade is left low for topsoil [https://anvilfield.com/field-guides/glossary/finish-grade/]
Finished floor height (FFH): The clear plenum depth from the slab to the top of the finished panel
Finned-tube coil: A heat exchanger of tubes through stacked metal fins, with fluid inside the tubes and air across the fins
Fins per inch (FPI): How tightly the fins are packed along the tube; higher FPI adds heat transfer and pressure drop and clogs faster
Fire and smoke restoration: Cleaning and rebuilding a building after a fire, covering the char, the soot, the odor, and the firefighting water [https://anvilfield.com/field-guides/glossary/fire-and-smoke-restoration/]
Fire damper (FD): Closes on heat to stop flame and heat through a fire-rated barrier; listed to UL 555
Fire door / fusible link: A rated rolling door released to close on an alarm or by a heat-melted link, drop-tested per NFPA 80
Fire feature: A fire pit or outdoor fireplace built into a yard, wood-burning or gas
Fire pit / outdoor fireplace: An open ring or bowl, versus a masonry firebox with a chimney that drafts smoke up
Fire prevention program manager (FPPM): The boots-on-the-ground person required by NFPA 241 to run the construction fire prevention program
Fire pump: A listed stationary pump built to NFPA 20 that boosts water pressure and flow for fire protection, idle until a fire demand calls it
Fire sprinkler system: A network of pipe and heat-activated sprinklers that delivers water to a fire; heads open individually over the fire
Fire watch: A trained person assigned only to watch for fire during hot work and after it stops, with a charged extinguisher and the authority to stop the work [https://anvilfield.com/field-guides/glossary/fire-watch/]
Fire-rated assembly: A complete tested system, board type and layers, framing, fasteners, and firestop, that carries a fire-resistance rating only when built exactly as tested
Fire-rated joint: A tested joint system, commonly to UL 2079, that keeps a fire barrier rated while the joint moves
Fire-resistance rating: The hours an assembly was proven to resist a standard fire test, set by the building code by type and member
Fire-retardant treatment / WUI: Pressure-impregnated chemicals that raise the fire class; the wildland-urban interface where wood roofs are often restricted or banned
Firefighters' emergency operation: Phase I automatically recalls the cars to a designated floor on a fire alarm; Phase II gives a firefighter manual control of a car
Firestop: The separate trade that seals penetrations through rated walls and floors, tested to ASTM E814 or UL 1479 [https://anvilfield.com/field-guides/glossary/firestop/]
Firestop system: A tested, listed assembly of barrier, penetrant, and materials that restores a fire rating, identified by a directory system number
First cost: The initial cost to build the pavement, usually per square yard, before any maintenance
First draw: A sample taken after water has sat in the plumbing for hours, showing worst-case lead contact
First number: Configuration code for voltage, poles, and wires; 5 is 125V, 6 is 250V, 10 is 125/250V ungrounded, 14 is 125/250V grounded
First-flush diverter: Device that discards the dirtiest opening runoff of a storm before the cistern
First-hour rating (FHR): Gallons a storage heater delivers in one hour from full: usable storage plus recovery
First-time fix rate: The share of jobs resolved on the first visit, which rises as the callback rate falls
First-time fix rate (FTFR): The share of service calls resolved completely on the first visit, with no return trip [https://anvilfield.com/field-guides/glossary/first-time-fix-rate-ftfr/]
First-work / mockup: Inspection and approval of the first unit of a repeated operation, which becomes the benchmark for the rest
First-work inspection / mock-up: The inspection of the first piece, or a built sample, that sets the agreed standard for the rest of the work
Fixed dock: A dock built on pilings with the deck at a set height above the water, suited to a stable water level
Fixed point: The single location where a panel is anchored, so it expands in a controlled direction
Fixed vs PTZ: A fixed camera holds one view; a PTZ pans, tilts, and zooms to cover several views from one device
Fixture assembly: One fixture priced as a kit: the fixture, its rough-in, stops, trap, carrier, and labor
Fixture carrier: The concealed steel frame that supports a wall-hung fixture and carries its load to the floor, covered in the fixture rough-in guide [https://anvilfield.com/field-guides/glossary/fixture-carrier/]
FL (floor levelness): ASTM E1155 index of tilt and dishing from elevation difference over 10 ft; valid only on grade or shored slabs
FLA: Nameplate full-load amps of the motor, the basis for the overload setting under NEC 430.32 [https://anvilfield.com/field-guides/glossary/fla/]
FLA (full-load amps): The current stamped on the motor nameplate; sizes the overload only, under 430.32
FLA vs FLC: Nameplate full-load amps sets the overload; table full-load current sizes the conductor and fault device
Flagging: A whole branch browning out while the rest of the canopy holds, a stress or dieback signal
Flame rectification: How a flame sensor proves flame, by the tiny DC current a lit flame passes to ground
Flame safeguard: The control that proves flame before opening the main gas valve and locks out on flame failure
Flame-spread / smoke-developed: Burn-behavior ratings for the material, commonly held to 25 and 50 under the referenced listings
Flare: The sloped side of a perpendicular ramp, walkable at 10 percent (1:10) maximum [https://anvilfield.com/field-guides/glossary/flare/]
Flash coat: A thin final sprayed layer for uniform texture over a cut or troweled surface; cosmetic, not structural
Flash cove: Sheet flooring run up the wall as an integral, weldable sanitary base
Flash gas: Liquid that boils to vapor in the liquid line when pressure drops below its saturation point, starving the metering device [https://anvilfield.com/field-guides/glossary/flash-gas/]
Flash point: The temperature at which a fluid gives off enough vapor to ignite; it sets the fire-code classification
Flash steam: Steam that re-forms when hot condensate at pressure drops to a lower pressure, normal and not a trap failure
Flashback arrestor: An oxy-fuel device that stops a flame front from traveling back through the hose to the regulator and cylinder
Flashing: Metal or membrane that sends water to the face of the WRB instead of into the wall at openings and joints
Flashing flange / clamping ring: The part that clamps a floor membrane to the drain body for a watertight seal
Flat rate: One agreed price for the task, set before the work and fixed regardless of how long it takes
Flat saw / slab saw: Walk-behind diamond saw for horizontal surfaces like floors and pavement
Flat-oval: Round duct flattened to fit a shallow space, keeping most of round's strength
FLC: Table full-load current from the NEC, used to size the conductor and short-circuit device [https://anvilfield.com/field-guides/glossary/flc/]
FLC (full-load current): The table current from NEC 430.250 or 430.248 by horsepower and voltage; sizes the conductor and the branch device
Fleet safety program: The written policy and daily practices a company uses to prevent crashes by its drivers and vehicles, distinct from DOT regulatory compliance
Flex duct: Insulated flexible duct: a wire helix and liner inside insulation and a vapor jacket
Flex tech / flex capacity: A truck or slot held open to absorb same-day and emergency work without breaking the booked board
Flexible connector: A bellows or braided pipe section at the suction and discharge that absorbs movement and keeps pipe strain off the pump flanges
Flexible coupling: The element joining the pump and motor shafts; it absorbs a small residual, not a real misalignment
Flexible pavement: Asphalt pavement, which bends and spreads load down through its layers to the subgrade
Flexure wood (thigmomorphogenesis): Extra wood a tree grows in response to wind flexing and load, building trunk strength and taper; distinct from reaction wood, which forms in response to a lean.
Float: Opens and levels the surface, bringing the cream up; magnesium opens, wood pulls paste
Float (slack): The time an activity can be delayed before it matters; critical activities have zero float
Float / overflow switch: A water-level device that shuts the unit down before the pan overflows
Float current: The small current a charger pushes to hold a string full; a rising value warns of runaway
Float voltage: The steady charge voltage held on the battery, temperature-compensated for lead-acid
Floating / sliding clip: A two-piece clip that holds the panel down but lets the seam slide for thermal movement
Floating dock: A dock that rides on flotation and rises and falls with the water, suited to tidal or fluctuating levels
Floating neutral: A generator with no neutral-to-frame bond; both output conductors are treated as live, used so the only bond can be elsewhere [https://anvilfield.com/field-guides/glossary/floating-neutral/]
Flood coat: The heavy top pour of bitumen that receives the gravel surfacing
Flood cut: Removing drywall a set height above the water line, commonly 12 to 24 inches, so the cavity can dry or be decontaminated
Flood level rim: The top edge of a fixture where it would overflow; stack AAV height is referenced to the highest fixture's rim
Flood rim: The level at which a fixture overflows, the reference for which fixtures are at risk in a backup
Flood test: Plugging and filling the pan to prove the waterproofing holds before tile goes down [https://anvilfield.com/field-guides/glossary/flood-test/]
Flood-level rim: The top edge a receptor can fill to before overflowing, the reference for the air gap and air break
Floodback: Liquid refrigerant returning down the suction line toward the compressor
Floodback / slugging: Liquid returning while running, or liquid in the compression chamber, usually on a flooded start
Flooded suction: An arrangement where water sits above the pump and feeds it by gravity, giving positive static head and the most NPSHa
Floor sink: A deep, cleanable receptor set flush with the floor with a removable grate, built to take indirect waste
Floor surface temperature: The temperature of the finished floor surface, held to about 80 to 85°F for comfort, which caps output
Flow center: The circulator pump package that moves loop fluid at the design gpm against the loop pressure loss
Flow cone: ASTM C939 test timing how long fluid grout flows through a standard cone, an efflux time
Flow control: The vented fitting that limits flow to the rated GPM so the trap can separate grease
Flow line: The low invert of the gutter where the pan meets the curb face; the line water follows, graded to drain
Flow loop: The control loop that drives the damper to make the airflow setpoint the temperature loop calls for
Flow rate: The volume delivered over time, in gpm, what a clog cuts while the static pressure can stay normal
Flow restrictor: An orifice, weir, or control-flow drain that throttles the roof's discharge to the allowable rate
Flow ring / cross: The multi-point averaging sensor at the box inlet that reads total and static pressure to derive velocity pressure
Flow sensor: A mainline meter that lets the controller detect abnormal flow and shut off through the master valve on a break
Flow station: A permanent venturi or orifice with a calibrated pressure-drop-to-flow curve, used where a balancing valve is not in the line
Flow-down: A clause making the sub responsible to the GC for the same obligations the GC owes the owner under the prime contract
FLSA: Fair Labor Standards Act, the federal law setting overtime at over 40 hours in a workweek
Flue gas dew point: Temperature at which flue gas water vapor condenses, roughly 130 to 140 degrees F on natural gas; return must be below it to condense
Fluid service category: The B31.3 classification (Category D, Normal, Category M, high pressure) that sets construction and examination rigor
Fluid trap / knockout: Vessel ahead of the pump that drops liquid out of the airstream before it reaches the machine
Flushometer: A flush valve that meters a measured flush to a water closet or urinal directly from the pressurized supply, with no tank [https://anvilfield.com/field-guides/glossary/flushometer/]
Flushometer vs flush tank: A valve flushing a closet directly in a short high-flow burst versus a slow-filling tank; the two read different demand lines and need different residual pressure
Flute / rib: The corrugation in a steel deck; you fasten into the top flute, not the open valley
Fluting: Washboard pattern of ridges across the race, the late stage of shaft-current damage
Flying / table form: A large slab-form table flown by crane floor to floor on repetitive elevated decks
Flywheel: Kinetic storage that rides through on a spinning mass, commonly 10 to 30 seconds, with no chemistry
FM: Frequency multiplier, for how often the lift is repeated and for how long
FM 1-60 / 1-90 / 1-120: FM Approvals windstorm classification: the psf the assembly resisted in test, before the safety factor of 2
FMC / LFMC / LFNC: Flexible metal conduit (dry), and liquidtight flexible metal and nonmetallic conduit (wet)
Foamed asphalt: Hot asphalt cement foamed with a small dose of cold water so it coats fines and binds at low temperature [https://anvilfield.com/field-guides/glossary/foamed-asphalt/]
Focus Four: Falls, struck-by, caught-in or between, and electrocution, the hazards behind most construction deaths
Focus Four / Fatal Four: OSHA's four leading construction killers: falls, struck-by, caught-in/between, and electrocution
FOG: Fats, oils, and grease, the regulated material the interceptor is built to capture [https://anvilfield.com/field-guides/glossary/fog/]
Fog seal: A light spray of diluted asphalt emulsion on existing pavement to seal the surface, bind raveling, and slow oxidation
Fogging: A fine mist held above the slab to raise local humidity and cool the air, slowing surface evaporation
Foot valve: A one-way check and screen at the bottom of a suction line that holds prime and keeps debris out
Footage counter: The reel meter reading how far the camera head has traveled into the line
Footcandle (fc): Illuminance of one lumen per square foot, the US unit on most drawings [https://anvilfield.com/field-guides/glossary/footcandle-fc/]
Footcandle (fc) / lux: Light at a surface; lumens per square foot. 1 fc is about 10.8 lux
Footcandle / lux: Illuminance at a surface; 1 fc is about 10.76 lux
Footprint: The flat outline of the building, always smaller than the sloped roof above it
Force account: T&M work tracked on a daily ticket signed by the owner's representative the day it happens; the signed ticket is the claim
Force main: The pressurized pipe that carries pumped sewage from the station to the point where it can flow by gravity again [https://anvilfield.com/field-guides/glossary/force-main/]
Force reduction / shock absorption: How much impact the surface takes out versus a rigid floor, a tested certification metric
Forebay: A small settling pool at the inlet that catches coarse sediment before it spreads across the basin, making cleanout easier [https://anvilfield.com/field-guides/glossary/forebay/]
Foreman: The person who leads one crew at the point of work and links the field to the office; closest leader to the tools
Form: A manufacturer designation, such as Form 7 or Form 8, for the body and cover style; bodies and covers must share the form to seat
Form face / sheathing: The surface the concrete sets against, which decides the finish: plywood, overlaid plywood (MDO/HDO), steel, plastic, or a lined face
Form I-9: The employment-eligibility verification required for every employee at hire
Form tie: The tension member holding the two faces of a wall form against the lateral concrete pressure and setting the wall thickness [https://anvilfield.com/field-guides/glossary/form-tie/]
Form-saver: A threaded coupler mounted at the form face so a dowel can be threaded in for the next pour
Formicary corrosion: Ant-nest corrosion that bores through copper tube from the inside out, driven by organic acids from off-gassing materials
Formwork: The whole system that supports fresh concrete: the mold plus shores, reshores, bracing, and hardware
Formwork (shuttering): The temporary mold and framing that shapes fresh concrete and holds it until it sets; shuttering is the same thing in British usage
Forward / reverse phase: Leading-edge (TRIAC, incandescent/MLV) and trailing-edge (ELV, LED/electronic) line-voltage dimming
Fp: The seismic design force on a nonstructural component, calculated by the engineer per ASCE 7 Chapter 13
FPSF: Frost-protected shallow foundation, insulated so a shallow footing does not heave
FPT: Functional performance test, the witnessed demonstration that a system performs its sequence under normal and fault conditions [https://anvilfield.com/field-guides/glossary/fpt/]
FR: Friction rate, the design pressure drop per 100 ft of duct, in inches of water column per 100 ft
Fractionated RAP: RAP screened into size fractions so the designer can control gradation and binder contribution
Frame: The NEMA dimension code fixing shaft height, shaft, and bolt pattern
Frameless (32mm): European construction with no face frame; hardware mounts to a 32 mm hole grid; more interior room, tighter install tolerances
Free area: The actual open portion of a grille or louver face that air passes through, less than the nominal size
Free chlorine / ORP: Free chlorine is the sanitizer still available to kill, in ppm; ORP is the water's oxidizing power in mV, tracking kill speed
Free chlorine residual: The active disinfecting chlorine left in the water, read in mg/L by a test kit; the figure the standards specify
Free cooling: Rejecting heat using cool outside air or a low wet-bulb instead of running mechanical chillers, which lowers power and water [https://anvilfield.com/field-guides/glossary/free-cooling/]
Free egress: The requirement that occupants always exit a controlled door without a key, credential, code, or tool, usually with one releasing motion [https://anvilfield.com/field-guides/glossary/free-egress/]
Free fall: The distance a worker falls before the system begins to arrest, limited to 6 ft
Free float: How long an activity can slip without delaying the start of the next activity
Free water: Water available to the paste, excluding water absorbed into dry aggregate; this is the water Abrams' law counts
Freeboard: The vertical distance between the design high-water level and the top of the embankment, a safety margin against overtopping [https://anvilfield.com/field-guides/glossary/freeboard/]
Freeze vs burst protection: Freeze protection keeps the fluid pumpable at the low temperature; burst protection only keeps it from splitting the pipe as slush, and needs far less glycol
Freeze-drying documents: Vacuum sublimation that turns ice to vapor so wet paper dries without swelling or running
Freezer floor heave: Upward cracking of a freezer slab when the ground below freezes and forms expanding ice lenses.
Freezestat: A low-temperature limit control with a capillary across the coil face that trips to protect a water or steam coil from freezing
French drain: Perforated pipe in a gravel trench wrapped in filter fabric, sloped to an outlet, that collects water from the soil [https://anvilfield.com/field-guides/glossary/french-drain/]
Frequency match: Incoming set brought to bus frequency, set slightly high so it lands picking up load
Fresh density: Unit weight of the fresh mix, measured per ASTM C1688, the common acceptance check against the mix-design target [https://anvilfield.com/field-guides/glossary/fresh-density/]
Friable: Material that can be crumbled or powdered by hand pressure when dry, releasing fibers easily; the higher-hazard category
Friction rate: The design pressure drop per 100 ft of duct, ASP times 100 divided by TEL, in in. wg per 100 ft
Fringe: An hourly benefit amount owed on top of the base rate, payable as bona-fide benefits or as cash
FRL: Filter, regulator, and lubricator assembly at the point of use
Front-loading: Weighting early SOV line items so billing runs ahead of cost early in the job
Frost line: The depth to which ground freezes locally, below which footings should sit to resist heave
Frost line / frost depth: The depth the ground freezes; footings bear below it or are frost-protected
Frost-depth footing: A footing bearing below the local frost line on undisturbed soil so the deck does not heave when the ground freezes [https://anvilfield.com/field-guides/glossary/frost-depth-footing/]
Frosting: Matte gray finish from many microscopic discharge pits, the early stage of shaft-current damage
FRP: Fiberglass-reinforced plastic tray for corrosive environments; nonconductive, needs a separate EGC
FS (safety factor): Factor the design holds the actual bending stress below the modulus of rupture, commonly 1.7 to 2.0
FSK facing: Foil-scrim-kraft laminate on duct wrap that serves as the vapor barrier, installed to the warm side
Ftemp: Ambient temperature correction factor from NEC Table 310.15(B)(1)
FTTH / FTTx: Fiber to the home, and the family of variants (curb, node, building) where fiber stops short of the home
Fuel gas: A flammable gas such as acetylene, propane, or propylene that burns or explodes
Fuel polishing: Recirculating stored fuel through filters and a water separator to remove water, sludge, and microbial growth
Full / structural demolition: Taking the whole structure down, frame and all, to clear the site. The companion building-demolition guide covers it.
Full-depth patch: Permanent repair cut to a sound base, replacing failed base, then rebuilding the asphalt in lifts
Full-depth reclamation (FDR): Pulverizing the full asphalt section and part of the base in place and stabilizing it into a new base course
Full-maintenance vs oil-and-grease: Full-maintenance bundles callbacks, repairs, parts, and testing into the monthly price; oil-and-grease covers only basic upkeep and bills repairs separately
Full-port / standard-port: Bore equal to pipe inside diameter, versus a bore one size smaller that adds pressure drop
Full-pour vs latex porous: Cast impermeable polyurethane that sheds water off, versus permeable latex that drains through
Fully adhered: Membrane glued across the whole sheet with adhesive; generally the highest wind-uplift attachment
Fume hood: An enclosure that protects a worker by drawing air in across its opening and exhausting the contaminated air outside, the primary containment for chemical work
Function: What an element must do, stated as an active verb and a measurable noun, such as support load or resist water
Functional testing: Running a system through its modes to prove what it physically does, not what the graphic says
Functional vs cosmetic damage: Functional damage fractures the mat or harms the roof's function; cosmetic is surface marking only, often policy-excluded
Furnace temperature rise: Supply minus return across a furnace, held inside the nameplate range
Further-loss prevention: The damage the securement keeps from happening, documented as the justification for the covered emergency expense
Fused vs non-fused: Fused has fuses in the switch for overcurrent protection; non-fused is the switch only, with protection upstream
Fusible link: A solder-jointed heat detector holding the detection cable; melts at its rated temperature to actuate the system [https://anvilfield.com/field-guides/glossary/fusible-link/]
Fusion splice: A permanent weld of two fibers by electric arc, typically under 0.1 dB
Fusion splice / closure: Two fibers arc-welded into one, protected and housed in a sealed re-enterable enclosure
FVIR: Flammable vapor ignition resistant, a sealed-chamber gas tank with a flame arrestor screen
FVNR / FVR: Full-voltage non-reversing and full-voltage reversing across-the-line starters
FWS: Facility water system, the dirtier primary building water loop the CDU rejects heat into, treated like an industrial cooling loop [https://anvilfield.com/field-guides/glossary/fws/]
FWS / TCS: Facility water system, the building primary loop, and technology cooling system, the clean secondary loop, separated by the CDU heat exchanger
fy / fu: Specified yield strength and specified tensile strength of the bar, the figures the splice classes are written against
G702 / G703: The AIA application and certificate for payment (summary) and the continuation sheet (line-item detail); two halves of one pay application
Gain: The length a 90 saves by sweeping a radius instead of a sharp corner, subtracted on a measured piece
Gallon per square: Coating applied per 100 square feet of roof, the trade's spread-rate unit
Galvalume: An aluminum-zinc alloy coating on steel, roughly 55 percent aluminum, for corrosion resistance [https://anvilfield.com/field-guides/glossary/galvalume/]
Galvanic / sacrificial system: CP driven by an active-metal anode (Mg, Zn, Al) that corrodes in place, with no external power
Galvanic anode: A sacrificial zinc element tied to the steel that corrodes preferentially and feeds it a small protective current [https://anvilfield.com/field-guides/glossary/galvanic-anode/]
Galvanized scale: Internal rust and mineral buildup that narrows old steel pipe over years, the classic gradual whole-house cause
Galvanized steel: Zinc-coated carbon steel, the standard sheet metal duct material
Gang form: Many panels joined into one rigid unit that is set, stripped, and flown by crane as a single piece for large repeating walls
Gangway: The hinged ramp from shore to a floating dock, whose slope changes with the water level
Gas ballast: An air bleed on an oil-sealed pump that keeps condensable vapor from collecting in the oil
Gas connector and restraint cable: A listed flexible gas connector with a quick-disconnect lets a movable appliance roll out for cleaning; the restraint cable stops it before it strains the gas line
Gas-permeable layer: A bed of clean coarse aggregate under the slab that lets soil gas and the system's suction spread across the footprint
Gas-phase filtration: Chemical media such as activated carbon that adsorbs corrosive gases that MERV filters cannot capture
Gator-style watering bag: A zippered bag that wraps the trunk and weeps a slow soak into the root ball over hours; remove it once watering tapers off
Gauge: Steel sheet thickness; a lower gauge number is thicker steel and holds more pullout [https://anvilfield.com/field-guides/glossary/gauge/]
Gauge rake: An adjustable rake that meters the underlayment to a set depth as it is spread
Gazebo: A free-standing building with a solid roof and often a railed, partly open perimeter
GBP / map pack: Google Business Profile and the top-three local results box it feeds
GEC: Grounding electrode conductor, the connection from the service or source to the grounding electrode system and the earth [https://anvilfield.com/field-guides/glossary/gec/]
GEC / EGC: Grounding electrode conductor to the earth electrodes, and equipment grounding conductor for the fault path
Gel / working time: The short window after dispensing during which the rod can still be set and adjusted
General conditions: The project-level indirect costs of running one job, distinct from company overhead; sometimes also the contract's legal terms
General Duty Clause: OSH Act Section 5(a)(1), the requirement used to cite ergonomic hazards absent a specific standard
General industry vs construction: General industry, OSHA 1910, governs the owner's maintenance access; construction, OSHA 1926, governs the contractor building or re-roofing
General requirements: CSI MasterFormat Division 01: the spec sections for temporary facilities, submittals, quality, scheduling, and closeout
Geocomposite / fin drain: Prefabricated plastic drainage core wrapped in geotextile, a thin vertical alternative to the aggregate trench
Geofence: A virtual boundary around a jobsite that can prompt clock-in and clock-out and stamp where a punch happened
Geogrid: Polymer grid laid between courses and back into the backfill, tying block and soil into one reinforced mass [https://anvilfield.com/field-guides/glossary/geogrid/]
Geotextile: A separation fabric over weak subgrade that keeps soil fines and base stone from migrating into each other [https://anvilfield.com/field-guides/glossary/geotextile/]
Geotextile / geogrid: Fabric that separates stone from soft soil, or grid that reinforces and confines the aggregate
Geotextile filter: Fabric that passes water while holding back soil fines, matched to the subgrade gradation
Geotextile vs geogrid: A geotextile is a closed fabric that separates and filters; a geogrid is an open grid that reinforces by aggregate interlock.
GES: Grounding electrode system, all present electrodes bonded into one system per NEC 250.50
GET: Ground-engaging tools, the cutting edges, bucket teeth, and blades that wear by design and get replaced on a plan
GFCI: Ground-fault circuit interrupter, which trips on small leakage current before a shock becomes fatal [https://anvilfield.com/field-guides/glossary/gfci/]
GFCI / AFCI: Ground-fault (shock) and arc-fault (fire) protective devices in standard receptacle bodies
GFCI / GFI: Ground-fault circuit interrupter, the protection that trips on fault leakage current to protect personnel [https://anvilfield.com/field-guides/glossary/gfci-gfi/]
GFEP: Ground-fault equipment protection, about 30 mA, required on heat trace; not the 5 mA personnel GFCI
GFPE / GFP: Ground-fault protection of equipment, protects gear at much higher currents, not a personnel device [https://anvilfield.com/field-guides/glossary/gfpe-gfp/]
GFRC: Glass fiber-reinforced concrete, a thin architectural composite with alkali-resistant glass fibers
GGI: Gravity grease interceptor, the large in-ground tank sized in gallons of volume
Ghost line: A faint scar or shadow left by a removed marking that can read as a false line
Ghost lines: The faded outline of previous striping used as a layout guide on a restripe
Ghost patch / undocumented jumper: A record row with no jumper, or a live jumper with no row; the two discrepancies an audit exists to reconcile
Ghost voltage: An induced false reading on a de-energized conductor near a live one, common on non-contact pens
Girdling: Bark and cambium gnawed or rubbed all the way around a trunk, which cuts the flow between roots and canopy and kills the plant
Girdling root: A root circling the trunk instead of growing outward, which thickens over years until it strangles the stem [https://anvilfield.com/field-guides/glossary/girdling-root/]
GL: General liability, covering third-party bodily injury and property damage your work causes
Glass beads: Tiny glass spheres dropped onto or mixed into a marking to make it reflect headlights at night
Glass replacement / re-glazing: Removing failed or broken glass and setting new glass that meets or beats the code-required glazing for the location
Glass-compatibility chart: The film manufacturer's chart or calculator that approves a specific film for a specific glass before application
Glassbreak / shock: Acoustic glassbreak hears breaking glass across a room; shock senses impact on the single pane or safe it is mounted to
Glide: The temperature spread of a zeotropic blend at one pressure; use dew point for superheat, bubble point for subcooling
Global stability: Deep-seated failure where a block of soil and the wall slide as one along a slip surface
Gloss level (CPC 1 to 4): The finished shine, from flat (1) to highly polished (4), set by the final resin grit
Glovebag: A single-use sealed bag with built-in gloves fitted around pipe or a fitting for small removals, max ~60 by 60 in, not above 150 degrees F
Glycol: Propylene-glycol-and-water antifreeze that keeps the outdoor loop from freezing
Glycol refractometer: The field tool that reads glycol concentration from a drop of fluid, confirming freeze protection and flagging dilution
Gmax: Surface-hardness number from a drop-impact test; below 200 per ASTM F1936 is the common target
Gmb: Bulk specific gravity of the compacted core or mat, the in-place density (AASHTO T166 / T331) [https://anvilfield.com/field-guides/glossary/gmb/]
Gmm: Theoretical maximum density, the airless density of the mix; in-place density is reported as a percent of it
Gmm (Rice value): Theoretical maximum specific gravity of the loose mix, the zero-void density and the 100 percent reference (AASHTO T209 / ASTM D2041) [https://anvilfield.com/field-guides/glossary/gmm-rice-value/]
Gmm / % Gmm: Theoretical maximum density and in-place density as a percent of it; 100 minus % Gmm is roughly the air voids
Gmm / Gmb: Maximum theoretical (Rice) and bulk specific gravity; air voids come from their ratio
GMP: Guaranteed maximum price, the contractor's capped commitment, with the owner paying the actual cost of the work plus a fee up to the cap.
GNSS / RTK: Satellite positioning with real-time corrections, the basis of GPS machine control
Go-ball / go-devil: Sponge ball run through the line on cleanout to wipe the bore clear of concrete
Good-better-best: The three-option proposal that lets the customer choose which system, not whether to buy
gpf: Gallons per flush, the volume the valve delivers; the WaterSense and code limits are set in gpf.
gpf / gpm: Gallons per flush for a toilet or urinal, gallons per minute for a faucet or showerhead; the units the efficiency limits are written in
GPH / GPM: Gallons per hour, the emitter and drip flow unit; gallons per minute, the spray unit. GPH divided by 60 is GPM [https://anvilfield.com/field-guides/glossary/gph-gpm/]
GPM: Gallons per minute, the water flow rate a balance sets at every coil and circuit to match design [https://anvilfield.com/field-guides/glossary/gpm/]
GPM / GPH: Gallons per minute for spray and rotor flow; gallons per hour for drip emitters
GPM / LPM: Gallons or liters per minute, the coolant flow rate balanced per node against the cold-plate spec [https://anvilfield.com/field-guides/glossary/gpm-lpm/]
GPP (grains per pound): Absolute moisture content of the air, grains of water vapor per pound of dry air
GPR: Ground-penetrating radar, used to locate rebar, cables, conduit, and voids before cutting [https://anvilfield.com/field-guides/glossary/gpr/]
GPS: Position from a base station or corrected signal that ties every IC reading to a location on the mat
GPS / GNSS RTK: Satellite positioning with real-time kinematic corrections from a base to a rover, accurate to about a centimeter, for site and earthwork layout
GPUDirect Storage: A direct DMA path from storage into GPU memory that skips the CPU bounce buffer
Grade beam: A beam spanning between piers or piles, carrying load over weak soil
Grade break: The line where two slopes meet, kept perpendicular to the direction of travel and flush
Grade control: Automatic system that cuts to a reference (string, beam, sonic, or 3D) instead of the old surface
Grain: The direction the fibers lean, which reads as a shade of green and must run the same way across every seam
Grain per gallon (gpg): The common US hardness unit; 1 gpg is about 17.1 ppm as calcium carbonate
grains: Grains of water vapor per pound of dry air, the unit the latent load is figured in
Grains per pound: Moisture content of air by weight, used to size the latent load the DOAS has to remove
Grains per pound (gr/lb): Absolute moisture: grains of water vapor per pound of dry air; the chart and load-calc unit [https://anvilfield.com/field-guides/glossary/grains-per-pound-gr-lb/]
Granular base: Compacted crushed stone over the subgrade for even support and drainage, not for structural thickness
Granules: Mineral granules broadcast into the top coat for walkability, impact, and UV protection
Gravel stop: The metal roof edge, also called a gravel guard, that holds the flood coat and aggregate on the roof
Gravity feed: Filling a horizontal crack with a very low-viscosity resin that sinks in under its own weight
Gray space: The back-of-house support area for the mechanical and electrical plant
Graywater / greywater: Gentler wastewater from lavatories, showers, tubs, and laundry, not toilets or kitchen
GRD: Grilles, registers, and diffusers, the family of air terminal devices at the ends of the duct system
Grease duct: The welded, liquid-tight steel duct carrying grease-laden vapor from the hood to the exhaust fan
Grease interceptor: A tank that catches fats, oils, and grease from a kitchen, a different job from a fixture trap
Grease-duct wrap: A listed insulation blanket around the duct, rated for fire resistance and reduced clearance
Green tag: The AHJ inspection approval that releases the utility to reconnect and set the meter
Grid flexibility: The ability to vary a site's grid draw on demand, by shaving, shifting, shedding, or curtailing, without dropping the critical load
Grind and polish: Cutting the cured topping with progressively finer diamonds to expose the chips and bring the surface to the specified finish
Grooved coupling: A gasketed, segmented housing over a rolled or cut groove, the fast mechanical joint for large steel under AWWA C606
Gross margin: Revenue minus direct cost (labor, material, equipment, subs), as a percent of revenue
Gross vs net margin: Gross is what is left after direct cost; net is what is left after overhead too
Ground improvement: Strengthening or stabilizing weak soil in place so it carries the structure without deep foundations or full excavation
Ground resistance: The resistance from an electrode through the soil to remote earth, in ohms; the output you measure
Ground resistance / earth resistance: Resistance from the electrode system to remote earth, in ohms
Ground ring / counterpoise: A buried conductor encircling the structure, at least 18 in deep, tying all electrodes to a common ground [https://anvilfield.com/field-guides/glossary/ground-ring-counterpoise/]
Ground snow load: The mapped snow weight per square foot on the ground at a location, the basis for the roof load in ASCE 7
Ground-return sensing: A CT on the main bonding jumper that reads returning ground-fault current
Grounded conductor: The neutral, a current-carrying conductor bonded to ground at the service, carrying normal load current back to the source [https://anvilfield.com/field-guides/glossary/grounded-conductor/]
Grounded conductor / neutral: The current-carrying return, identified white or gray (NEC 200.6)
Grounding (earthing): Connecting the system to earth for voltage stabilization, surge and lightning, and a common reference, not for clearing faults
Grounding conductor (EGC): The equipment grounding conductor, a bonding conductor that carries fault current back to the source to trip the breaker, sized from the overcurrent device
Grounding electrode conductor (GEC): The conductor tying the service or source to the grounding electrode system, the only one of the three whose job is the connection to earth [https://anvilfield.com/field-guides/glossary/grounding-electrode-conductor-gec/]
Grounding electrode system (GES): All qualifying electrodes at a building bonded into one earth connection for reference, surge, and lightning
Group / team control: The coordinated mode where in-row units in a zone share a demand signal so they split load instead of fighting
Group A / Group B: A keeps the platform over the chassis (scissor, vertical mast); B reaches beyond it (boom lifts)
Group lockbox: A box holding the isolation keys, with each exposed worker's personal lock on it, so no key comes out until all workers are clear
Grout coat: A matching matrix spread after the first grind to fill the pinholes and voids, cured, then ground back off the field
Grout-filled sleeve: A coupler where bars set in an oversized sleeve are bonded by high-strength grout, common in precast
Grout: cementitious vs epoxy: Cementitious grout (ANSI A118.6 and A118.7) is common and needs sealing; epoxy grout (A118.3) resists stains and chemicals and does not need sealing.
Grow lights: Supplemental lighting on a spectrum, intensity, and photoperiod that gives interior plants the light the room cannot
Grow-your-own: Building technicians through training and apprenticeship rather than hiring already-experienced people from a scarce pool
GRR: Galvanized requiring replacement, galvanized pipe downstream of lead that absorbed and re-releases lead
GT-1: ANSI/SPRI test standard for the wind and load resistance of external gutter systems
Guard / handrail height: 42 in commercial and 36 in residential for guards; 34 to 38 in for handrails, to the right datum
Guard-post attachment: The bolted-and-blocked connection with a hold-down that carries the guard load into the frame; the weak point when a post is only surface-lagged
Guardrail: A passive barrier at the edge that stops a worker reaching the fall, needing no harness or clip-in
Guardrail (guard): The code-required fall barrier at a drop-off over the height threshold, sized for a height, a load, and the infill
Guardrail (height / load / 4-in sphere): A fall barrier, commonly 36 in tall residential, resisting a 200 lbf concentrated load, with infill that blocks a 4 in sphere
Guide: A support that holds the pipe in line but lets it slide along its axis
Guideline 36: ASHRAE's standardized high-performance control sequences for VAV systems and air handlers [https://anvilfield.com/field-guides/glossary/guideline-36/]
Gutter pan: The flat channel between the curb face and the pavement that carries water to the flow line
Guying: Temporary support using angled lines to ground anchors, for larger or heavier trees [https://anvilfield.com/field-guides/glossary/guying/]
GVWR: Gross vehicle weight rating, the maximum loaded weight the manufacturer rates for the vehicle, and a regulatory threshold at 10,001 lb
GVWR / GCWR: Gross vehicle weight rating for a single unit, gross combination weight rating for a truck plus trailer, set by the manufacturer
GWP: Global warming potential, a refrigerant's climate impact relative to carbon dioxide [https://anvilfield.com/field-guides/glossary/gwp/]
Gypsum board / drywall: A panel of gypsum core wrapped in paper or glass mat, screwed to framing to form the interior face of walls and ceilings
H friction: Friction head lost in the suction piping, strainer, and valve before the pump inlet, in feet [https://anvilfield.com/field-guides/glossary/h-friction/]
H static: Static height of water above the pump suction in feet; positive on a flooded suction, negative on a suction lift [https://anvilfield.com/field-guides/glossary/h-static/]
H2S: Hydrogen sulfide, the rotten-egg sewer gas that deadens the sense of smell as it reaches deadly concentrations
HAC: Hot-aisle containment, which encloses the hot exhaust aisle and ducts it to the return, keeping the room cool
HACCP cold-holding temperature: The food-safety control point: cold TCS food held at or below the food-code limit, commonly 41°F, monitored and logged, with the danger zone running 41°F to 135°F
Hail vs wind damage: Hail leaves random bruises and granule loss; wind leaves directional creased, torn, lifted, or missing shingles
Half-cell potential: The steel's electrical potential against a reference cell, mapped to find where corrosion is active, per ASTM C876 [https://anvilfield.com/field-guides/glossary/half-cell-potential/]
Half-warm / cold mix: Asphalt produced lower still (half-warm) or at ambient with emulsion or cutback (cold); separate products
Halocarbon vs inert gas: Halocarbons (FK-5-1-12, HFC-227ea) put fire out mainly by absorbing heat; inert gases (IG-541, IG-55, IG-100) lower oxygen below combustion [https://anvilfield.com/field-guides/glossary/halocarbon-vs-inert-gas/]
Handle tie: Listed accessory joining two single-pole breaker handles so they switch together
Handrail: The graspable rail on stairs and ramps, set at 34 to 38 inches, sized for the hand and for the catch of a stumble
Handwork / luting: Hand-placed asphalt where the paver cannot reach, and truing its surface with the lute or rake
Hanger wire: The wire suspending the grid from the structure, commonly 12 ga, attached to structure only and hung plumb
Hard / extra-hard usage: The flexible-cord ratings required for jobsite cords, marked on the jacket, like SOOW or SJTW
Hard clash: Two solid elements occupying the same physical space, such as a pipe through a beam
Hard-set vs pressure-sensitive: Permanent curing adhesive versus a tacky film that grips and can release
Hardened-off: Stock acclimated to outdoor conditions before planting, so it transitions into the bed instead of shocking or burning
Hardiness zone: A USDA map band based on average annual coldest winter temperature, used to tell whether a perennial survives local winters
Hardness (gpg / ppm): Dissolved calcium and magnesium; 1 grain per gallon is about 17.1 ppm as calcium carbonate
Hardscape drainage: Moving water off the surface and out from behind and under a patio, walkway, or wall, so it is never trapped
Harmonic order: Whole-number multiple of the fundamental; the 5th is 300 Hz on a 60 Hz system
Hartford loop: A return connection just below the boiler water line that limits water loss if the return leaks
Harvest cycle: The phase where a cuber warms the evaporator to release the frozen ice into the bin, between freeze cycles
Haul route: The defined path vehicles take through the site, often one-way, sized for the largest vehicle that uses it
HAZ: Heat-affected zone, the base metal beside the weld whose properties the cooling rate changes
Hazard assessment: The walk of a task to find the hazard to each body part and select PPE against it, required and, in general industry, documented
Hazard classification: NFPA 13 grouping of a space by contents (Light, Ordinary 1-2, Extra 1-2) that sets the design density
Hazardous (classified) location: An area where flammable gas, combustible dust, or ignitable fibers may be present in enough quantity to make electrical equipment an ignition risk
Hazardous energy: Any energy that can injure on release: electrical, mechanical, hydraulic, pneumatic, thermal, chemical, or gravity
Hazmat survey: The pre-demolition inspection for asbestos, lead, PCBs, mercury, and other regulated materials, required before demolition. [https://anvilfield.com/field-guides/glossary/hazmat-survey/]
HDD / microtrenching: Horizontal directional drilling steers a bore underground; microtrenching cuts a narrow shallow slot in pavement
HDPE: High-density polyethylene, the fused jointless pipe pulled in during bursting
Head: Pressure expressed as the height of a water column; 10 ft of head is about 4.3 psi at the bottom [https://anvilfield.com/field-guides/glossary/head/]
Head (feet): The energy the pump adds, expressed in feet of water; about 2.31 feet equals 1 psi for cold water
Head box: A reservoir built above the gap on the pour side that creates hydraulic head to drive grout across
Head entrapment / 3.5 to 9 inch rule: A bounded opening within reach must be 3.5 in or smaller, or 9 in or larger; the range between traps a head and is a strangulation hazard
Head lap / side lap: The horizontal and vertical overlaps between underlayment courses, printed as lines on most sheets
Head-to-head coverage: Spacing heads so each throws to the next, giving close to 100 percent overlap
Headlap: The overlap of a slate by the course two above it, giving three thicknesses at every line; 3 in standard
Headlap and exposure: Headlap is how far a course laps the one below; exposure is the part of the tile left to the weather; more lap means less exposure
Headroom: The margin held between the capped load and the installed capacity, the buffer the spike rises into [https://anvilfield.com/field-guides/glossary/headroom/]
Healthcare HVAC: Ventilation and air conditioning that performs infection control in a hospital, treating the room's air as a clinical device
Heat anticipator: An adjustment on older stats that shortens the heat cycle to hold temperature steadier
Heat exchanger: The sealed metal chamber that transfers heat while keeping flue gas out of the air [https://anvilfield.com/field-guides/glossary/heat-exchanger/]
Heat exhaustion: Early heat illness: heavy sweating, dizziness, nausea, headache, fast pulse, still mentally alert
Heat flux: Snow-melt design load in Btu/hr per square foot, the heat the surface must deliver
Heat fusion: Welding HDPE pipe into one continuous line with a heater plate or an electrofusion coil [https://anvilfield.com/field-guides/glossary/heat-fusion/]
Heat index: Apparent temperature from air temperature plus humidity, in °F, available from weather apps and the OSHA-NIOSH Heat Safety Tool
Heat input: Energy delivered per unit length of weld, kJ/in or kJ/mm, controlling cooling rate
Heat of adsorption: Heat released into the process air as vapor adsorbs, why the dry air leaves warm
Heat of hydration: The heat released as cement reacts with water, which accumulates in a thick element
Heat or lot number: The production-run identifier used for traceability and claims
Heat pump (hybrid): An electric tank that moves heat from the air into the water at two to four times resistance efficiency
Heat pump / COP: Equipment that raises the temperature of recovered heat using electricity; COP is heat delivered divided by electricity consumed
Heat recovery: A VRF that can heat some zones and cool others at once, moving heat between them off one outdoor unit
Heat stroke: Medical emergency: confusion, slurred speech, collapse, high core temperature; call 911 and cool immediately
Heat trace: Electric heating cable run under the insulation to replace lost heat and actually prevent freezing [https://anvilfield.com/field-guides/glossary/heat-trace/]
Heat-stress wearable: A device reading heart rate and estimating core-temperature strain to flag heat illness early
Heat-trap nipple: A fitting at the top of a water heater that stops convective heat loss and can scale or jam, choking the hot side
Heating airflow: The airflow a reheat box delivers in heating, a separate setpoint from the cooling minimum on a dual-max sequence
Heating value: Heat per cubic foot of gas, about 1,000 BTU/ft3 for natural gas, near 2,500 for propane
Heave: Upward movement from soil swelling, usually expansive clay taking on moisture, the opposite of settlement [https://anvilfield.com/field-guides/glossary/heave/]
Heavier than air: Specific gravity near 1.5, so propane sinks and pools low instead of rising
HECP: Hydraulic erosion control product, the ECTC family from plain mulch up to BFM
hef (embedment): Effective embedment depth, how far the anchor reaches into the concrete, in inches or mm
Helical pier / screw pile: A steel shaft with one or more helical plates, screwed into soil until the plates bear in firm strata, carrying load in compression or tension.
Helical plate (helix): The steel plate welded to the shaft at a true pitch that bears on the soil; its diameter and number set the bearing area and the capacity.
HEPA: High Efficiency Particulate Air, 99.97 percent capture at 0.3 micron, the most penetrating particle size [https://anvilfield.com/field-guides/glossary/hepa/]
HEPA / ULPA: High-efficiency filters; HEPA 99.97% at 0.3 micron, ULPA 99.999% or better near 0.12 micron
HEPA air scrubber / AFD: Air filtration device with a HEPA filter that lowers airborne spores and, ducted outside, creates negative pressure
Hermetic / semi-hermetic / open: Motor sealed in a welded shell, bolted serviceable housing, or external with a shaft seal
Herringbone: A 45 or 90 degree zigzag pattern that resists vehicular creep; recommended for driveways and streets
HET: High-efficiency toilet, flushing at 1.28 gpf or less, the WaterSense threshold and about 20 percent below the federal maximum
HFC / HFO: Hydrofluorocarbon (high GWP, A1) and hydrofluoroolefin (low GWP, often A2L)
HGI / grease trap: Hydromechanical grease interceptor, the small flow-rated unit sized in gallons per minute
Hierarchy of controls: The ranking of protections strongest first: eliminate, substitute, engineer, administrative, PPE; a wearable sits at or below PPE [https://anvilfield.com/field-guides/glossary/hierarchy-of-controls/]
Hierarchy of fall protection: The ranking of systems from most to least effective: eliminate, then passive guardrails, then travel restraint, then fall arrest last
High leg (wild leg): On a four-wire delta, the line that reads about 208 volts to neutral; must be identified and kept off 120-volt loads
High side / low side: The high-pressure half from compressor discharge to the metering device, and the low-pressure half from the metering device to the compressor suction
High-build immersion lining / DFT: A thick, dense, product-matched film; DFT is its cured dry film thickness in mils
High-heat procedures: Extra controls above an upper trigger temperature: more water and rest, closer watching, pre-shift warning
High-intensity (luminous): Gas heater with a glowing ceramic emitter at a high surface temperature, commonly near 1800°F, for spot heat
High-leg / wild-leg: The higher-to-ground phase of a 4-wire delta, marked orange (110.15)
High-level alarm: The audible, visual, and remote alert that trips above the lag-pump level when the pumps are not keeping up, before the wet well overflows
High-limit: The safety control above the operating control that cuts the burner on excess temperature or pressure, often manual-reset
High-temp underlayment: A tile-rated membrane that holds up to the heat tile traps against the deck, where a standard ice-and-water shield would flow
High-voltage spark test: A charged brush swept over a dry, exposed membrane that sparks to ground at a pinhole; for bare membranes only
High-water alarm: A float-triggered horn or alert that sounds when water rises past the primary's normal level
Hinge: The band of uncut wood left between the notch and the back cut that steers and holds the falling tree
Hitch: How the sling attaches to the load (vertical, choker, or basket), each with a different rated capacity
HM: Horizontal multiplier, for the distance of the hands from the body
HMA: Hot mix asphalt, the conventional mix produced commonly around 300 to 350°F
HMA / hot mix asphalt: Asphalt produced and placed hot, the standard product of an asphalt plant
HMA / WMA: Hot-mix asphalt and warm-mix asphalt; WMA compacts at lower temperatures and extends the window in the cold
HOA: Hand-off-auto switch; in hand the device runs regardless of the BMS, bypassing the automation, the classic commissioning find
Hold point: A mandatory stop where work cannot proceed until the inspection is signed off [https://anvilfield.com/field-guides/glossary/hold-point/]
Hold time: How long the test pressure is maintained; a code minimum around 10 minutes for examination, often 2 hours or more for spec acceptance
Holding strength: The tested load an attachment resists in slide and pull-out, used with a safety factor in the layout
Hole / floor opening: A gap of 2 inches or more in its least dimension in a walking or working surface
Hole balance: The ratio of the weakest sampling hole's flow to the strongest, kept above a floor so no hole is starved
Holiday / pinhole: A pinhole, void, or bare spot in the film where the substrate is exposed, found by spark or sponge detection
Holiday detection: Electrical testing, wet sponge or high-voltage spark, that finds pinholes and bare spots in the film
Hollowcore: A flat floor or roof plank with voids run through it to cut weight, joined by grouted keyways
Home run / slack / rack dress: The three parts of one drop's installed length: the routed run, the service loop, and the run up the cabinet to the port
Honeycomb: Voided, stone-exposed concrete where the mortar never filled between the coarse aggregate
Hook-and-loop: Reusable fabric strap, VELCRO ONE-WRAP the common brand, that binds a bundle without crushing it
Horizontal cabling: The run from the telecom room to the work-area outlet, limited to 90 m of permanent link
Horizontal lifeline (HLL): A cable or rail between anchors with an energy absorber that lets a worker stay tied off while moving along the roof
Horizontal manager: A 1U or 2U finger duct or brush panel that carries cable side to side at the patch panels
Horizontal storm drain: The sloped horizontal pipe that collects conductors and carries the combined flow toward the building storm sewer
Horizontal vs vertical carrier: Horizontal carriers tie the waste into a horizontal branch; vertical carriers turn it down into a stack on stacked floors
HOS: Hours of service, the federal limits on driving and on-duty time in 49 CFR Part 395
Hose whip: A concrete pump end hose lashing out when a blockage clears under pressure
Host plant: The specific foliage a larva eats, such as milkweed for monarch caterpillars; usually native and species-specific
Hot (ungrounded): The energized conductor from the breaker; lands on the brass screw
Hot / warm / cold: The tiers from fastest and most expensive (hot flash) to cheapest and slowest (cold object or archive)
Hot joint / cold joint: A joint made hot against hot (echelon) versus a new lane paved against a cooled, cured edge
Hot site: A fully running mirror with continuous replication and near-instant failover
Hot surface igniter: The glow bar that heats to incandescence and lights the burners directly
Hot weather concreting: Placing and protecting concrete when high air temperature, low humidity, wind, and sun speed up evaporation and hydration, per ACI 305
Hot work: Any operation producing sparks, flame, or heat that can ignite combustibles, such as welding, cutting, grinding, brazing, or torch work
Hot work permit: The authorization and checklist that controls welding, cutting, and other spark- or flame-producing work
Hot-air weld: A seam fused by hot air and roller pressure, melting the two thermoplastic sheets into one
Hot-gas bypass: A valve that routes hot discharge gas back to the low side to fake a load and hold flow off the surge line at very low load, at an energy penalty
Hot-mix asphalt (HMA): Asphalt and aggregate mixed and laid hot, the standard driveway mat; also called blacktop or bituminous concrete
Hour meter / engine hours: The running-time counter on a machine that triggers the service interval, the equivalent of the odometer on a truck
Hourglass / 2 to 1 ratio: A sealant bead about twice as wide as deep, thinned in the middle so it stretches without peeling
Housekeeping pad: Raised concrete pad the equipment or its isolators sit on; a mounting, not an isolator
HPC / low-permeability concrete: High-performance deck concrete with a low water-cement ratio and silica fume, designed to keep chloride out
HR / S / RD: Home run, slack, and rack dress, the three parts of one drop's installed length in feet
HRWR / superplasticizer: High-range water reducer, ASTM C494 Type F or G, cutting water at least 12 percent or giving high flow [https://anvilfield.com/field-guides/glossary/hrwr-superplasticizer/]
HSG: Hydrologic soil group A to D, ranking native soil infiltration from fast to tight
Human-in-the-loop: An arrangement where the robot runs the structured task and a person sets it up, supervises it, checks quality, and handles every exception
Humidity ratio: The actual mass of water vapor per pound of dry air, in grains or pounds; 7,000 grains equal one pound
HVAC re-contamination: Soot and odor left in the ductwork blowing back across cleaned rooms when the system restarts
HVDC / rack DC power: Distributing direct current at higher voltage, here 400 V or 800 V class, to a rack busbar rather than AC to per-server supplies
Hybrid cable: A single jacketed line bundling optical fiber for signal and copper conductors for DC power up to the RRUs
Hydration: The chemical reaction between cement and water that hardens concrete; it needs water to continue
Hydraulic calculation: The pipe-sizing method that proves the remote heads get the required density at the available supply pressure
Hydraulic head (dh): Extra depth above the overflow inlet needed to pass the design flow
Hydro jetting: Cleaning the pipe with high-pressure water from a nozzle
Hydrodemolition: High-pressure water removal of deteriorated concrete that leaves the rebar and sound concrete intact without micro-cracking
Hydrogen sulfide (H2S): The rotten-egg gas in sewer gas, toxic at high concentration and deadens the sense of smell as it climbs
Hydromulch: The hydraulic mulch in the slurry; also a mulch-only spray for erosion cover
Hydronic: Heating by circulating hot water rather than steam
Hydrophilic / bentonite: Swelling waterstops that expand on contact with water to seal a cold joint
Hydropneumatic tank: A pressure tank with an air cushion that absorbs demand swings on a constant-speed booster so the pump cycles less
Hydroseeding / hydraulic seeding: Seeding done as a sprayed slurry of seed, mulch, tackifier, fertilizer, and water
Hydrostatic head: The pressure standing water exerts on the wall, growing about 0.43 psi per foot of depth [https://anvilfield.com/field-guides/glossary/hydrostatic-head/]
Hydrostatic pressure: The push of standing water against a wall, growing with depth, which can double or triple the wall's load
Hydrostatic relief valve / uplift: Hydrostatic uplift is groundwater pressure pushing up under an empty shell; the relief valve, in the main-drain sump over gravel, lets that water into the pool to equalize so the shell does not float.
Hydrostatic test: Periodic pressure test of the cylinder shell on an interval set by NFPA 10 [https://anvilfield.com/field-guides/glossary/hydrostatic-test/]
Hydrostatic vs hydrokinetic: Hydrostatic seams hold back standing water; hydrokinetic roofs only shed water on a slope
Hydrostatic vs pneumatic test: Pressure test with water (safe, the default) versus with gas (stored-energy hazard, the exception)
Hydroxyl vs ozone: Hydroxyl generators are generally safe in occupied spaces; ozone is a respiratory hazard, unoccupied only
Hydrozone: A group of plants with similar water needs placed together so one irrigation schedule suits them all [https://anvilfield.com/field-guides/glossary/hydrozone/]
Hygroscopic: Strongly attracting and holding water; the property that makes a material a desiccant
Hyperbola: The inverted-U reflection a round target makes on a GPR profile; the peak sits over the target and gives its depth
Hyperscale: A very large, standardized, self-built facility run by a cloud or platform operator
Hyperscale line: The industry's rough threshold for hyperscale, commonly around 100 MW and up
I: Design rainfall intensity, in inches per hour, from the code map or NOAA for the site
I alarm: Total current with all appliances firing, at the installed candela settings, in amps
I standby: Total current the system draws at rest, powering the panel and polling devices, in amps
I_FLA: Transformer secondary full-load current in amps
IAQ investigation: A structured search for the cause of an air complaint, working from the people and the building to a cause before testing
IAQ monitoring vs investigation: Monitoring is continuous, real-time measurement that flags when air is bad; an investigation is a one-time hunt that diagnoses the cause of a complaint
IBN: Isolated bonding network, insulated but still bonded to the building ground at one controlled point, not a separate earth
IBT: Intersystem bonding termination, the shared bonding point for telecom, CATV, and satellite per 250.94
Ice and water shield: Self-adhered waterproof membrane at eaves, valleys, and penetrations that seals around the nails through it [https://anvilfield.com/field-guides/glossary/ice-and-water-shield/]
Ice dam: A ridge of ice at the cold eave that backs meltwater up under the shingles into the building [https://anvilfield.com/field-guides/glossary/ice-dam/]
Ice jacking: Ice freezing around a piling and lifting it as the water rises, ratcheting the piling out of the ground over winters
ICF: Insulating concrete form, a stay-in-place foam form that becomes the wall's permanent insulation and finish substrate
ICMV: Intelligent compaction measurement value, a relative stiffness response from the drum accelerometer that varies by system and is not a density number
ICP: Industrial control panel: the enclosure plus the power circuit plus the control circuit
ICRA: Infection control risk assessment, the required process for containing construction dust and protecting patients during work
IDC: Initiating device circuit, a conventional input circuit reporting by zone
Identifier: The unique, hierarchical string naming an element from building down to port, the same string carried on the label and in the records
IDLH: Immediately dangerous to life or health; requires SCBA or supplied air, never a cartridge [https://anvilfield.com/field-guides/glossary/idlh/]
Idling: Holding the slab at a low warm setpoint so it responds fast when snow falls
IEC 60309: The pin-and-sleeve locking input connector for higher-amp three-phase strips
IEC colors: Brown, black, grey phases, blue neutral, green-yellow ground, the international set
IEEE 1584: The IEEE guide that calculates incident energy and the arc-flash boundary; the calculation method, not the safety rules
IEEE 48 class: The termination class, 1 through 3, set by whether it controls stress, insulates externally, and seals against the environment
IEP: Indoor environmental professional, the independent industrial hygienist or consultant who assesses and clears without a stake in the remediation
IG (isolated ground): Orange device with a green triangle whose ground terminal is insulated from the strap
IG / IGR: Isolated ground, and isolated ground receptacle, the orange triangle-marked device
IG-541 / FK-5-1-12: IG-541 is an inert nitrogen, argon, and carbon dioxide blend; FK-5-1-12 is a low-GWP fluoroketone halocarbon
IGU (insulated glass unit): Two or more panes with a perimeter spacer and a sealed, usually argon-filled cavity; fails by edge-seal failure and fogging.
IGU / seal failure / fogging: Insulated glass unit, two or more lites sealed around a spacer; when the edge seal fails the cavity fogs and the unit is replaced whole
IGU seal warranty: The glass maker's warranty on an insulated unit's edge seal, which aftermarket film can void; confirm before applying
IGV: Inlet guide vanes, a ring of adjustable vanes at the impeller eye that modulate capacity by pre-swirling the entering refrigerant
IICRC S500: The ANSI standard of care for water damage restoration, covering categories, classes, and drying
IICRC S520: The ANSI/IICRC procedural standard for professional mold remediation
IIPP: Injury and illness prevention program, the written safety program; required by Cal/OSHA and some other state plans
Illuminance: Light arriving on a surface, read horizontal at the work plane or vertical at the rack face
Immersion: The whole server submerged in dielectric fluid, single-phase or two-phase
Immersion service: Constant submersion in the stored product, the harshest coating exposure, demanding a product-matched lining
Immobilizer / telematics: A device that blocks the engine from starting without a code or fob, and the GPS system that tracks location and alerts on movement
Impact / tilt indicator: A shock or lean sensor on the crate that turns red when a threshold is exceeded in transit
Impact vs vibratory hammer: A hammer that drives with discrete blows and a blow count, versus one that shakes the pile in with no blow count
Impairment: Any condition where a fire protection system is out of service, requiring tagging, notification, and compensating measures [https://anvilfield.com/field-guides/glossary/impairment/]
Impairment coordinator: The person who authorizes an impairment, makes the notifications, ensures compensating measures, and confirms restoration
Impairment tag: A tag posted at the system control valve and fire department connection showing the system is out of service
Impalement protection: Rated caps or troughs on protruding rebar that stop the bar from penetrating on a fall
Impedance / internal resistance / ohmic value: The opposition to current in a cell; a rising value is the leading aging indicator
Impedance / ohmic value: The cell's internal resistance, conductance, or impedance, trended against a baseline to predict a weak cell
Implosion: Using engineered explosives to drop a structure in place, a rare specialist method.
Impressed current (ICCP): CP driven by a rectifier that forces DC from inert anodes, used for large, bare, or high-current structures
In: Nominal discharge current, the 8/20 microsecond surge current the SPD survives repeatedly and stays functional
In / Imax: Nominal discharge current (repeated, durability) and maximum single-event surge current
in per 10 ft: Straightedge-style levelness tolerance, the allowed gap in a length, used for finished access floors, not an F-number
in w.c. (in wg): Inches of water column, the low-pressure gas unit, about 27.7 in w.c. per psi
in wg / in. w.c.: Inches of water column, the test pressure unit; 1 in wg is about 249 Pa
In-phase monitor: Open-transition control that transfers at the moment the two sources are near synchronized, to protect motors
In-plug fuse: The small fuse in the male plug of a light string that blows when the series run is overloaded
In-row / close-coupled: A cooling unit set in the row between cabinets, drawing hot-aisle return and supplying the cold aisle over a short air path [https://anvilfield.com/field-guides/glossary/in-row-close-coupled/]
In-situ RH: Relative humidity measured by an ASTM F2170 probe set into the slab, reported in percent
in. w.c. / in. wg: Inches of water column, the unit for building and duct pressure; about 249 Pa per inch [https://anvilfield.com/field-guides/glossary/in-w-c-in-wg/]
in. wg / in. w.c.: Inches of water column, the field unit for static pressure; 1 in. wg is about 249 Pa [https://anvilfield.com/field-guides/glossary/in-wg-in-w-c/]
Incentivized review: A review obtained by offering something in exchange; offering compensation conditioned on a particular sentiment is prohibited under the FTC rule
Incident: An unplanned event that caused or could have caused injury, illness, or property damage; OSHA prefers it over accident [https://anvilfield.com/field-guides/glossary/incident/]
Incident commander (IC): The one named person who runs the response, owns the decisions and tempo, and coordinates rather than performing the hands-on repair
Incident energy: Arc-flash thermal exposure in calories per square centimeter, the basis for arc-rated PPE selection [https://anvilfield.com/field-guides/glossary/incident-energy/]
Incident energy (cal/cm2): Thermal energy a worker would receive at the working distance from an arc, in calories per square centimeter; what arc energy reduction lowers [https://anvilfield.com/field-guides/glossary/incident-energy-cal-cm2/]
Incipient / ring / halo anode: New corrosion forming in the parent concrete around a patch as the clean repair turns the surroundings anodic
Incipient anode: New corrosion starting in old concrete just outside a patch repair, the ring or halo effect
Incipient anode / halo effect: New corrosion in the old concrete ringing a fresh patch as the clean repair turns the surrounding contaminated steel anodic
Incipient stage: The early, small, contained phase of a fire that a portable extinguisher can address
Included bark: Bark pinched inside a union as stems grow, leaving a weak seam with no real wood connection
Indemnity / GIA: The general indemnity agreement; you, your company, and often your spouse repay the surety for any loss
Independent vertical lifeline / rope grab: The separate rope on its own anchor that protects the worker, and the device that rides it and locks on a fall
Index circuit: The worst, highest-resistance, usually farthest path that the pump and balance are set to
Index outlet: The outlet reading the lowest percentage of design, left wide open as the reference for proportional balancing
Indirect: A tank with a coil heated by the building's boiler, with no burner or element of its own
Indirect evaporative (IEC): Cools the supply air through a heat exchanger; no moisture added to the space
Indirect waste: A drain that empties into an open receptor through an air gap or air break, not connected directly to the drainage system
Indirect waste / air gap: Discharge through an open gap into a receptor so waste cannot siphon back
Indirect waste and air gap: A food-equipment drain that ends short of a floor sink, leaving an open vertical gap so a sewer backup cannot reach food equipment
Indirect-fired: Burner fires into a heat exchanger; clean supply air, lower efficiency
Indoor head: The indoor unit that hangs in the room; also called the air handler or evaporator
Inducer: The small blower that pulls combustion air and pushes flue gas out the vent
Induction ratio: The volume of room air induced across the coil per unit of primary air, commonly about 3 to 5 to 1
Industrial hygienist: A professional trained in environmental health and exposure, brought in for health, sampling, and litigation questions
Industrial protective coating: A multi-coat film applied to steel or concrete to keep corrosion off the substrate over its service life
Inert / simple asphyxiant: A gas such as argon, nitrogen, or carbon dioxide that displaces breathing oxygen and suffocates without warning
Inertia base: A concrete-filled steel frame under the pump and baseplate that adds mass to damp vibration and steady the isolators [https://anvilfield.com/field-guides/glossary/inertia-base/]
Infant mortality / bathtub curve: The high early-life failure rate at the front of the bathtub curve, the failures burn-in is meant to catch
Infill: Granular sand or coated sand brushed into the fibers to add ballast, stand the blades up, and protect the backing [https://anvilfield.com/field-guides/glossary/infill/]
Infiltration / air curtain: Warm moist air leaking in through openings, and the sheet of air across a doorway that resists it.
Infiltration / exfiltration: Uncontrolled air leaking in through, or out through, the building envelope
Infiltration rate: How fast water moves into the soil or through the surface, in inches or millimeters per hour [https://anvilfield.com/field-guides/glossary/infiltration-rate/]
Infinite bus: The conservative assumption of a zero-impedance utility source, used for worst-case fault current
Infrared / radiant: Heat carried as infrared energy that warms surfaces and people directly, not the air
Infrared thermography: Reading surface heat with a thermal camera to find hot connections, bearing heat, and failed steam traps
Infrared thermometer: Reads surface temperature at a distance; fast for scanning, but affected by emissivity and reads the surface, not the refrigerant inside
Inherent reversing (Type A): The operator's built-in sensor that detects an obstruction by force or current and reverses the gate
inHg (inches of mercury): Rough-vacuum unit; atmospheric is about 29.92 inHg, and house vacuum reads in this range
Inhibited glycol: HVAC glycol carrying a corrosion-inhibitor and acid-buffer package; the only kind that belongs in a hydronic loop
Inhibitor residual: The amount of active corrosion inhibitor left in the water, tested against the vendor's target range
Initial curing: The first 24 to 48 hours on site, held in a controlled temperature range under ASTM C31 with moisture loss prevented
Initial vs aged: Initial is the fresh value; aged is measured after three years of exposure and is what codes require
Initiation device: The single switch that starts rapid shutdown, located where a responder can reach it
Inland marine: Coverage for tools, equipment, and material away from a fixed location
Inland marine / equipment floater: The insurance line that typically covers tools and mobile equipment on a jobsite, with a per-claim deductible the owner pays first
Inlet / intake air: The air entering the front of the IT equipment in the cold aisle, where the envelope is measured
Inrush: The brief startup surge a motor draws, several times running current, caught with an inrush function
Inrush / LRA: Locked-rotor current, the surge a motor draws at start, commonly 6 to 8 times full-load amps
Insertion loss: The noise reduction a silencer or barrier provides, the difference with and without it
Inspection and test plan (ITP): The document listing, per activity, what is inspected or tested, when, to what criteria, by whom, the record, and the hold or witness point [https://anvilfield.com/field-guides/glossary/inspection-and-test-plan-itp/]
Insulated metal panel (IMP): A panel of two steel skins bonded to a foam core that is both the insulation and the vapor barrier.
Insulating transformer: The factory form of a buck-boost, with separate windings, before it is field-connected as an autotransformer
Insulation resistance: DC megger reading of how well the insulation resists leakage to ground and between phases, trended over time
Insulation resistance (IR): The megohmmeter reading across insulation, phase-to-phase and phase-to-ground, recorded with temperature and humidity [https://anvilfield.com/field-guides/glossary/insulation-resistance-ir/]
Intake: Low vents at the eave or soffit that bring outside air in
Integral color: Pigment batched into the wet concrete, coloring the slab through its full depth [https://anvilfield.com/field-guides/glossary/integral-color/]
Integral trap: A trap built into the fixture, as in a water closet, exempting it from a separate trap
Integrated economizer: An economizer that runs at the same time as mechanical cooling so partial free cooling is not wasted [https://anvilfield.com/field-guides/glossary/integrated-economizer/]
Integrated systems test (IST): The commissioning test where the plant rides a simulated failure at load without dropping the critical bus; its signoff is the centerpiece of a data center turnover packet
Integrity test: An ELD survey run to verify a new or repaired membrane is breach-free before it is covered or accepted
Integrity testing / CSL: Post-pour tests for buried defects, including crosshole sonic logging (CSL), thermal integrity profiling, and sonic or pulse echo
Intelligent / managed: A networked strip with metering, switching, and sensors reported to DCIM
Intelligent compaction (IC): Rolling with a vibratory roller equipped with GPS, a drum accelerometer, a temperature sensor, a real-time display, and data logging that maps the work
Intensive: Deep media (6 in and up), shrubs to small trees, high load (often 50 to 150+ psf), garden-level maintenance
Intercom: A two-way voice link between fixed points, such as a door station and a staff position, or room to room
Interconnect: A direct patch from active equipment to a distribution panel; cheaper than a cross-connect but every change touches live gear
Interconnection / point of common coupling: Where the utility's system meets the customer's, the demarcation between grid and site
Interconnection queue: The ordered line of projects waiting for the utility or grid operator to study and approve a connection to the grid [https://anvilfield.com/field-guides/glossary/interconnection-queue/]
Interconnection timeline: The time from queue entry through study and upgrades to actual energization, commonly years for a large load
Interior / selective demolition: Removing a building's finishes and non-structural elements down to the structure for a renovation or fit-out, while protecting what stays. Also called strip-out or soft strip.
Interior stain / drip: Where the water shows inside, after traveling along the deck and structure
Interlayment: The 18 in No. 30 felt strip laid over each course of shakes as a baffle against wind-driven water; shakes only, not shingles
Interlock / isolation: An automatic action on a leak alarm that closes a valve, shuts a CDU, or stops a pump to cut the source
Interlock kit: A listed sliding plate on the panel that mechanically prevents the main and generator breakers from being on at the same time
Intermix beads: Glass beads blended into the material so reflectivity holds as the surface wears
Internal curing: Hydration fed by water released from the saturated aggregate, reducing early-age cracking
Internal rental rate: The rate an owned machine charges a job, so cost lands on the job that used it
Internal traffic control plan (ITCP): The diagram and rules that route construction equipment and workers on foot through the work area so the two stay separated, with marked routes, foot paths, access points, and no-go zones.
Interpass temperature: Joint temperature just before the next pass, the practical heat-input control on multipass welds
Interruptible rate: A utility tariff giving a lower price in exchange for agreeing to curtail load on the utility's signal
Interrupting rating / AIC: Maximum fault current a device can safely open without failing
Intrinsic safety: A protection method that limits circuit energy so low that no spark or hot surface can ignite the atmosphere, even with a fault
Intrusion alarm system: Layered sensors that detect an unauthorized entry, report it at a keypad and a central station, and signal a response; a security system, not life-safety
Intumescent: A thin reactive coating that swells and chars into an insulating foam when heated, for exposed architectural steel [https://anvilfield.com/field-guides/glossary/intumescent/]
Inventory: The documented, photographed, tagged room-by-room record of every item and its condition
Inversion / pull-in-place: The two ways a CIPP liner is installed, turned inside out or dragged in then inflated
Invert: The inside bottom of a pipe; the difference in invert over the run sets the slope
Inverter: The variable-speed compressor that modulates output instead of cycling full on and off
Inward vapor drive: The relentless push of water vapor from the warm humid outside toward the cold dry inside of a freezer.
Ion exchange: Swapping calcium and magnesium on a resin for sodium, the way a softener removes hardness
IOR: Index of refraction, set on the OTDR to convert time to distance
Ip: Component importance factor in ASCE 7, commonly 1.0 for ordinary systems and 1.5 for high-importance ones, which lowers the bracing threshold [https://anvilfield.com/field-guides/glossary/ip/]
IP code (IEC 60529): Two-digit ingress code: first digit solids and dust, second digit water
IP vs analog camera: IP cameras are networked, megapixel, PoE-powered, and the new-build standard; analog and HD-over-coax run over coax and fit coax retrofits
IPC / UPC: The two model plumbing codes, from the ICC and IAPMO; a jurisdiction adopts one, often amended
IPLV / NPLV: Integrated and non-standard part-load value, the AHRI 550/590 metrics for chiller efficiency across the load range [https://anvilfield.com/field-guides/glossary/iplv-nplv/]
IPM: Integrated pest management, the decision process of identify, monitor, threshold, prevent, control, and evaluate [https://anvilfield.com/field-guides/glossary/ipm/]
IR / megger test: Insulation resistance test, named after the megohmmeter that performs it
IR drop: The voltage error in a current-on reading from soil resistance; removed by the instant-off measurement to get the polarized potential
IR window: A permanently installed infrared-transparent port that lets you scan an energized enclosure without opening it
IRI: International roughness index, a measure of pavement smoothness used for ride acceptance and pay [https://anvilfield.com/field-guides/glossary/iri/]
Iron ochre: Orange iron-oxide biofilm that precipitates in drains and clogs the filter and pipe over years
ISA: International Symbol of Accessibility, the wheelchair symbol on the sign and the pavement
ISA severity level: The G1 mild through GX severe classification of how corrosive an environment is, per ANSI/ISA-71.04
Island fixture vent: The loop vent, a hard-piped vent that rises under the counter and loops back below the floor to vent an island sink without an AAV
Islanding: Running disconnected from the utility, the on-site plant holding voltage and frequency on its own
ISO 14644 class: The cleanliness class set by particle count per cubic meter, ISO 1 to 9, lower is cleaner [https://anvilfield.com/field-guides/glossary/iso-14644-class/]
ISO 16890 / ePM: The PM-based global filter standard rating ePM1, ePM2.5, and ePM10 capture
ISO 8573 class: Compressed air purity rating for particulate, water, and oil; lower is cleaner
Isochronous: Constant frequency regardless of load, which needs a load-sharing line to parallel sets
Isochronous / droop: Constant-frequency sharing via active controls, versus frequency that sags with load
Isolated EGC: The separate insulated equipment grounding conductor that serves only the isolated ground terminal, back to the source
Isolation (expansion) joint: A full-depth joint separating flatwork from a fixed object such as a building, pole, or curb
Isolation / expansion joint: A full-depth separation that frees the slab from a fixed restraint, with compressible filler
Isolation efficiency: The percent of the equipment's vibration force the isolator keeps out of the structure
Isolation joint: A full-depth separation that lets the slab move independently of the garage, house, or a fixed object [https://anvilfield.com/field-guides/glossary/isolation-joint/]
Isolation valve: A valve placed to take a component out of a live loop for service without draining the rest of it [https://anvilfield.com/field-guides/glossary/isolation-valve/]
Isometric (iso): A 3D-style drawing of the piping at 30 degrees showing rise, run, and drop in one view
Isothermal humidification: Adding moisture as steam, with no drop in air temperature; energy comes from boiling the water
IST: Integrated systems test, the full-plant test simulating utility failure at load, also called pull-the-plant or black building test [https://anvilfield.com/field-guides/glossary/ist/]
IT equipment energy: Energy delivered to servers, storage, and network gear, measured as close to the gear as the metering allows
ITAD: IT asset disposition, the secure and documented retirement, recycling, and resale of IT assets
ITC: Inspector's test connection, the remote outlet that simulates one open sprinkler for the trip test
ITM: Inspection, testing, and maintenance, the ongoing program under NFPA 72 Chapter 14
J-hook / bridle ring: Non-continuous cable supports; TIA-569 spaces them no more than 1.5 m (5 ft) apart
J1772 / J3400: SAE AC charging connector standard; J3400 standardizes the NACS connector for AC and DC
Jacking force / fpu: The force applied by the jack, commonly near 0.80 of the strand tensile strength, fpu
Jam ratio: Conduit inside diameter over cable outside diameter for three same-size cables; a band near 2.8 to 3.0 risks jamming [https://anvilfield.com/field-guides/glossary/jam-ratio/]
Jet grouting: Using a high-pressure jet to erode and mix soil with grout into columns of soilcrete
JHA / AHA: Job Hazard Analysis, called Activity Hazard Analysis on most federal and large commercial jobs: the written breakdown of a task into steps, hazards, and controls
JHA / JSA / AHA: Job hazard analysis, job safety analysis, or activity hazard analysis; the same process of breaking a task into step, hazard, and control [https://anvilfield.com/field-guides/glossary/jha-jsa-aha/]
JMF: Job mix formula, the approved recipe with target gradation, binder content, and volumetrics, plus tolerance bands [https://anvilfield.com/field-guides/glossary/jmf/]
JMF / job mix formula: The approved production recipe: target gradation, asphalt content, and temperature with tolerances
Jobsite camera system: Cameras plus a software platform that watch a site for security, progress, safety, and the record
Jobsite security: The layered set of measures that protect an open construction site and its tools, materials, and equipment from theft
Jockey / pressure-maintenance pump: A small pump that holds system pressure between events so the main fire pump starts only on a real demand
Jockey pump: A small pressure-maintenance pump that holds system pressure so the fire pump does not start for normal leakage
Joint adhesive: A hot-applied polymer-modified asphalt run on the cold joint face to bond the new lane to the old edge [https://anvilfield.com/field-guides/glossary/joint-adhesive/]
Joint deflection: The maximum angle a bell-and-spigot joint can take and still seal, set by the manufacturer
Joint density: The in-place density at the seam, reported as a percent of Gmm, almost always lower than the adjoining mat
Joint maker / restrictor: The shoe or device on the screed edge that shapes the wedge or pinches the unconfined edge of the first pass [https://anvilfield.com/field-guides/glossary/joint-maker-restrictor/]
Joint profile / tooling: The finished shape of the joint, struck at thumbprint hardness to match the original and shed water
Joint sealant: The elastic material in a joint that keeps water out while letting the joint move
Joist span / DCA 6: The distance a joist spans between supports, sized from the AWC DCA 6 and IRC R507 tables by size, species, and spacing, not by eye
Joukowsky relationship: Surge pressure equals fluid density times wave speed times velocity change, so surge scales with velocity
Journeyman: A tech who has logged the required hours and passed the exam to work independently
JPCP: Jointed plain concrete pavement; no slab steel, crack control by closely spaced joints
JRCP: Jointed reinforced concrete pavement; wider joints with light distributed steel holding mid-panel cracks
Jump / climbing form: A wall form locked, poured, and then raised to the next lift; self-climbing versions carry their own hydraulic jacks
Just-in-time (JIT): Delivering material close to when it is installed instead of stockpiling it, used where there is no room to store
Just-in-time delivery: Scheduling high-value material to arrive close to when it is installed, shrinking the window it sits exposed on site
K: Tension constant, commonly about 0.008 lbf per circular mil for copper and 0.006 for aluminum; verify against the manufacturer and ICEA
k (modulus of subgrade reaction): Soil support stiffness, pressure per unit deflection, in pci; higher and uniform is better
K&T: Knob and tube, the open-air two-wire method using porcelain knobs and tubes, with no ground
K-class: The fire class and portable extinguisher type for cooking oils and fats, governed by NFPA 10
K-factor: A transformer's rating for handling harmonic heating, from K-1 to K-50 under UL 1561 [https://anvilfield.com/field-guides/glossary/k-factor/]
K-rated: A transformer built with extra thermal capacity and a 200 percent neutral for harmonic load
K-rated transformer: A transformer rated to withstand the harmonic heating from nonlinear IT loads, by a K-factor from 1 up
k-value: Modulus of subgrade reaction, the stiffness of the support under the slab, in pci or MPa/m
kA: Kiloamps, thousands of amps, the unit fault current and SCCR are expressed in
kAIC: Thousand amps interrupting capacity, the short-circuit rating of low-voltage gear and overcurrent devices [https://anvilfield.com/field-guides/glossary/kaic/]
Kc: Crop coefficient, the factor that scales ETo to a specific plant type's need
kcmil: Thousands of circular mils of conductor area, the basis for the 0.008 copper and 0.006 aluminum tension constants
kcmil / MCM: Thousand circular mils, the size unit for large conductors; the two terms are identical
Key-up / key-down: Connector orientation relative to the key; sets the left-to-right P1 to P12 fiber numbering and how arrays mate
Keyway: The shaped joint between deck members that is grouted to transfer shear and form the diaphragm
Keyway / offset: The gap between adjacent pieces for the wood to swell, and the side-to-side stagger of those gaps course to course so they do not align
Kick-out flashing: The diverter where a roof eave meets a sidewall that throws roof runoff out of the wall instead of behind the siding
Knob / tube: Porcelain support that holds the wire off framing; porcelain sleeve the wire passes through framing in
Knowledge transfer: Capturing the site-specific and tribal knowledge of experienced staff before they leave, through documentation and mentoring
Known-unknown: A risk you can identify but cannot yet price exactly. Contingency covers these; the unforeseeable unknown-unknowns are covered by a management reserve.
KPI: Key performance indicator: one of the few numbers that move with the health of the business
kVA: Apparent power, the vector sum of kW and kVAR that the conductors and transformer carry [https://anvilfield.com/field-guides/glossary/kva/]
kVA (apparent power): The total the alternator and conductors carry, what the alternator is sized for [https://anvilfield.com/field-guides/glossary/kva-apparent-power/]
kVA / kW: Apparent power and real power; their ratio is the power factor that the UPS rating depends on
kVA / kW / power factor: Apparent power, real power, and their ratio; modern UPS rate at unity
kVA / MVA: Apparent power rating, in thousands or millions of volt-amps; the transformer's size [https://anvilfield.com/field-guides/glossary/kva-mva/]
kVAR: Kilovolt-amperes-reactive, the magnetizing power a capacitor supplies or a motor draws [https://anvilfield.com/field-guides/glossary/kvar/]
kVAR (reactive power): The reactive component a reactive or inductive load bank produces
kVAR_c: Correction reactive power the capacitors must supply to reach the target power factor
kW: Real power, the power that does work, turns the shaft, and makes heat and light [https://anvilfield.com/field-guides/glossary/kw/]
kW (real power): The power the engine produces and the load consumes, what the engine is sized for [https://anvilfield.com/field-guides/glossary/kw-real-power/]
kW / kVA / kVAR: Real power, apparent power, and reactive power; the genset rating ties them through power factor [https://anvilfield.com/field-guides/glossary/kw-kva-kvar/]
kW / ton: Kilowatt of heat load; one ton of cooling is 12,000 BTU per hour, about 3.5 kW
kW per door: The heat a single rear door rejects, set by the water temperature, flow, and the door's capacity curve
kW per rack: Power drawn by a single cabinet, the design number for feeder, busway, and cooling sizing [https://anvilfield.com/field-guides/glossary/kw-per-rack/]
kW per tank: The heat load a tank carries; immersion tanks reach densities far above an air-cooled rack
kW per ton: Electrical power drawn per ton of cooling produced, lower is more efficient
kW rejected: The heat the CDU moves from the secondary loop to the facility water or room air, its capacity at design conditions
kW vs kWh / C-rate: Power (kW) is how fast it delivers, energy (kWh) is how much it holds, and the C-rate is the ratio that sets how hard the battery is run
kW/ton: Total plant power divided by tons of cooling; the plant efficiency metric, lower is better [https://anvilfield.com/field-guides/glossary/kw-ton/]
kWh: Kilowatt-hour, the energy unit PUE is built from; use energy over a period, not a single power reading in kW
kWh / kW: Kilowatt-hours measure energy used; kilowatts measure the rate, and the peak rate is demand
kWh / MWh: Energy stored, kilowatt-hours and megawatt-hours, compared against nameplate capacity
L: One-way conductor length in feet for the run between the two points
L fittings: Equivalent length in feet that elbows, valves, and fittings add to the straight pipe length
L prefix: Locking, twist-lock device with curved blades that rotate to lock, as in L14-30
L, H: Scupper weir length and the head of water over it, in feet
L1 to L5: The common commissioning levels, from factory test through receiving, pre-functional, and functional to the integrated test, with boundaries set by the plan [https://anvilfield.com/field-guides/glossary/l1-to-l5/]
L1, L2, L3: The three supply line conductors landed on the motor terminals
L10 life: The rating life at which 10 percent of a bearing population is expected to have failed
L2L / L2A: Liquid-to-liquid CDU rejecting to facility water through a heat exchanger, or liquid-to-air rejecting to room air through a coil
L70: Hours until LED output fades to 70 percent of initial
L_dev: Developed length of the longest run in feet, including the equivalent length of fittings
LAANC / airspace authorization: The Low Altitude Authorization and Notification Capability, the automated system that grants near real-time approval to fly below the set ceiling in controlled airspace.
Lab pressurization: Holding the lab negative to the corridor by exhausting more air than is supplied, so fumes stay in the lab
Lab-cured (standard-cured): Cylinders cured in ideal moist conditions to judge the mix for acceptance
Labor allowance: A set dollar amount some manufacturers pay toward the labor to install a warrantied replacement [https://anvilfield.com/field-guides/glossary/labor-allowance/]
Labor budget: The hours and production rate the estimate assigned to the work, against which the crew's actual units per labor hour are measured [https://anvilfield.com/field-guides/glossary/labor-budget/]
Labor burden: The payroll taxes, workers' comp, insurance, and benefits added to the bare wage to get the real hourly cost of labor. [https://anvilfield.com/field-guides/glossary/labor-burden/]
Labor efficiency: Actual hours against estimated hours; under 100 percent means the job ran over budget
Labor factor: An adjustment to base install hours for conditions like out-of-sequence work, stacking, congestion, or overtime fatigue
Labor unit: Installed hours assigned to a fixture, a linear foot of pipe, or a fitting [https://anvilfield.com/field-guides/glossary/labor-unit/]
Labor warranty: Your guarantee on your workmanship, commonly 30 to 90 days on repairs and a year on installs
Ladder safety system: Rail or cable with a locking sleeve on a fixed ladder that arrests a fall, replacing the cage
Ladder tray: Two side rails joined by rungs; the most common type, with the best airflow for power cable
Lagging / leading: Lagging is inductive (current behind voltage); leading is over-corrected, capacitive
Lambda factor: ACI 318 modification, less than one, applied to shear and development length for lightweight
Lap splice: Two bars overlapped to transfer force, length set by the class and the development length [https://anvilfield.com/field-guides/glossary/lap-splice/]
Large-format tile (LFT) / lippage: Tile with any edge over 15 in; lippage is the height step between adjacent tile edges, commonly held to about 1/32 in on tight joints.
Laser screed: Self-propelled machine that strikes off to a rotating laser plane with auger, vibrator, and screed plate
Last furnishing: The final date you supplied labor or materials to the project; the recording clock usually runs from it, and punch work may count while warranty work often does not.
Last Planner System: The Lean Construction Institute planning method that pushes the work commitment down to the foremen who do the work
Last Planner System (LPS): The lean planning method of cascading levels: master schedule, phase pull plan, look-ahead, weekly work plan, and PPC learning
Latency: Delay set first by the speed of light in fiber, about 5 microseconds per kilometer one way, the hard limit for replication and training [https://anvilfield.com/field-guides/glossary/latency/]
Latency / tail latency: Time for a packet to cross the fabric; the tail (99th or 99.9th percentile) sets job completion time because the collective waits on the worst path
Latent / evaporation load: The moisture leaving the pool and deck, in pounds of water per hour, that the HVAC must remove; the design driver
Latent heat: The heat absorbed or released in a phase change, about 970 Btu per pound when steam condenses at atmospheric pressure [https://anvilfield.com/field-guides/glossary/latent-heat/]
Latent load: The moisture load, the energy needed to remove water vapor from the air, separate from temperature [https://anvilfield.com/field-guides/glossary/latent-load/]
Latent vs sensible: Latent cooling removes moisture; sensible cooling removes heat without changing moisture
Latent vs sensible load: Latent is the energy in moisture; sensible is the energy in temperature. Humidity control is the latent side
Lateral earth pressure: The sideways force retained soil exerts on a wall, growing with height and worsened by water
Lateral reinstatement: Reopening a service connection with a robotic cutter after a liner sealed over it
Lateral-load connection: Tension ties from the deck framing into the house framing that resist the deck pulling away from the wall, separate from the ledger gravity bolts
Lavatory: The bathroom hand sink, mounted drop-in, undermount, wall-hung, or vessel
Laydown / staging: Laydown is where material is received and stored; staging is where it sits ready to install, near the work
Layer coefficient: The relative structural strength per inch of a given layer material
Layered deterrence: Stacking measures so each covers the gap in the one before it, making the site the harder target rather than a fortress
Layout point / as-built: A designed point staked in the field, and the survey of what was actually built compared back to the model
Layout robot: A machine that prints or marks the building layout from the coordinated model directly onto the slab or deck, positioned against survey control
Layup: Protecting an idle boiler from corrosion, wet with treated water or dry with desiccant or nitrogen
LB / LL / LR: 90-degree elbow bodies named by the direction the cover or side opening faces: back, left, or right
lb N/1000 sq ft (lb N/M): Pounds of actual nitrogen per 1000 square feet, the standard turf application rate
lb-in / lb-ft / N-m: Pound-inches and pound-feet are the common torque units; 12 lb-in equal 1 lb-ft; newton-meters are the metric unit, with 1 lb-ft about 1.356 N-m
lb/sq ft (psf): Pounds per square foot, the unit for uniform distributed load; kilopascals in metric
lbf (pounds-force): The unit for concentrated, rolling, ultimate, and pedestal loads in US data sheets; newtons in metric
LC: Load constant, 51 lb (about 23 kg), the base weight before any conditions are applied
LCDI cord: Leakage-current detection and interruption power cord, the protection expected on plug-connected PTACs
LCR / LCRR / LCRI: EPA Lead and Copper Rule, its Revisions, and its Improvements; the federal rules for lead in drinking water
LDD: Luminaire dirt depreciation, light lost to dirt on the fixture between cleanings
Lead inductance: Voltage developed across the SPD leads during the fast surge, adding to the let-through; the reason for short leads
Lead RRP: EPA Renovation, Repair, and Painting rule requiring a certified firm and lead-safe practices when work disturbs pre-1978 paint in covered buildings.
Lead source: How a customer first found you; tracked on every record so you know which marketing pays
Lead-based paint: Paint with lead at or above the regulatory level, common before the 1978 residential ban; assume it in pre-1978 buildings unless tested otherwise
Lead-lag: A multi-pump control that runs a lead pump and stages lag pumps on as demand climbs, rotating which pump leads to spread wear [https://anvilfield.com/field-guides/glossary/lead-lag/]
Leader / conductor: The vertical drain pipe; a leader outside, a conductor inside the building
Leader cable: Non-sensing jumper cable that spans dry areas and connects sensing runs back to the panel
Leading vs lagging: Leading numbers predict (leads, backlog, close rate); lagging numbers record (revenue, net profit)
Leaf / ToR: The access switch connecting servers in a rack, usually the top-of-rack switch, uplinking to every spine
Leak detection: The sensors, alarms, and isolation that find coolant where it should not be and act on it before it reaches the IT
Leakage class: Smoke-damper rating (Class I or II) capping air leakage past the closed blades
Leakage class (CL): Allowable leakage in cfm per 100 sq ft at 1 in. w.g.; a lower number is a tighter duct [https://anvilfield.com/field-guides/glossary/leakage-class-cl/]
Leakage current: The small steady current through and across insulation that sets the megohm reading
Leakage factor (F): Allowable cfm per 100 sq ft at the test pressure, F = CL x P^0.65
Lean construction: Running the project as a production system aimed at reliable workflow by removing waste, the waiting and rework, rather than blaming the worker
LED power supply (class 2): A listed low-voltage supply, commonly class 2, converting 120 V to the 12 or 24 V DC the LED modules use
LEF: Load equivalency factor: how many standard axles' worth of damage one axle does, rising with about the fourth power of load
Legal outlet: A point the site is allowed to discharge to, a storm system, easement, watercourse, or its own ground, not the neighbor's lot
Legally required standby (NEC 701): Backup for code-required loads that are not immediate life safety, with a longer transfer expectation and its own coordination requirement
LEL / explosive atmosphere: Lower explosive limit; ventilation holds tank vapor below 10 percent of it
LEL / percent LEL: Lower explosive limit, the concentration at which a flammable gas can ignite, read on the meter as a percentage of it
LEL / UEL: Lower and upper explosive limits, the hydrogen range of about 4 to 75 percent by volume in air
Less-flammable fluid: High-fire-point dielectric liquid, fire point at or above 300 C (ester, silicone)
Level: NFPA 110 class for consequence of failure, Level 1 for life safety or Level 2
Level 1 / Level 2 / DCFC: 120 V AC; 208 to 240 V AC; and DC fast charging fed three-phase, delivering DC to the battery
Level 2: AC charging at roughly 208 V to 240 V, the common commercial and home charger range
Level 5: The top commissioning level, the integrated systems test, run after Levels 1 through 4 are signed off
Level of accuracy (LOA): The spec'd accuracy of the scan and model, per the USIBD specification; LOA says how correct, LOD says how complete
Leveling / scratch / wedge course: A thin, variable-thickness lift that fills ruts and lows before the wearing course
Leveling pad: The compacted crushed-stone base, commonly about 6 in, that the buried first course is set level on
Levels of finish 0 to 5: The GA-214 scale of how much taping and coating a wall gets; Level 4 is the standard painted finish, Level 5 adds a full skim coat for critical light and gloss
LFL / LEL: Lower flammable or explosive limit, the gas concentration below which the mixture will not ignite
LFP: Lithium iron phosphate (LiFePO4): lower energy density, more thermally stable, trending in data center backup
LFP / NMC: Lithium iron phosphate, higher onset and less violent; nickel manganese cobalt, higher energy and lower onset
LFP vs NMC: Lithium iron phosphate, more thermally stable and now dominant in stationary storage, versus nickel manganese cobalt, denser but with a lower thermal-runaway onset
LGR vs desiccant dehumidifier: Refrigerant unit that condenses moisture to low grains, versus a desiccant wheel for lower humidity and cold or bound-water drying
LI: Lifting index, load weight divided by RWL; above 1 signals increased risk
LID: Low impact development, the design approach that keeps runoff on site
Lidar laser scanner: An active instrument that fires laser pulses and times the return to measure precise distances and build a point cloud
Lien waiver: Signed release of mechanic's lien rights for an amount paid; conditional takes effect on payment, unconditional on signing [https://anvilfield.com/field-guides/glossary/lien-waiver/]
Life-cycle cost: Total cost over the life of an asset: first cost plus operating, maintenance, and replacement, often discounted to present value [https://anvilfield.com/field-guides/glossary/life-cycle-cost/]
Life-cycle cost (LCCA): The discounted total of building, maintaining, and rehabilitating a pavement over a common analysis period
Lift: The difference between condensing and evaporating temperature; the wider it is, the harder the compressor works [https://anvilfield.com/field-guides/glossary/lift/]
Lift (head): The pressure difference the compressor must develop between evaporator and condenser; high lift is the primary surge driver
Lift insert: Cast-in hardware the crane rigging hooks to, located and embedded per the engineered lift drawing
Lift station: A pump system that collects wastewater in a wet well and pumps it through a force main to a gravity sewer when it cannot get there by gravity
Lift vs stabilize: Raising the structure back toward level versus holding it where it sits so it stops moving
Lift-and-shift: A migration that moves the whole workload in one planned big-bang cutover window
Lights-out: An operating model where the site has no on-site staff and the unit is monitored and managed remotely
Likelihood of failure: The chance a tree or part fails within the assessment period, scaled improbable, possible, probable, or imminent
Lime vs Portland mortar: Soft, breathable, self-healing lime mortar for historic units versus hard, impermeable Portland-cement mortar
Limestone / marble chips: Calcium carbonate medium in a passive tank that neutralizes acid by contact
Line / load: On a protective device, line is the incoming supply, load is the protected downstream wiring
Line / trailer pump: Stationary pump that feeds concrete through hose and pipe laid out by hand
Line and load: LINE is the incoming supply terminals; LOAD feeds and protects downstream outlets
Line of credit: A revolving facility you draw on and repay, used to bridge timing gaps, not fund losses
Line sweep / PIM: Return loss, VSWR, and distance-to-fault on the line, and passive intermodulation, the interference from non-linear junctions
Line voltage: Building supply voltage, commonly 120 V, that holiday strings plug into; not the 12 V low-voltage landscape system [https://anvilfield.com/field-guides/glossary/line-voltage/]
Line vs load: On a GFCI, line is the incoming supply, load is the protected downstream wiring
Line-clearance arborist: A worker trained and qualified to perform tree work near energized conductors under OSHA 1910.269
Line-interactive / VI: Regulates voltage with an AVR, still transfers to battery on a true outage
Linear-drive optics (LPO): A pluggable optic with the DSP removed, driven directly by the switch silicon, for lower power while keeping the hot-swappable form factor
Linear-foot items: Materials bought by length off the edges and lines: drip edge, starter, cap, valley metal
Lined-clear opening: The inside duct dimension after the liner, the dimension that carries the air for sizing
Lineset: The insulated suction (vapor) line and the bare liquid line joining the units
Link budget / OSNR: The accounting of optical loss against the optic's power budget, and the optical signal-to-noise ratio the coherent receiver needs to recover the signal
Lion-tailing: Over-thinning that strips interior branches and leaves weight on the tips, weakening limbs and exposing bark
Liquefaction: Loose, saturated sand losing strength under earthquake shaking as pore pressure spikes and the grains float apart
Liquid-filled: Transformer with windings immersed in oil or a dielectric fluid
Liquidated damages: A fixed daily amount the contractor owes for late completion under the contract
Listed / UL assembly: A tested design, such as a UL design number, fixing the material, thickness, steel, and conditions that earn the rating
Listed vs recognized: A listed component is complete in itself; a recognized component goes into a larger assembly under stated conditions
Lithium-ion (LFP / NMC): Lithium iron phosphate, favored in data centers for thermal stability, versus the denser but less stable nickel manganese cobalt
Lithium-ion (LFP): Lithium iron phosphate, the lithium chemistry common in UPS service for its thermal stability, managed by a BMS
Live data feed: The real-time stream from the BAS and sensors, status, alarms, conditions, and energy
Live load: The movable design load from equipment, people, and service, in psf, that the structure is engineered to carry
Live-dead-live: Proving a voltage tester on a known live source, testing the circuit dead, then proving the tester again to confirm it did not fail [https://anvilfield.com/field-guides/glossary/live-dead-live/]
Living wall vs green facade: A living wall has plants rooted in a medium on the wall; a green facade has climbing plants rooted in the ground that grow up a trellis or cable.
LLD: Lamp lumen depreciation, the fade of LED output over life
LLF: Light loss factor, derates initial output to maintained, commonly 0.7 to 0.9
LOA / CFA: Letter of Authorization and Connecting Facility Assignment, the authorization plus the exact cabinet, panel, and port a cross-connect lands on; expires if not built in its window
Load (watts / amps): Power a display draws; sum the watts, divide by the supply voltage for amps to size against the circuit
Load and span class: NEMA VE-1 rating pairing a working load (lb per linear ft) with a support span (ft)
Load bank: Equipment that creates electrical or thermal load to stand in for the IT load during the test [https://anvilfield.com/field-guides/glossary/load-bank/]
Load chart: The platform decal giving allowable load by boom position and reach
Load class (EN 1433): Grate and channel strength rating, Class A pedestrian to Class F airport
Load constant: 51 lb (about 23 kg), the NIOSH base weight before conditions are applied
Load diversity: The degree to which loads do not peak together; high diversity is what makes oversubscription safe
Load management: Sharing capped power across dispensers so the service and the demand peak stay below the connected total
Load path: The chain carrying weight from the rack foot through the floor, beam, column, and foundation into the soil
Load securement: Restraining cargo and rack contents so they cannot shift or fly in a stop or a crash
Load share: Dividing real (kW) and reactive (kVAR) power between paralleled sets in proportion to rating
Load shed: Dropping the lowest-priority load when the set runs short, so the emergency load is the last affected [https://anvilfield.com/field-guides/glossary/load-shed/]
Load shedding: Briefly pausing or throttling non-urgent workloads during a grid event, then resuming
Load shifting: Moving deferrable compute to cheaper, cleaner, or less constrained hours; temporal flexibility
Load transfer: Moving the structure's weight from the old failing path onto the new piers or pit through a bracket or dry-pack [https://anvilfield.com/field-guides/glossary/load-transfer/]
Load vs non-load distress: Distress from traffic working a weak structure versus distress from age and climate working the surface
Load-bearing wall / shoring: A wall in the load path carrying weight from above; shoring is the temporary support that holds the load while it is removed and a permanent header goes in.
Load-demand dispatch: Running only the sets the load needs, starting and stopping sets on load with priority rotation for even run hours
Loadbreak elbow: A 200 A separable connector with an arc-interrupting tip that can be operated energized with a hot stick; a deadbreak elbow is 600 A and must be dead
Loaded crew rate: The crew's hourly cost including wage plus the labor burden of taxes, insurance, and benefits
Loaded rate: The hourly labor cost including wage, payroll burden, insurance, and small tools
Loam: A balanced blend of sand, silt, and clay that drains and holds water well, the target for topsoil
Local genotype / ecotype: A population of a species genetically adapted to local conditions, including its bloom and emergence timing
Local loop: The carrier circuit from their network into a building; interconnecting in the MMR avoids paying it across town
Localization: Tying the model's coordinates to the physical site control, also called site calibration
Locate ticket: The request you file; its number is your proof of notice and your key to checking responses
Location / asset tag: The grid coordinate, equipment tag, room, or lineup section that ties each photo, test, and signoff to the exact place the work is
Locator / wand: The handheld receiver that finds the sonde's position and depth from the surface
Lock-off / anchor set: The moment the wedges seat and hold; the small strand draw-in is the seating loss, about 1/4 in to 3/8 in
Locked-rotor / inrush current: The high current at the instant of starting, commonly six to eight times running current, which the branch device must pass
Lockout / restart / runback: Isolating energy before service; restart is automatic re-energizing, runback is a loaded incline rolling backward when the drive releases
LOD: Level of development: how detailed and reliable an element is, on a common scale of 100 concept, 200 generic, 300 accurate, 350 with connections, 400 fabrication, 500 as-built [https://anvilfield.com/field-guides/glossary/lod/]
Log-Tchebycheff: The traverse point spacing (from ISO 3966, used in ASHRAE 111) that makes the simple average of readings the true average velocity
Lone-worker system: Check-in, no-motion, panic button, and location built for the worker who works alone
Long-lead: Equipment whose order-to-delivery time is long enough that the order date, not the install date, controls the schedule.
Long-lead equipment: Gear with a long order time, the generators, switchgear, UPS, transformers, and chillers that gate the schedule
Long-lead item: Equipment with a lead time longer than the available schedule, such as switchgear, HVAC units, and custom glass [https://anvilfield.com/field-guides/glossary/long-lead-item/]
Longitudinal joint: The seam running with traffic between two adjacent paving passes or lanes [https://anvilfield.com/field-guides/glossary/longitudinal-joint/]
Longitudinal seam: The seam along the duct length, parallel to airflow, such as a Pittsburgh lock or snap-lock
Look-ahead: The three to six week window pulled from the CPM that the field builds from, with constraints cleared and crews assigned [https://anvilfield.com/field-guides/glossary/look-ahead/]
Look-ahead / make-ready: The roughly 6-week window where upcoming tasks are screened and their constraints removed so the work is ready
Loop / circuit: One continuous run of tube from the manifold supply, through the floor, and back to the manifold return
Loop resistance: The round-trip resistance of the conductors carrying current, the source of both the drop and the heat
Loose-fill vs unitary: Loose-fill is granular material at a set depth (engineered wood fiber, rubber mulch, sand); unitary is a bonded system (poured-in-place rubber, tiles)
Loose-laid: A membrane laid relaxed over the substrate with no field fasteners or adhesive, held only by ballast
Loose-shipped: Items shipped separately from the assembly, such as bus links, racking tools, keys, and spares
Loose-tube / ribbon cable: Fibers floating in buffer tubes, or bonded into ribbons for high count and mass fusion splicing
LoRaWAN / private LTE: LoRaWAN is a long-range, low-power network for small sensor packets; private LTE or 5G is a high-capacity network you control on site
Loss budget: The total optical loss a link can afford between transceivers, spent by fiber, connectors, and splices, in dB [https://anvilfield.com/field-guides/glossary/loss-budget/]
Loss factor: The share of theoretical coverage lost to surface texture, overspray, and waste; applied before ordering gallons
Loss inventory: The separate list of non-salvageable items, with photos, for the insurance claim
LOTO: Lockout/tagout, the isolation and verification of hazardous energy before work [https://anvilfield.com/field-guides/glossary/loto/]
LOTO (lockout/tagout): Isolating and locking a machine to a zero-energy state before anyone enters the danger zone
Louvered / motorized pergola: An aluminum pergola with adjustable blades that tilt for sun and close to a watertight roof, often on a motor with a sensor
Low delta-T: A return-to-supply temperature difference smaller than design, forcing excess flow and wasting plant capacity [https://anvilfield.com/field-guides/glossary/low-delta-t/]
Low-grade heat: Heat that is useful but at a low temperature, below what many uses want without upgrading
Low-head drainage: Water draining out the lowest emitters at shutoff on a slope, stopped with check valves
Low-intensity (tube): Gas heater with a steel tube emitter at a moderate surface temperature, commonly near 1100°F, over a long area
Low-lift vs high-lift grouting: Grouting the wall in short increments as it rises, versus laying it tall and grouting from the bottom in lifts with cleanouts
Low-slope: A roof too flat to shed reliably, commonly under roughly 2:12, waterproofed with a continuous membrane
Low-slope roof: A roof at a shallow pitch, commonly 1/4 in. per ft or less, where drainage and membrane integrity drive performance
Low-suction cutoff: A required control that shuts a booster down before it pulls a vacuum or negative pressure on the suction main
Low-voltage vector mapping (EFVM): A wetted-surface, perimeter-loop, two-probe method that maps the current vector to a breach; works under overburden
Low-water cutoff: The control that shuts the burner off when the boiler water line drops too far, preventing a dry-fire
Lower quarter: The driest 25 percent of the cups, which set the run time because they are the starved plants
LP vs natural gas: Propane (LP) is heavier than air and pools low, vented low; natural gas is lighter and rises, vented high; orifices and pressure differ [https://anvilfield.com/field-guides/glossary/lp-vs-natural-gas/]
LPD: Lighting power density, watts per square foot, capped by the energy code on a triggered alteration [https://anvilfield.com/field-guides/glossary/lpd/]
LSA: Local Service Ads, Google's pay-per-lead units with the verified badge
LSI: Langelier saturation index; negative is corrosive, positive is scaling
LSIG: Long-time, short-time, instantaneous, and ground-fault adjustable settings on an electronic trip unit [https://anvilfield.com/field-guides/glossary/lsig/]
LSL: Lead service line, the buried pipe from the main to the building when it is made of lead
LTTR: Long-term thermal resistance, the aged design R-value for polyiso per ASTM C1303
LTV (lifetime value): What a customer is worth across every job and referral, not just the first ticket
Lug: A connector that terminates a conductor to a stud, pad, or bar; mechanical or compression
Lumen: The unit of luminous flux, the total light a source emits
Lumen (lm): Total light output of a source, the quantity on a luminaire spec sheet
Lumen / efficacy: Light from the source; efficacy is lumens per watt drawn
Lumens: The amount of light a fixture puts out, sized to the feature and not to be overdone
Luminance: Brightness of a surface as the eye sees it, in candela per square meter, not the same as illuminance
Lux (lx): Illuminance of one lumen per square meter, the metric unit on most cut sheets [https://anvilfield.com/field-guides/glossary/lux-lx/]
LV / MV: Low voltage at 1000 V and below; medium voltage roughly 1 kV to 38 kV
LVT / LVP: Luxury vinyl tile and plank, the dominant commercial resilient product, glue-down or floating
LWA: Lightweight aggregate, the porous aggregate that cuts the density of the concrete
LWCO: Low-water cutoff, the control that shuts the burner when water level drops too low, preventing dry-firing of the vessel
LWIC: Lightweight insulating concrete, a poured deck over form deck that gives slope and holds water
M: Multiplier that reduces upstream fault current to the downstream point, 1 / (1 + f)
M / K rating: Crash-test ratings for vehicle barriers under ASTM F2656; M50 equals the older K12
M&IE: Meals and incidental expenses, the food-and-tips portion of per diem, often paid at a partial rate on travel days
M&O: Management and operations, the Uptime Institute assessment of the operations program
m2, m3: Drainage coefficients applied to the unbound base and subbase, adjusting for how well they drain
MAC: Move, add, or change to the plant; each one ends in an as-built record and label update or the administration drifts [https://anvilfield.com/field-guides/glossary/mac/]
Machine-room-less (MRL): A traction elevator with the compact machine inside the hoistway instead of a separate machine room
Macro fiber: Larger fiber at or above about 0.3 mm, synthetic or steel, that provides post-crack residual strength
Magnetic dirt separator: A separator with a magnet that captures magnetite from the flow, blown down or wiped clean on a schedule
Magnetite: Black iron-oxide sludge from corroding steel; abrasive to the pump and insulating on coils, and the thing a magnetic separator targets
MAHC: The CDC Model Aquatic Health Code, a model code many jurisdictions adopt or adapt for commercial pool depth, markings, slopes, drains, decks, and operation.
Main / exit cleanout: The cleanout serving the building drain to sewer junction, the access to the whole main
Main bonding jumper: The connection tying neutral to enclosure and ground, installed only at the service [https://anvilfield.com/field-guides/glossary/main-bonding-jumper/]
Main bonding jumper (MBJ): The single neutral-to-ground bond at the service, where a non-separately-derived generator's neutral stays bonded
Main drain entrapment: Suction holding a swimmer, hair, or clothing against a drain hard enough to trap or drown; the system's deadliest hazard
Main tee / cross tee / wall angle: The load-carrying main runner, the cross member that forms the tile module, and the L-shaped perimeter trim and support
Main vs circulation relief valve: The main relief is a large safety valve for over-pressure; the circulation relief bleeds a small flow to cool the pump at no-flow
Mainline vs lateral: Mainline stays under constant pressure to the valves; laterals carry one zone to its heads when it runs
Maintain temperature: The temperature the cable holds the pipe at, about 40°F for freeze protection
Maintenance agreement / RSA: The recurring service contract; recurring service-agreement revenue is abbreviated RSA
Maintenance bypass: Manual interlocked path to service the whole UPS with the load up
Maintenance of traffic (MOT): The phasing and work-zone plan that keeps the bridge open during the work, often by staged half-width construction
Make-ready: The service, conduit, and pads built ahead of and beyond the first chargers so expansion is a connection [https://anvilfield.com/field-guides/glossary/make-ready/]
Make-ready / constraint: Clearing what an activity needs, such as an RFI, submittal, material, or prior trade, before it is due
Make-ready / planning: Confirming a task has its materials, tools, equipment, information, approvals, and access in place before the crew starts it
Make-up water: Water added to the cooling tower to replace what is lost: evaporation plus drift plus blowdown [https://anvilfield.com/field-guides/glossary/make-up-water/]
Make-up water meter: The meter on the feed that records every gallon added, so a rising count flags a leak
Makeup: Fresh water added to replace evaporation, drift, and blowdown [https://anvilfield.com/field-guides/glossary/makeup/]
Makeup air: Air brought in to replace what is exhausted, by ducted outside air, transfer air, or surplus supply [https://anvilfield.com/field-guides/glossary/makeup-air/]
Makeup air balance: Replacing the air the hood exhausts so the building does not go negative, with the kitchen held slightly negative to the dining room
Maltenes: The lighter, oily fractions of asphalt binder that keep it soft and ductile, lost to oxidation as the pavement ages
Management reserve: Money held above the estimate baseline for unknown-unknowns, the unforeseeable, usually controlled by the owner or senior management rather than the estimator.
Mandrel: A rigid slug pulled through each duct to prove it is clean, round, and clear before cable
Manifest: The hauler's disposal receipt proving the grease reached a legal disposal site
Manifold: The supply and return assembly where all loops in a zone connect, carrying flow meters and actuators
Manifold / probes: The gauge set or wireless clamp-on probes that read suction and liquid pressure and temperature
Manifold gauge set: The gauges, hoses, and valves that read refrigerant high and low pressure and connect the system to pump, recovery, and cylinder
Manifold pressure: The gas pressure the valve delivers to the burners, set to the data plate
Manometer: Reads pressure in inches of water column: duct static, gas manifold pressure, and draft
Manpower: Labor headcount on the job, recorded by company, trade, and area, ideally tied to a cost code
Manpower by area: The head count of workers in each zone, broken out by trade, rather than a single site total
Mantrap / portal / vestibule: Interlocked doors passing one cleared person at a time to defeat tailgating
Manual D: ACCA's residential and light-commercial duct design procedure, built on available static pressure and the friction rate
Manufacturer warranty: The product maker's coverage of the equipment or material itself, usually longer than the workmanship warranty
Map pack / local pack: The three-business block of local results above the regular search listings, where review volume, recency, and rating heavily influence who appears
Margin: The share of the final price left after cost, as a percentage of price. Always a smaller percent than the markup for the same job. [https://anvilfield.com/field-guides/glossary/margin/]
Margin fade: The estimated job margin eroding toward the actual as costs run over; the WIP shows it early
Marine-grade fastener: Hardware rated for immersion, 316 stainless in salt water or hot-dip galvanized for fresh, matched to avoid galvanic attack
Marked volume: The cubic-inch capacity stamped on a body, required before any splice, tap, or device is allowed in it
Marked-up set: Any field set in progress, the live working red-line before it becomes the formal as-built
Market-based vs location-based: Carbon valued at contracted power versus the average emissions of the physical grid; report both
Markup: The amount added on top of cost, as a percentage of cost. A 25 percent markup adds a quarter of the cost to the price. [https://anvilfield.com/field-guides/glossary/markup/]
Markup vs margin: Markup is the multiplier on cost; margin is profit as a percent of price; they are different numbers [https://anvilfield.com/field-guides/glossary/markup-vs-margin/]
Masonry / CMU: Units laid in mortar; CMU is the concrete masonry unit, the concrete block
Mass concrete: Any placement large enough that hydration heat must be managed to control cracking, often a least dimension of about 3 to 4 ft
Mass notification / ECS: Emergency communication system: intelligible emergency voice and visible messaging to occupants, life-safety equipment under NFPA 72
Mass-concrete (pit) underpinning: Hand-dug pits in sequence under a footing, filled with concrete to a deeper bearing level
Massing: Planting one variety in solid blocks or drifts so the color reads from a distance, rather than dotting single plants
Mast-climbing work platform (MCWP): A powered deck that climbs a mast bolted to the building on a rack-and-pinion drive; the whole installation, the platform, mast, ties, and base
Master mixing valve: Source valve at the heater (ASSE 1017) that tempers storage down for the distribution system
Master valve: A source valve the controller opens only while a zone runs, limiting how long a break can flow
Mat / raft: One large slab carrying the whole building, for heavy loads or weak soil
Matched precipitation: Every head on a zone applying the same depth per hour, the condition for a fixable schedule
Matched precipitation rate: All heads on a zone applying the same depth per hour, so one run time waters evenly
Matched set: Belts within a tight length tolerance, replaced together on a multi-belt drive
Material-only warranty: Coverage for the material alone, no labor, usually prorated; the weakest warranty type
Materialman's lien: A supplier's claim against the property where unpaid material was furnished, governed by state law
Matrix and aggregate: The matrix is the binder and background color; the aggregate is the decorative chip, marble, glass, granite, or recycled glass
Mature size: The height and spread a plant reaches at maturity, the number that should drive selection and spacing
Maturity (ASTM C1074): An in-place strength estimate from the concrete's temperature-and-time history against a calibrated curve
Maturity index: The single number combining time and temperature, either TTF or equivalent age
Maturity method: Estimating in-place strength from the time-temperature history at a sensor [https://anvilfield.com/field-guides/glossary/maturity-method/]
MAU (makeup air unit): The supply fan and heating section that replaces the air a kitchen hood exhausts
MAWP: Maximum allowable working pressure, the pressure the relief valve set point must not exceed
Max-to-min ratio: Uniformity limit, capped at 40 to 1 so no single dark spot on the path
Maximum dry density (MDD): The peak dry unit weight a soil reaches in the Proctor test, the 100 percent reference
Maximum intended load: The total of workers, tools, material, and any force on the scaffold; capacity is at least 4 times this
Maximum series run: The manufacturer's limit on strings connected end to end before the run is overloaded and the fuse blows
Maximum system voltage: The highest voltage the array can reach at the coldest expected temperature, capped by the equipment rating
MBB / BBM: Make-before-break for the maintenance bypass; break-before-make for the STS source swap
MBCx: Monitoring-based commissioning, using continuous data and analytics to keep a building commissioned over time
MBH: Thousands of Btu per hour, the common hot water and small boiler output unit [https://anvilfield.com/field-guides/glossary/mbh/]
MBH / MMBtu/hr: Thousands and millions of BTU per hour, the units boiler input and output are rated in
MBJ / SBJ: Main bonding jumper at the service and system bonding jumper at a separately derived system, the single neutral-to-ground bond [https://anvilfield.com/field-guides/glossary/mbj-sbj/]
MC / AC cable: Metal-clad cable and armored cable, conductors with armor in one assembly
MC4 connector: The standard PV DC connector, and the most common single failure and fire point when crimped poorly or mated across brands
MCA / MOCP: Minimum circuit ampacity sizes the conductors; maximum overcurrent protection caps the breaker or fuse [https://anvilfield.com/field-guides/glossary/mca-mocp/]
MCCB: Molded-case circuit breaker, the general-purpose thermal-magnetic standard
MCOV: Maximum continuous operating voltage the device tolerates without degrading; set above the system voltage [https://anvilfield.com/field-guides/glossary/mcov/]
MCP: Motor circuit protector, an instantaneous-trip-only breaker used in a listed combination starter
MDA / HDA / EDA: Main, horizontal, and equipment distribution areas, the TIA-942 spaces from the central cross-connect out to the rack
MDF / IDF: Main and intermediate distribution frames, the main and floor-level telecom rooms
MDR: Motorized driven roller, a roller with a low-voltage motor inside that drives a zone, the basis of zoned accumulation
Mean radiant temperature (MRT): Average temperature of the surrounding surfaces, which drives comfort along with air temperature
Means of egress: The full path out: exit access, exit, and exit discharge to the public way
Measured mile: A loss-of-productivity method comparing the rate in an unimpacted period against an impacted period of similar work, the gap being the loss
Measurement and verification (M&V): Proving actual savings by comparing normalized energy before and after a measure, per the IPMVP options A to D.
MEC / MDC: Minimum extinguishing concentration, the percentage that just puts the fire out, and minimum design concentration after the safety factor
Mechanical seal: Two lapped faces, one rotating and one fixed, sealing the shaft with a thin water film; it must not run dry
Mechanical splice: A coupler that joins two bars and carries the force through the device, graded by strength developed [https://anvilfield.com/field-guides/glossary/mechanical-splice/]
Mechanical splice / coupler: A device that joins two reinforcing bars end to end and transfers force bar to bar, not through concrete bond
Mechanical vs ventilation dehumidification: Mechanical uses a refrigeration coil to condense moisture out; ventilation brings in drier outdoor air and exhausts the moist air
Mechanically attached: Racking bolted to the structure through flashed penetrations; lighter load, more holes
Mechanics lien: A security claim recorded against improved real property when a contractor, sub, supplier, or laborer is not paid; it can cloud title and, in most states, be foreclosed. [https://anvilfield.com/field-guides/glossary/mechanics-lien/]
Medical surveillance: Baseline and periodic exams, including chest X-ray and spirometry, offered to workers who must wear a respirator 30 or more days a year
Medium temp / low temp: Medium temp is a cooler holding product above freezing, commonly in the mid-30s°F; low temp is a freezer holding product frozen, commonly near 0°F to about -10°F
Medium voltage: Distribution voltages roughly 5 to 35 kV, between low voltage and high voltage; sometimes given as 2.4 to 35 kV
Meet-me room (MMR) / cross-connect: The MMR is where carriers and tenants interconnect; a cross-connect is the physical cable linking two endpoints through it
Megger / insulation resistance: A DC test of the cable jacket's resistance in megohms, taken before and after install
Megohm: Unit of insulation resistance, one million ohms; 1 gigohm equals 1000 megohms
Megohmmeter (megger): An insulation-resistance tester applying a high DC voltage, read in megohms, de-energized only [https://anvilfield.com/field-guides/glossary/megohmmeter-megger/]
Mellowing: The rest period after first mixing that lets lime react through plastic clay before final compaction
Membrane penetration: A breach in only one face of a rated assembly
MEMS: Micro-electro-mechanical systems; here, an array of tiny tilting mirrors that steer the optical beam inside an OCS
MEP: Mechanical, electrical, and plumbing, the systems that carry most of a data center's cost and schedule
MEP make-safe / LOTO: Capping, disconnecting, locking out, and verifying dead the mechanical, electrical, and plumbing before cutting; LOTO is lockout-tagout of hazardous energy.
MERV: Minimum Efficiency Reporting Value, the filter's particle-capture rating; higher is finer and more restrictive [https://anvilfield.com/field-guides/glossary/merv/]
MERV-A: The MERV after Appendix J conditioning discharges electrostatic media, the in-service efficiency
Mesh: Filter fineness, openings per linear inch; 150 to 200 mesh is the common drip range
Mesh-BN: Mesh bonding network in the equipment room, commonly 1/0 to the busbar and 6 AWG to each rack
Metadata / EXIF: The data stored with an image, including timestamp, GPS location, and device, plus any tags or description added at capture
Metal roof restoration: Renewing an aging metal roof in place by treating rust, repairing fasteners and seams, and coating it, instead of a tear-off
Metal-bond vs resin-bond diamond: Metal bonds cut and expose the slab, resin bonds polish it to gloss, with a transitional step between
Metal-clad: Medium-voltage switchgear with each compartment isolated by grounded metal barriers, per IEEE C37.20.2
Metal-clad switchgear: MV switchgear with drawout breakers and fully barriered compartments for the breaker, bus, and terminations
Meter setter / horn: The rigid bracket or yoke that holds the meter to its lay length and carries the valves, so a meter can be changed without cutting pipe
Metered / outlet-metered: A strip that reads total current at the inlet, or current per outlet
Metered vs committed billing: Metered bills the kWh you actually use; committed bills a flat charge for the reserved breaker capacity
Metering device: The restriction between the high-pressure liquid line and the low-pressure evaporator that drops pressure and meters liquid into the coil
Method A / B / C: The three TIA-568 channel schemes: straight trunk with a flipped cord, reversed trunk, or pair-flipped trunk
MEWP: Mobile elevating work platform, the ANSI A92 term covering boom, scissor, and vertical mast machines
mg/L: Milligrams per liter, equal to parts per million in water; the unit for dose and residual
MHz: Megahertz; the frequency the link is swept across, 500 MHz for Cat6A
MIC: Microbiologically influenced corrosion, localized pitting driven by bacteria in residual water, a common dry-system failure
Micro data center: A small, self-contained unit, from a single rack to a few cabinets, with integrated cooling, power, monitoring, and security
Micro fiber: Fine fiber under about 0.3 mm that controls plastic-shrinkage cracking and gets no structural credit
Micro milling: Fine milling with tight tooth spacing for a smooth, finely textured surface
Micro-surfacing: A cold mix using a polymer-modified emulsion that sets chemically, reopens to traffic in about an hour, can be placed thicker, and can fill ruts
Microbubble air separator: A coalescing device, best placed at the hot, low-pressure heat-source outlet, that merges tiny bubbles so they rise and vent
Microbubble separator: An air separator with a coalescing medium that merges tiny microbubbles into bubbles large enough to rise and vent
Microburst: A traffic spike that saturates a link or overflows a buffer for well under a second, invisible to slow polling but enough to drop packets
Microclimate: A small pocket where sun, wind, moisture, or temperature differs from the rest of the site, shifting the effective zone
Microgrid: A local power system of sources, storage, and load that can island or run grid-parallel under one controller
Micron: A unit of vacuum, microns of mercury absolute, used during evacuation; about 500 microns is a common target before charging [https://anvilfield.com/field-guides/glossary/micron/]
Micron gauge: Electronic vacuum gauge with a thermistor sensor that reads deep vacuum in microns; the manifold gauge cannot [https://anvilfield.com/field-guides/glossary/micron-gauge/]
Microns: Unit of vacuum during evacuation; about 500 microns is a common target before charging, confirmed by a decay test
Micropile: A small-diameter drilled-and-grouted steel pile for high loads, limited access, or rock
Microtopping: A very thin polymer-rich skim, around 1/16 to 1/8 in, troweled for a decorative finish
Mil: One thousandth of an inch (0.001 in), about 25.4 microns; the unit for coating film thickness [https://anvilfield.com/field-guides/glossary/mil/]
Mil / DFT: A mil is 0.001 inch; dry film thickness is the cured coating thickness measured in mils
Mill and overlay: Resurfacing by milling off the worn top layer with a cold-milling machine, then paving a new lift over it
Mill-and-fill: Milling off the surface course and replacing it with an overlay of similar thickness
Miller Act: Federal law requiring performance and payment bonds on federal construction over a dollar threshold; states have Little Miller Acts
Min / max airflow: The throttled floor and the design ceiling the box modulates between; min carries the ventilation requirement
Mineral filler: Portland cement or hydrated lime added to the mix to add cohesion and react with water to drive the break
Minimum airflow: The throttled-down floor, set to meet ventilation without overcooling, bounded by 62.1 and 90.1
Minimum approach distance (MAD): The required clearance from an energized line, set by voltage; assume the line is live [https://anvilfield.com/field-guides/glossary/minimum-approach-distance-mad/]
Minimum bend radius: Tightest allowed bend as a multiple of cable diameter, measured to the inside of the bend
Minimum flow: The lowest flow the manufacturer allows through the heat exchanger; below it the water near the fire overheats [https://anvilfield.com/field-guides/glossary/minimum-flow/]
Minimum outside air: The ventilation floor from ASHRAE 62.1, a people component plus an area component, that DCV cannot go below
Minimum position: The damper opening held for ventilation when free cooling is locked out
Minimum primary airflow: The lowest airflow a box will deliver, set for ventilation per ASHRAE 62.1 and the reheat floor
Minutes: The official record of a meeting: decisions, attendees, action items, and open items, issued and allowed to stand corrected
Miscibility: How well the oil mixes with the refrigerant; poor miscibility means the oil drops out and stays
Mitigation: The response that reduces risk: prune, reduce weight, cable or brace, move the target, monitor, or remove [https://anvilfield.com/field-guides/glossary/mitigation/]
Mitigation / restoration: Mitigation is the emergency work that stops the loss from worsening; restoration is the rebuild of what was removed
Mitigation duty: The policy obligation, from ISO-form sue-and-labor language, to take reasonable steps to protect property from further loss after a covered event
Mix design: The approved proportions of cement, water, aggregate, and admixtures to meet specified strength, durability, and workability
Mixed bed: Cation and anion resin blended in one vessel for the highest-purity polish
Mixing / injection: Blending hot source water with cooler loop return to hold the low radiant supply temperature
Mixture: Two or more different grass species planted together
MLO: Main lugs only; a panel with no main breaker, protected by an overcurrent device upstream
MLPE: Module-level power electronics, microinverters or DC optimizers that control voltage at each module [https://anvilfield.com/field-guides/glossary/mlpe/]
MLV (minimum local value): The lowest F-number allowed in any single test section, so an average cannot hide a local failure
MMR: Meet-me room, the neutral space where carriers and tenants interconnect through cross-connects, often split into MMR-A and MMR-B for redundancy
MMR / meet-me room: The space where carriers and networks interconnect inside the building
Mob / demob: Mobilization and demobilization, the trip to start the job and the trip home, and the travel pay that covers them
Mobilization: Bringing the crew, equipment, and temporary facilities onto the site to start work; demobilization is removing them at the end [https://anvilfield.com/field-guides/glossary/mobilization/]
Mock-up and field water test: A full-size test wall proven for air, water, and structural load before the building, then confirmed on the installed wall by an ASTM E1105 water test.
Mod-bit: Modified bitumen, an asphalt sheet membrane reinforced with mat and modified with SBS or APP polymer
Modal dispersion: Pulse spreading from many modes arriving at different times, the limit on multimode distance
Modbus: A register-based protocol common on chillers, meters, and UPS; no built-in object model, so scaling and register maps must be verified
Modbus / BACnet / IEC 61850: The common protocols meters and relays use to report to the EPMS server
Mode of action / RAC group: How a product kills, grouped by IRAC, FRAC, or HRAC number on the label, the basis for rotation
Mode-field diameter (MFD): Width of the light-carrying region in singlemode; a mismatch causes built-in splice loss
Model + control dependency: The rule that a robot is only as accurate and correct as the coordinated model and the survey control it builds from; a bad model or control yields bad output
Model-to-field: Exporting coordinated points from the BIM model to the instrument so the field builds exactly to the model on the project coordinate system
Modified bitumen: Polymer-modified asphalt low-slope sheet, applied by torch, mop, cold adhesive, or self-adhered
Modified Proctor (ASTM D1557): The higher-energy test, roughly 4.5 times the effort, higher MDD and lower OMC
Modular / panel vs felt / pocket: Modular uses pre-grown cassettes or trays of media on a frame; felt uses geotextile pockets fed hydroponically with no soil
Modular / self-contained / remote: Head on a separate bin or dispenser; maker and bin in one undercounter cabinet; head inside with the condenser mounted outside
Module: The repeating stall-plus-aisle-plus-stall unit, about 60 ft for double-loaded 90-degree parking
Modulus of rupture (MR): Flexural strength of the concrete, the property that governs slab thickness
Mogul: An oversized conduit body with extra internal depth for the bending radius of large conductors
Moisture gradient: The difference in moisture content between the drier top and the wetter bottom that drives the curl
Moisture mitigation: A topical barrier, usually an epoxy coating, applied when the slab tests over the limit
Moisture survey: An infrared, nuclear, or capacitance scan, verified by core cuts, that maps wet insulation before a roof is coated [https://anvilfield.com/field-guides/glossary/moisture-survey/]
Moisture test (MVER / RH): Slab moisture measured by ASTM F1869 emission rate or ASTM F2170 in-situ relative humidity before a bonded pour
Mold remediation: Controlled removal of mold growth plus correction of the moisture source that fed it
Monitored vs recorded: Monitored is watched and responded to live; recorded is stored for review after the fact
Monitoring / scouting: Walking a property on a schedule to read plants for early stress and feed the pest and disease decisions
Monitoring-based commissioning (MBCx): Continuous commissioning run by analytics so the tuning never stops
Monopole / lattice / guyed: The three tower families: a single steel tube, a bolted self-support truss, and a slender mast held by guy cables
Monostand: A single cultivar of a single species across a whole lawn, the fragile option
Monostrand: A single seven-wire strand, greased and sheathed, the common unbonded building tendon
MOP: Method of Procedure; the approved step-by-step script, with risk and rollback, for changing a critical component's state [https://anvilfield.com/field-guides/glossary/mop/]
Mortar matching: Matching the new mortar to the original in type, lime content, color, sand, and profile, proven by a test panel
Mortar types M, S, N, O: ASTM C270 types by decreasing strength; match to the unit, not always the strongest
MOT / traffic control plan: Maintenance of traffic, the plan for moving vehicles and pedestrians safely past the work in the public right-of-way
Mounting height: Height of the discharge nozzle above the floor, the distance the throw has to cover
Mounting hole pattern: The repeating three-holes-per-U spacing that lets any compliant device land on the same holes
MOV: Metal-oxide varistor, the sacrificial element in most SPDs that degrades with each surge
Movement / expansion joint: A joint built to open, close, and shear, sealed with a centerbulb waterstop
Movement class: The plus-or-minus percentage of joint width a sealant can take, per ASTM C920, such as class 25
Movement joint (EJ171): A soft, sealant-filled joint at the perimeter, in the field, over slab joints, and at changes of plane that lets the tile and building move without tenting.
Movement range: The total movement the joint must absorb, from thermal swing, moisture, settlement, creep, and seismic drift combined
Movement rating: How far a cover can let the joint open, close, and on a seismic joint shear, before the bellows is overworked
MPII: Manufacturer's printed installation instructions, the install procedure ACI 318 Chapter 17 references [https://anvilfield.com/field-guides/glossary/mpii/]
MPO / MTP: Multi-fiber push-on connector carrying 8 to 24 fibers in one ferrule; MTP is a brand of MPO, the basis of parallel optics [https://anvilfield.com/field-guides/glossary/mpo-mtp/]
MR (modulus of rupture): Flexural strength of concrete, the tensile stress in bending at which it cracks, in psi
MS4: Municipal separate storm sewer system, the permitted public storm network
MSD: Musculoskeletal disorder, injury to muscles, nerves, tendons, joints, or discs, often from overexertion or repetition
MSE wall: Mechanically stabilized earth: a reinforced soil mass behind a wall face, used for tall walls
MTR (material test report): The mill certificate proving the pipe or component is the alloy and grade the spec required
MTTD / MTTR: Mean time to detect a fault; mean time to restore, repair, or resolve, which are different measures, so state which one you mean
MTV (material transfer vehicle): Machine between truck and paver that re-blends gradation and temperature before the paver
mu: Coefficient of friction between the cable jacket and the conduit, roughly 0.5 dry and 0.2 lubricated
Mud sill: A plank or pad under the base plate that spreads the leg load across soft or uneven ground
Mulch volcano: Mulch piled in a cone against the trunk; rots the bark and invites girdling roots
Multi-tap: A transformer with several voltage output terminals (12, 13, 14, 15 V) used to offset voltage drop on long runs
Multi-tap transformer: A transformer with 12, 13, 14, 15 V output terminals used to offset voltage drop on long runs
Multimeter: Reads voltage, resistance, continuity, and capacitance; the core electrical diagnosis instrument
Multimode (MM): Fiber with a ~50 micron core carrying many modes, shorter reach from modal dispersion, VCSEL source, graded OM1 to OM5
Multiplier: The factor by angle that turns offset depth into the distance between the two bends
MUTCD: Manual on Uniform Traffic Control Devices, the FHWA reference for marking colors, widths, and retroreflectivity [https://anvilfield.com/field-guides/glossary/mutcd/]
Mutual heating: The temperature rise each loaded conductor causes in its neighbors, which lowers the ampacity of every conductor in the bank
MV / HV: Medium voltage, roughly 1 to 35 kV, and high voltage, the transmission levels above it
MV / LV: Medium voltage, roughly 1 kV to 35 kV, and low voltage, 1000 V and below
MVER: Moisture vapor emission rate, pounds per 1000 square feet per 24 hours, from the ASTM F1869 calcium chloride test [https://anvilfield.com/field-guides/glossary/mver/]
MVER (ASTM F1869): Moisture vapor emission rate, pounds per 1000 sq ft per 24 hr by calcium chloride [https://anvilfield.com/field-guides/glossary/mver-astm-f1869/]
MVER / RH: Moisture vapor emission rate (ASTM F1869, lb/1000 sf/24 hr) and internal relative humidity (ASTM F2170, percent), the moisture tests before a coating
MVR: Motor-vehicle record, the state DMV driving history showing license status, violations, convictions, suspensions, and crashes
MW / GW: Megawatt and gigawatt, the scale of a data center campus load
MW capacity: Megawatts of electrical load a site can be delivered and the building can use, the headline number of a campus
MWBC: Multi-wire branch circuit: two opposite-phase hots sharing one neutral, with a simultaneous disconnect [https://anvilfield.com/field-guides/glossary/mwbc/]
Myers hub / raintight hub: A listed sealing conduit fitting that holds the watertight rating at an entry
n: Number of conductors per phase in parallel for the run
N / N+1 / 2N: Redundancy levels, from no spare, to one extra component, to two full independent systems [https://anvilfield.com/field-guides/glossary/n-n-1-2n/]
N / R / P filter: Particulate filter oil resistance: N not oil-resistant, R oil-resistant, P oil-proof
N per 1000 sq ft: Pounds of actual nitrogen per thousand square feet, the turf fertilizer unit
N+1: One more cooling unit than the row needs, so any single unit can drop and the survivors still hold the inlets [https://anvilfield.com/field-guides/glossary/n-1/]
N+1 / 2N: One spare unit beyond the need, or two full systems each carrying the whole load, the common redundancy arrangements [https://anvilfield.com/field-guides/glossary/n-1-2n/]
N+1 redundancy: One fan more than the design airflow needs, so any single failure still meets design
N, N+1, 2N: Redundancy notations: just enough, one spare, and two full independent systems
N-P-K: Percent by weight of nitrogen, available phosphate, and soluble potash on the bag, in that order
N<sub>awg</sub>: Number of counted conductors of a given wire size
n_c, L_c: Count of mated connector pairs and the per-pair loss allowance in dB
N_drops: Number of drops in the zone, from the panel schedule and rack elevations
n_s, L_s: Count of splices and the per-splice loss allowance in dB
NAC: Notification appliance circuit, the power circuit feeding horns and strobes
NADCA Vacuum Test: Gravimetric post-cleaning test measuring debris left on the cleaned surface against the standard limit
Nail line / nail zone: The marked band where nails go, so each fastener holds two courses; nails above or below it fail
Nail sickness: Widespread loss of slates when corroded original fasteners fail, even though the slate itself is sound
Nailable deck: A deck that accepts fasteners; some only with special auger or base-sheet fasteners
Nailer: Continuous perimeter wood blocking the edge metal and cleat fasten into, part of the wind load path
Nameplate kVA: The unit's isolation rating, much smaller than the load it supports in the buck-boost connection
Nameplate rating: The manufacturer's worst-case maximum draw, well above the actual measured load
Nameplate vs actual: Nameplate is the worst-case maximum draw; actual is the measured load, commonly a fraction of nameplate [https://anvilfield.com/field-guides/glossary/nameplate-vs-actual/]
Natatorium: An indoor swimming pool and the room enclosing it, treated as a contained, controlled environment
NATE: North American Technician Excellence, the recognized voluntary HVAC competency credential [https://anvilfield.com/field-guides/glossary/nate/]
Nativar: A cultivar of a native species; wildlife value varies and some offer less pollen and nectar than the straight species
Native plant: A species that occurred in an area before widespread human introduction, judged at the ecoregion scale, not the country
Native vs adapted: Native plants grew in the region naturally; adapted plants are non-natives that thrive locally without becoming invasive [https://anvilfield.com/field-guides/glossary/native-vs-adapted/]
Natural frequency: The rate the equipment-on-mount system bounces at; kept well below the operating speed
Natural slate: Roofing shingles split from quarried metamorphic stone, as opposed to molded synthetic or composite slate
NC: Noise criterion, a single-number rating of a device's sound level used to hold it under a room limit
NDE / radiography: Nondestructive examination of welds (VT, PT, RT, UT); radiography is the x-ray or gamma volumetric method
Ndesign: The design gyration count, set by traffic, where the mix is held to 4 percent air voids
NDIR: Nondispersive infrared, the method good CO2 sensors use to measure carbon dioxide directly by infrared absorption
NDL warranty: No-dollar-limit warranty: manufacturer coverage for material and labor with no cap on repair cost, issued after inspection [https://anvilfield.com/field-guides/glossary/ndl-warranty/]
Near-miss: An event that could have caused injury but did not; a free lesson that feeds back into the JHA and the talk [https://anvilfield.com/field-guides/glossary/near-miss/]
NEBB / AABC: The bodies that publish TAB procedural standards, report forms, and the firm and technician certifications
NEC 110.14(D): The code section requiring terminations to be tightened to the manufacturer's value, with a calibrated torque tool or approved means where a value is given
NEC 242: The NFPA 70 article governing overvoltage protection and SPDs, formerly Article 285
NEC 645: NFPA 70 Article 645, the optional rules for information technology equipment rooms; 645.10 is the disconnecting-means (EPO) section
NEC 700 / 701 / 702: Emergency, legally required standby, and optional standby articles that set the transfer-time class and the wiring rules [https://anvilfield.com/field-guides/glossary/nec-700-701-702/]
NEC 706 / 705: The NEC articles for energy storage systems (706) and for interconnection to the utility supply (705)
NEC Article 555: The National Electrical Code article governing marina and dock electrical, written to keep leakage current out of the water
NEC Article 625: The NEC article governing EV supply equipment, including the continuous-load and disconnect rules
Neck vs face velocity: Air speed in the inlet collar (neck, the noise source) versus across the visible face after spreading
Negative air / dust containment: Sealing the work area with poly and zip walls and holding it below surrounding pressure with HEPA negative-air machines so dust stays in the work zone.
Negative float: A signal the work is behind: the calculated finish lands past a deadline by that many days
Negative pressure: Lower air pressure inside the containment than around it, so any leak pulls inward, not out
Negative pressure room: A room held below its surroundings so air flows in, protecting everyone else from the patient (AII)
Negative side: The interior, dry face; used when the exterior cannot be reached
Negative space pressurization: Keeping the pool room at lower pressure than adjacent spaces so its humid, corrosive air stays in rather than spreading
Negative-air machine: HEPA-filtered vacuum unit that holds the system under continuous negative pressure during cleaning
Negative-pressure enclosure: A sealed poly containment held below surrounding pressure by HEPA negative-air machines so leakage flows inward
Neher-McGrath: The 1957 calculation method behind engineered duct-bank ampacity and the NEC Annex B and 310.60 figures
NEMA 250: The standard that defines enclosure types and what each protects against
NEMA 3R: A raintight enclosure rating for outdoor use, keeping rain and sleet out with a path to drain condensation
NEMA enclosure type: The rating for where an enclosure may go: 1 indoor, 3R outdoor, 4/4X wet or corrosive, 7 hazardous, 12 dusty
NEMA load class: A tray's working load per foot on a given span: class A 50 lb/ft, B 75 lb/ft, C 100 lb/ft, per NEMA VE 1
Neocloud / GPUaaS: A specialist operator renting GPU capacity as a service for AI and HPC workloads
NESHAP: EPA National Emission Standards for Hazardous Air Pollutants, the federal rule that governs asbestos in renovation and demolition, including the survey, abatement, and notification.
NESHAP / AHERA: EPA NESHAP (40 CFR 61 Subpart M) governs emissions, notification, and waste; AHERA governs asbestos in schools
Net 30 / net 60: Full amount due in 30 or 60 days, an interest-free loan from the supplier for that term
Net depth: The depth the plants need for the period after subtracting effective rainfall
Net free area: The actual open area through a grille or louver, smaller than the nominal opening size [https://anvilfield.com/field-guides/glossary/net-free-area/]
Net free area (NFA): The actual open airflow area of a vent after screen and louver, rated in square inches [https://anvilfield.com/field-guides/glossary/net-free-area-nfa/]
Net need: The depth in inches the plants require for the period after subtracting effective rainfall
Net pressure: Discharge pressure minus suction pressure, the pressure the pump itself added and the value plotted on the curve
Net profit: What is left after overhead comes off gross margin; the company's true profit
Net terms / due on receipt: When payment is due; Net 30 means 30 days from invoice, due on receipt means when sent
NETA ATS: Acceptance Testing Specifications, the standard for field acceptance tests on electrical power equipment
NETA MTS: ANSI/NETA Maintenance Testing Specifications, the reference for in-service test methods and values
NETD: Noise-equivalent temperature difference, the camera's thermal sensitivity, which sets the smallest rise it can resolve
Neutral (grounded): The return conductor; lands on the silver screw, never on the green
Neutral bonding: The neutral-to-ground connection, made in exactly one place; a second bond puts neutral current on the grounding conductor
Neutral load: The maximum unbalanced load the neutral carries, sized under 220.61
Neutral pressure plane: The height in a building where inside and outside pressure are equal
Neutralization: Bringing the waste pH into the dischargeable range before it joins the sanitary sewer
Neutralizer: Media that raises the pH of acidic condensing-appliance condensate before disposal
Neutralizing: Stopping the acid reaction and lifting residue with a baking soda or ammonia solution, then rinsing clean before sealing
Neutralizing amine: A chemical that travels with the steam and neutralizes carbonic acid in the condensate return
Neutralizing media: Calcium carbonate (limestone, marble, calcite) or magnesium oxide that reacts with the acid and raises pH
NEVI uptime: The federal corridor requirement that each port average over 97 percent uptime on a rolling 12-month basis
NEXT / PSNEXT: Near-end crosstalk between pairs, and the power-sum from all pairs at the near end
Next upstream manhole: The public-sewer manhole whose cover elevation sets the code trigger for protecting lower fixtures
NFPA 110 Class: The runtime classification, the minimum hours the plant runs at rated load without refueling, such as Class 72
NFPA 13: The standard for the installation of sprinkler systems; 13R covers low-rise residential, 13D covers one- and two-family dwellings
NFPA 20 / 14: The standards for the fire pump and the standpipe and hose system, respectively
NFPA 20 / NFPA 25: NFPA 20 governs the installation and the acceptance test; NFPA 25 governs the recurring inspection, testing, and maintenance
NFPA 58: The LP-Gas Code, governing the container, placement, regulators, and storage
NFPA 70E: The NFPA standard for electrical safety in the workplace; the program, boundaries, PPE, permit, and label rules
NFPA 855: The Standard for the Installation of Stationary Energy Storage Systems, governing location, separation, detection, ventilation, and suppression [https://anvilfield.com/field-guides/glossary/nfpa-855/]
Nip point: The in-running pinch where a belt meets a pulley, a chain meets a sprocket, or two rollers meet, that draws in and amputates
Nipple: Raceway 24 in or less between enclosures, allowed 60 percent fill and exempt from the more-than-three derating
Nitrogen purge: A low flow of dry nitrogen through the tube during brazing to displace oxygen and prevent internal oxide scale [https://anvilfield.com/field-guides/glossary/nitrogen-purge/]
NLC / LLLC: Networked lighting control, and luminaire-level control with a sensor in every fixture, rebate-eligible on the DLC list
NLGI grade: Grease consistency scale; NLGI 2 is the common soft-solid motor grade
NMAS: Nominal maximum aggregate size, one sieve above the first to retain over 10 percent; names the mix and sets the lift [https://anvilfield.com/field-guides/glossary/nmas/]
NMAS / t/NMAS: Nominal maximum aggregate size, and the lift-thickness-to-NMAS ratio that sets minimum lift
NMC: Lithium nickel manganese cobalt oxide: higher energy density, less thermally stable than LFP
No-load tap: Primary voltage-adjustment tap set with the unit de-energized, commonly 2.5 percent steps
No-load taps: Off-load primary connection points, commonly plus or minus 5 percent in 2.5 percent steps
NOAEL / LOAEL: No-observed and lowest-observed-adverse-effect levels, the human-exposure limits the design concentration is held against
NOC: Network operations center, the team and room that watch the IT and network layer, server and link health and service availability, as distinct from the physical plant.
Nominal max aggregate: Largest standard sieve size; coarse aggregate over 1-1/2 in is wet-sieved out before a slump test
Nominal max aggregate size: The largest standard sieve the coarse aggregate is graded to; drives water demand and member fit
Non-chloride accelerator: A set accelerator without chloride, used in reinforced and post-tensioned concrete to avoid corroding the steel [https://anvilfield.com/field-guides/glossary/non-chloride-accelerator/]
Non-combustible cabinet: A structure of masonry or galvanized steel stud with cement board, not wood, that carries the counter and resists heat and weather
Non-condensable: A gas such as air that will not condense in the system, raising head pressure until the vacuum removes it
Non-condensable gas: Air or other gas that leaks into a two-phase system and blankets the condenser, degrading heat rejection
Non-condensables: Air and moisture in the refrigerant circuit that blanket condenser tubes and raise condensing pressure and lift [https://anvilfield.com/field-guides/glossary/non-condensables/]
Non-conformance report (NCR): The document recording work that failed the spec, tracked through disposition, root cause, and close-out
Non-entry rescue: Retrieving an entrant from outside the space with a harness, retrieval line, and tripod or davit winch, with no one entering
Non-friable: Bound material that cannot be crumbled by hand when intact, split into Category I and II; releases fibers when cut, ground, or broken
Non-penetrating support: A block, sleeper, or stand that carries load on top of the membrane without piercing it
Non-potable: Water not safe or approved for drinking, covering reclaimed, graywater, and rainwater
Non-self-supporting ladder: A ladder that leans on a structure for support, such as a single or extension ladder
Non-shrink grout: Grout built so controlled expansion offsets shrinkage, holding contact under a plate; ASTM C1107 [https://anvilfield.com/field-guides/glossary/non-shrink-grout/]
Non-shunted tombstone: A lamp holder whose two contacts are not internally connected, required by most Type B tubes
Non-stock / special-order: A part ordered for a specific job rather than held on the truck
Noncoincident loads: Loads that cannot run at once, such as heat and AC, where only the larger is counted (220.60)
Noncondensables: Gases such as air that will not condense in the system, raising head pressure until evacuated out
Nonconformance report (NCR): The formal record of work or material that does not meet the requirement, tracked through disposition and corrective action to closure
Normally-open / normally-closed: The damper's position with no power, which sets how it fails
Not-to-exceed (NTE): A cap on time-and-material billing that the contractor cannot pass without further approval
Notched wedge: A tapered longitudinal joint with top and bottom notches, formed on the first pass to confine the edge and raise density
Notched wedge joint: A longitudinal joint with a tapered, notched edge that tends to compact more uniformly than a butt joint
Notched-wedge joint: A tapered longitudinal joint with small top and bottom notches, formed by a screed shoe to confine the first pass edge and densify the seam [https://anvilfield.com/field-guides/glossary/notched-wedge-joint/]
Notice of intent: A written warning that you will record a lien if the bill is not paid by a stated date; required in some states and a common collection tool.
NOWL: Normal operating water level on a steam boiler; the LWCO trips a set distance below it while water still covers the metal
NPDES discharge: A permitted discharge of water to surface waters under the federal pollutant discharge program
NPDES permit / SDWA: The NPDES discharge permit governs wastewater effluent under the Clean Water Act; the Safe Drinking Water Act sets MCLs for drinking water
NPS Preservation Brief 2: The National Park Service guidance on repointing mortar joints in historic masonry buildings
NPSH: Net positive suction head; available (NPSHa) must exceed required (NPSHr) at the suction to avoid cavitation
NPSH margin: The cushion NPSHa is held above NPSHr; set per the manufacturer and the application, not a fixed number
NPSHa: Net positive suction head available; the suction-side pressure margin the system delivers, above the water's vapor pressure, in feet [https://anvilfield.com/field-guides/glossary/npsha/]
NPSHa / NPSHr: Net positive suction head available from the system versus required by the pump; NPSHa must exceed NPSHr or the pump cavitates
NPSHr: Net positive suction head required; the suction head the pump needs at a given flow, read from the manufacturer's curve [https://anvilfield.com/field-guides/glossary/npshr/]
NPT: National pipe thread, the tapered thread sealed with PTFE tape or pipe dope, not by the threads alone
NRC vs CAC: NRC is sound absorbed in the room; CAC is sound blocked from passing over a partition into the next room
NRR: Noise Reduction Rating on hearing protection, a lab figure that is derated for real-world use [https://anvilfield.com/field-guides/glossary/nrr/]
NSF listing: Certification that foodservice equipment meets the NSF/ANSI sanitation standards for cleanable, food-safe construction, which the health code commonly requires
NSF/ANSI 53: Certification for point-of-use filters that reduce lead, both soluble and particulate
NSF/ANSI 61: The certification that a material in drinking-water contact does not leach contaminants above health limits [https://anvilfield.com/field-guides/glossary/nsf-ansi-61/]
NSPS Subpart IIII: 40 CFR Part 60 Subpart IIII, the federal standard for stationary CI engines
NTE (not-to-exceed): The cost cap a customer sets before fresh approval is required
NTEP: National Turfgrass Evaluation Program, the independent multi-state cultivar trials since 1981
NVP: Nominal velocity of propagation; how the tester converts signal time into length
NVR / VMS: NVR is a dedicated recording appliance for small to mid sites; VMS is server or cloud software that scales and integrates with other systems
O and P: Overhead and profit, the markup that turns direct cost into a price [https://anvilfield.com/field-guides/glossary/o-and-p/]
O terminal: Thermostat terminal that energizes the reversing valve in cooling, used by most manufacturers
O&M manual: Operation and maintenance documentation organized by system, with the installed equipment's model, serial, parts, and maintenance data
O&O rate: The all-in hourly machine rate, total ownership plus operating cost divided by productive hours
O&P: Overhead and profit, added on top of the direct job cost
O2 (oxygen): Leftover oxygen in the flue, a direct measure of excess air; about 20.9 percent in fresh air
OA / MA / RA: Outside air, mixed air, and return air, the temperatures the economizer decides on
OAC meeting: The owner-architect-contractor meeting, the formal progress and decision forum, usually weekly or biweekly during active construction
OBD: Opposed-blade damper at the device, for trim and shutoff, not for balancing the system
Objectionable current: Normal neutral current flowing on the equipment grounding system, caused by more than one neutral-to-ground bond
Obscuration per foot: How much smoke dims light over a distance, the unit the detector's sensitivity and alarm thresholds are set in
Observability: Seeing what the network is actually doing in detail, enough to answer why a job was slow, not just whether links are up
Occupancy vs vacancy: Auto-on/auto-off versus manual-on/auto-off; code often requires manual-on vacancy
OCP BBU shelf: The Open Compute Project Open Rack battery shelf, modular and redundant, feeding the 48V-class rack busbar
OCPD: Overcurrent protective device, the breaker or fuse whose rating sets the minimum EGC size [https://anvilfield.com/field-guides/glossary/ocpd/]
OCPP: Open Charge Point Protocol, the open language a networked charger speaks to a management platform
OCR: Optical character recognition, reading the amount and merchant off a receipt photo
OEO conversion: Optical-electrical-optical conversion, turning light into an electrical signal and back; what an OCS skips and a packet switch must do
Off-gas / vent gas: The flammable mixture a cell releases before and during runaway, detectable minutes before fire
Off-gassing: Hydrogen and oxygen released when charge current splits water in the electrolyte, rising with overcharge
Offset: A joint where two pipe sections no longer line up and catch debris [https://anvilfield.com/field-guides/glossary/offset/]
Offset and angular misalignment: Shafts parallel but off-center (offset) or meeting at an angle (angular); both are corrected with dial or laser alignment
Offset joint: A joint where one pipe section has shifted off the next, leaving a ledge
Offtaker: The heat buyer or user who takes the recovered heat, ideally nearby with year-round demand
OGFC: Open-graded friction course, a porous surface mix that drains water and cuts spray and noise
OH&P: Overhead and profit, the markup on a change; entitlement is recognized but the percentage is commonly set by the contract
Ohm: The unit of electrical resistance; ESD floor values run high and are written in scientific notation
Ohm and scientific notation: The resistance unit; ESD values run high, so 1.0 x 10^9 ohms is one gigohm and 1.0 x 10^6 ohms is one megohm
Oil analysis: The blood test of a machine: wear metals, contamination, and lubricant condition from an oil sample
Oil canning: Cosmetic waviness in the flat of a panel, not a structural defect or a leak
Oil logging: Oil that will not return collecting in the evaporator, filming the tubes and cutting capacity
Oil return: Keeping the compressor's oil circulating with the refrigerant and back to the crankcase
Oil separator: A discharge-line device that returns most oil to the crankcase near the source
Oil trap (P-trap): A U at the base of a riser that pools oil and slugs it up; inverted at the top to stop drain-back
Oil-canning: The popping flex of an unsupported panel under pressure, stopped by reinforcement
Oil-return velocity: The minimum vapor speed that drags oil back to the compressor; the controlling number on suction and hot-gas risers at minimum load
Oil/water separator: Tank that floats petroleum oil and settles grit out of wastewater before discharge; also oil separator or oil interceptor
OJT: On-the-job training, the paid hours an apprentice works under a journeyman doing real work
Old-technology aluminum: The early solid aluminum branch-circuit wire of roughly 1965 to 1973, the material this guide is about
OLTS: Optical loss test set, the light source and power meter pair used for Tier 1
OLTS / OTDR: Optical loss test set for Tier 1 end-to-end loss; optical time domain reflectometer for Tier 2 event-by-event traces
OM3 / OM4 / OM5: Laser-optimized multimode grades; OM3 and OM4 aqua at 850 nm, OM5 lime green wideband for SWDM
OM4 / OS2: OM4 is laser-optimized multimode for short reach; OS2 is low-water-peak singlemode for backbone and long high-speed runs
On-center (o.c.): The spacing distance measured between the centers of neighboring plants, typically set to mature width
On-center spacing: The distance from the center of one plant to the center of the next, which sets the plant count per square foot
On-site / behind-the-meter (BTM): Power generated at the data center, behind the utility meter, instead of bought from the grid
On-the-way text: An automated message sent when the crew is dispatched, with an arrival time and the technician's name, for trust and safety before the visit
One-shot / recharge: A gaseous system discharges once and is then unprotected until the cylinders are recharged and reconnected
One-third rule: Never remove more than a third of the grass blade height in a single mow
Open delta / wye: Three-phase buck-boost arrangements using two units (open delta) or three units (wye, four-wire only)
Open frame vs cabinet: A bare-post rack with no doors versus an enclosed box with doors and side panels
Open loop: A pump-and-discharge system that runs actual ground water through the unit and reinjects or discharges it
Open transition: Break-before-make transfer, with a brief dead interval as the load moves between sources
Open vs closed transition: Whether the motor is briefly disconnected during a wye-delta changeover (open) or kept energized (closed)
Open-face notch: A wide face cut, often 70 degrees or more, that keeps the hinge working through more of the fall
Open-graded: Single-sized aggregate or mix with the fines left out so the voids stay open and connected
Open-graded base: Clean, no-fines crushed stone that drains through itself; the basis of permeable construction
Open-items log: The running list of unresolved questions, decisions, and actions, carried meeting to meeting until each is done
OpenU (OU): The OCP Open Rack unit, 48 mm, on the wider 21 in Open Rack bay
Operating cost: The variable cost that accrues only when the machine runs: fuel, lube, wear parts, tires or tracks, repairs
Operating point: Where the pump curve crosses the system curve; the flow and head the pump actually delivers in that loop [https://anvilfield.com/field-guides/glossary/operating-point/]
Operating weight: The equipment weight full and running, the weight that drives the seismic force
Operator certification: The state license, by plant class, required to legally run a treatment plant's process
Opex: Operating expenditure: the recurring cost to run, dominated by energy, then maintenance, staff, water, and lease
OPIM: Other potentially infectious material, the body fluids and tissues beyond blood that the bloodborne pathogens standard also covers
OPR: Owner's project requirements, the measurable statement of what the owner needs the building to do, the yardstick for every test
OPR / BOD: Owner's project requirements and basis of design, the requirement and the design team's documented answer to it [https://anvilfield.com/field-guides/glossary/opr-bod/]
Optical arc-flash relay: An active mitigation system that trips on the light of an arc confirmed by current, clearing in milliseconds
Optical circuit switch (OCS): A switch that steers light from an input fiber to an output fiber as a held path, with no optical-electrical-optical conversion or packet processing
Optimal start: Starting equipment only as early as needed to reach setpoint by occupancy
Optimum moisture content (OMC): The moisture content at which a soil reaches its maximum dry density
Optional method: The 220.82 dwelling calculation, 100 percent of the first 10,000 VA and 40 percent of the rest
Optional standby (NEC 702): Owner-chosen backup for property and continuity, with no code-mandated transfer time
Or-equal / substitution: A request to install a product other than the one specified, with the burden on the contractor to prove it meets the spec
Orangeburg: Bituminized fiber pipe from roughly the 1940s to early 1970s that blisters and deforms
Order of precedence: The contract's stated hierarchy of which document governs when two documents conflict
Organic matter: Percent of decomposed material in the soil; drives water and nutrient holding, commonly 3 to 6 percent in good turf soil
Organic matter (OM): Decomposed plant and animal material in the soil, reported as a percentage; 2 percent or more is healthy
Orifice plate: The calibrated restriction that turns a pressure drop into an accurate leakage cfm reading
OS1 / OS2: Single-mode grades; OS2 is low-water-peak glass for long and outside-plant runs
OSDP: Open Supervised Device Protocol, the SIA standard for encrypted, supervised, two-way reader-to-controller communication, replacing legacy Wiegand
OSHA 1926.1153 / PEL: The construction silica standard; PEL is 50 micrograms per cubic meter as an 8-hour TWA, with a 25 microgram action level
OSHA 1926.62: OSHA's lead in construction standard governing worker exposure, with a 50 ug/m3 PEL and a 30 ug/m3 action level as 8-hour averages
OSHA 300 / 300A / 301: The recordable injury log, the annual summary, and the incident report under 29 CFR 1904
OSHA Subpart R: 29 CFR 1926 Subpart R, the steel erection standard covering anchorage, stability, connections, and fall protection
OSP: OSHPD, now HCAI, special seismic certification preapproval listing for qualified equipment
OTDR / loss budget: The instrument that maps splices and faults by distance, and the total allowed link loss in dB
Outdoor air (OA): Air brought in from outside to dilute indoor contaminants, the only air that ventilates
Outdoor counter material: A dense, weather-tolerant surface such as porcelain slab, granite, soapstone, or concrete; not laminate, marble, or engineered quartz
Outdoor kitchen: A built-in cooking and prep cabinet outdoors, combining structure, gas, electrical, plumbing, counters, and appliances in the weather
Outdoor reset: Control that lowers the supply water temperature as outdoor temperature rises, so the floor runs steady [https://anvilfield.com/field-guides/glossary/outdoor-reset/]
Outdoor-air damper: The damper that admits outdoor air for ventilation; stuck or closed, it is the most common HVAC IAQ fault
Outdoor-rated appliance: A grill, refrigerator, or burner listed for outdoor built-in use, with corrosion-resistant materials and sealed components; indoor units are not
Outlet control structure: The riser, orifice, and weir assembly that sets the release rate, often multi-stage for different design storms
Outrigger beam / counterweight / tieback: The cantilevered roof beam, the rated weights that hold its inboard end down, and the separate line tying it back to a sound anchor
Outriggers / cribbing: The extending legs and the bearing pads under them that keep the pump truck from tipping
Outriggers / stabilizers: Legs that extend the base for stability; only effective fully set on firm bearing
Outside plant (OSP): The outdoor part of the network, buried or aerial, from the central office out to homes and businesses
Outside-air fraction: The measured share of supply air that is outside air, the real check on a damper position
Over / under billing: Billed ahead of the work done (a liability) or behind it (financing the customer)
Over-protection / disbondment: Too much CP, causing hydrogen evolution, coating disbondment, and hydrogen embrittlement of susceptible steel
Overbilled (billings in excess of costs): Billed ahead of the work in place; cash in hand now but not yet earned and owed back in work
Overbilling: Billings in excess of earned revenue; a liability, since it is cash billed ahead of the work
Overburden: Everything above the membrane: drainage layer, filter fabric, growing media, and plants, plus any ballast and pavers [https://anvilfield.com/field-guides/glossary/overburden/]
Overflow / secondary drain: Code-required backup drainage set above the low point to cap water depth if the primary drains clog
Overflow drainage: The secondary drains or scuppers that carry water when the primary system is blocked
Overhead: The cost of running the company that cannot be billed to one job: rent, office staff, insurance, software, and the owner's management pay. [https://anvilfield.com/field-guides/glossary/overhead/]
Overhead allocation: The share of company-wide indirect cost loaded onto a job, per labor hour or as a percent of direct cost
Overhead door: A door that lifts overhead to clear an opening, counterbalanced by a spring so it can be lifted without its full weight
Overhead recovery: Collecting each job's share of overhead through the markup, so the cost of being in business gets paid across the year's work.
Overhead vs general conditions: Overhead is the whole-business indirect recovered through markup; general conditions are one job's indirect, recovered as job cost
Overlap (lap): Running the tarp so the upper section covers the lower and the up-slope edge tucks under existing roofing, so water sheds over the top and never under
Overlay / resurfacing: A thin cementitious topping bonded over existing sound concrete to renew or decorate the surface
Overload: The device that protects the motor from running too hot, set to 115 or 125 percent of nameplate FLA [https://anvilfield.com/field-guides/glossary/overload/]
Overload relay: Device that senses running current and trips the contactor on a sustained overload before the windings overheat
Overseeding: Sowing new seed into an existing lawn to thicken the stand and fill thin spots
Overspeed safety device: The independent mechanical brake, a parachute or block-stop, that clamps the mast if the platform descends too fast
Oversubscription: Provisioning more nameplate IT than the installed power could serve if everything ran at worst case at once [https://anvilfield.com/field-guides/glossary/oversubscription/]
Overturning moment: The load times the height of the post, the prying force the anchorage at the base must resist
Owner dependence: How much the business relies on the owner; high dependence is the biggest value killer at sale
Ownership cost: The fixed annual carry that runs whether the machine works: depreciation, cost of capital, taxes, insurance, storage
Owning and operating cost: Fixed owning cost plus variable operating cost, divided by hours worked, to get the cost per hour
Oxidizer: A gas like oxygen that does not burn itself but accelerates and intensifies the burning of other materials
Oxygen scavenger: A chemical such as sulfite that reacts with dissolved oxygen to stop it pitting the steel
Oxygen-barrier PEX: PEX tubing with an EVOH layer that blocks oxygen diffusion, required on closed systems to protect ferrous parts from rust
Oxygen-fuel separation: Storing oxygen at least 20 ft from fuel gas or behind a 5 ft, half-hour fire-rated barrier
P: Test static pressure in inches of water gauge, commonly the design pressure class
P (avg): The average force in the tendon over its length, after friction and seating losses
P / w (service load): The unfactored column load in pounds, or wall load in pounds per foot, the footing carries
P abs: Absolute pressure on the water at the suction source, in feet: atmospheric on an open system, fill pressure on a closed loop
P and K rating: Phosphorus and potassium reported low to optimum against a turf target, telling you whether to add them
P and P bonds: Performance and payment bonds, issued together, guaranteeing completion and payment to subs and suppliers
P vapor: Vapor pressure of the water at its operating temperature, in feet; it rises sharply with temperature
P-F curve / P-F interval: The failure path from potential failure (P, first detectable) to functional failure (F); the interval between is the window to act
P-T chart: Pressure-temperature chart for a specific refrigerant, converting a measured pressure to a saturation temperature
P-trap: The standard fixture trap, a sideways U with a horizontal arm to a vent, that self-scours
P-trap / inverted trap: A base trap that helps lift oil up a riser; an inverted top trap that stops oil draining back when the header is above the evaporator
P_elev: Static head loss lifting water to the highest fixture, about 0.43 psi per foot of rise
P_meter / P_bf: Pressure loss through the water meter and any backflow preventer at the design flow, from the device data
P_res: Minimum residual flowing pressure the worst fixture needs to operate, left on the budget
P_supply: Minimum daily service pressure at the source, in psi, the guaranteed low, not the peak
PACE: Property Assessed Clean Energy financing, repaid through an assessment on the property tax bill
Pachometer: A cover meter that uses an electromagnetic field to find shallow rebar and measure cover; steel only, not deep
Pack-back: Returning the cleaned and stored contents to the finished structure, reconciled and signed off
Pack-out: Inventorying and removing salvageable contents for cleaning and storage off site
Packaged vs split: Whole refrigeration circuit in one cabinet, versus an indoor unit and outdoor unit joined by a refrigerant line set
Packet loss: Packets dropped in the fabric, which forces a retransmit and stalls the synchronized collective the GPUs are waiting on
Packing: Braided rings squeezed around the shaft in a stuffing box; the older seal type, meant to weep a controlled drip
PACP: NASSCO's Pipeline Assessment Certification Program, the standard language for grading camera findings [https://anvilfield.com/field-guides/glossary/pacp/]
Pad / cleat guard: An individual friction device set in a staggered pattern to break the snowpack into smaller releases
Paging / PA: Public address: one source announced to many speakers in a zone or building, one direction, no reply
PAI: Permit authorizing individual, the trained person who surveys the area, sets the precautions and monitoring duration, and signs the permit
Panel replacement: Swapping the load center on the same service, keeping the existing amperage
Panelboard / load center: The dead-front assembly that splits a feeder into protected branch circuits; load center is the residential name
PAPA: Positive air pressure attenuator, an engineered device that absorbs positive pressure transients an AAV cannot relieve
PAPR: Powered air-purifying respirator; blower-fed, can be loose-fitting and beard-compatible
Par level (min/max): The target stock for a part, with a minimum that triggers reorder and a maximum that caps it
Parallel file system: Storage that stripes files across many nodes so they serve throughput in parallel, scaling bandwidth with node count
Parallel neutral path: Neutral current riding on the grounding system because the neutral is bonded to ground in more than one place; the source of nuisance trips and shock hazard
Parallel optics: A transceiver transmitting and receiving on multiple fibers at once, plugging into a native MPO
Parallel set: One conductor of each phase, plus neutral and equipment ground, run together as one circuit's worth
Parapet: The wall that extends above the roof at the edge of a low-slope building
Parking structure restoration: A planned program to stop chloride-driven corrosion and repair the damage, not just patch the spalled concrete
Part warranty: The manufacturer's coverage of a component against defects, from 1 to 10 or more years
Part-only warranty: Coverage that replaces the defective part free but pays nothing toward labor
Partial / full free cooling: Partial unloads the chiller while the economizer helps; full carries the whole load with the compressor off
Partial discharge: Localized insulation breakdown at a defect that erodes the insulation before it flashes over; tested online or offline
Partial discharge (PD): A tiny localized discharge in a void or defect under voltage, the mechanism that erodes insulation and a key termination diagnostic
Particulate / filtration: Suspended solids in the coolant, removed by full-flow and side-stream filters rated to the cold-plate channel size
PASS: Pull the pin, Aim at the base, Squeeze the handle, Sweep side to side
Pass-count map: A color map of how many times the drum covered each part of the mat, used to hold uniform coverage
Passing ability: The mix flowing through congested bars without blocking, read on the J-ring or L-box
Passivation: The protective iron-oxide film that forms on steel in high-pH concrete and stops corrosion
Passive chilled beam: A cooling-only beam with no primary air, cooling the space by natural convection alone
Passive RDHx: A rear door with no fans that relies on the server fans to push exhaust air through the coil
Passive vs active: Passive vents by stack effect with no fan; active adds a fan and is the reliable approach
Paste-over / cap seal: The epoxy band troweled over the crack face so injection builds pressure instead of leaking out
Patching: Repair of damaged fireproofing back to the listed thickness and density, or the rating is void at that spot
Pathway: The tray, conduit, raceway, ladder rack, or J-hook system that supports and routes the cable
Pavement ME / MEPDG: The mechanistic-empirical design method that models layer response and predicts distress over the life
Pavement preservation: A planned program of low-cost treatments on sound pavement to keep good roads good and delay reconstruction; not a structural repair [https://anvilfield.com/field-guides/glossary/pavement-preservation/]
Pay-if-paid: A clause making the owner's payment a precondition of the GC paying you
Payment bond: A surety bond posted on public and some private jobs that backs payment to subs and suppliers; on public jobs the bond claim replaces the lien. [https://anvilfield.com/field-guides/glossary/payment-bond/]
PBB / TMGB: Primary bonding busbar, one per building, bonded to the service grounding electrode system
PC (pressure-compensating): An emitter that holds constant flow across a range of inlet pressures, for slopes and long runs
PCC: Point of common coupling, the boundary between utility and customer where IEEE 519 applies
PCI: Pavement Condition Index, a 0 to 100 surface-condition rating under ASTM D6433 used to choose the treatment [https://anvilfield.com/field-guides/glossary/pci/]
pCi/L / action level: Picocuries per liter, the radon unit; 4 pCi/L is the EPA action level at which mitigation is recommended
PCS: Power conversion system, the inverter that moves energy between the battery DC and the building or grid AC, rated in kW [https://anvilfield.com/field-guides/glossary/pcs/]
PD: Powered device, the camera, AP, or controller drawing power at the far end
PDI: Plumbing and Drainage Institute, source of the G101 interceptor rating standard
PDI WH-201: The Plumbing and Drainage Institute standard for arrestor certification and fixture-unit sizing, sizes A to F
PDU: Power distribution unit; here the floor PDU with a transformer and panels, not the rack PDU strip [https://anvilfield.com/field-guides/glossary/pdu/]
Peak attenuation: Cutting the highest flow rate leaving the site by storing water faster than the outlet releases it, the core job of a basin
Peak shaving: Trimming the grid draw during the highest-demand hours by supplying part of the load from on-site generation or batteries [https://anvilfield.com/field-guides/glossary/peak-shaving/]
Pedestal: The adjustable column, base plate plus threaded tube and head, carrying axial load from the panels to the slab [https://anvilfield.com/field-guides/glossary/pedestal/]
Pedestal / stringer: The vertical column and the horizontal member that carry an access floor's load and lock its grid
Pedestal axial load: The straight-down load the pedestal column carries to the slab
PEL: Permissible exposure limit, near 90 dBA over 8 hours, the OSHA enforced ceiling for the average
Penetrant: The item passing through, here the pipe, by material and size
Penetrating sealer: A reactive or repellent sealer that soaks into the concrete and works below the surface, leaving no film
Per diem: A daily allowance for being away from home, split into lodging and meals and incidental expenses
Perc rate: How fast soil absorbs water, the measure that decides whether a dry well or infiltration outlet works
Percent complete: The portion of a line finished to date, most defensible when tied to a countable quantity rather than an eyeball [https://anvilfield.com/field-guides/glossary/percent-complete/]
Percent fill: Sum of conductor areas as a percentage of the conduit's interior cross-sectional area; capped by NEC Chapter 9, Table 1
Percent of Gmm: In-place density as a percentage of Gmm; 100 minus it is roughly the air-void content
Percent solids by volume: The fraction of the wet coating that remains as cured film; the wet-to-dry multiplier, from the data sheet
Percentage of completion: Accounting method that recognizes revenue as work is earned, commonly measured cost-to-cost
Percentage-of-completion: Recognizing revenue as the job progresses, commonly on the cost-to-cost basis; a method-and-CPA decision
Perched water table: Water trapped above an abrupt texture change, the bathtub effect under thin topsoil on compacted clay [https://anvilfield.com/field-guides/glossary/perched-water-table/]
Percolation / soil evaluation: The perc test measures how fast soil drains in minutes per inch; the soil evaluation reads texture, limiting layer, and water table to set feasibility and design
Perforated backing: Turf backing with drainage holes; fully permeable backing drains across the whole surface for higher flow
Perforated tile: A floor panel with openings that lets plenum air up into the cold aisle
Performance bond: Guarantees you complete the work per the contract, usually for the full contract amount
Performance ratio (PR): Actual energy output divided by the energy expected from measured irradiance and rated capacity, the headline efficiency metric, referenced to IEC 61724
Pergola: Posts and crossbeams with an open or louvered roof, for partial shade and airflow, free-standing or attached
Perimeter control: Fencing, gates, and one controlled entrance that limit where the site can be entered and let you see who comes and goes
Perimeter surface: The walking area within 3 ft of the inside wall, bonded as part of the plane
Perimeter vs interior detection: Perimeter catches entry at doors and windows; interior catches movement inside with motion detectors; layered so each covers the other's miss
Periodic inspection: The annual federal inspection of a commercial motor vehicle under 49 CFR 396.17, at least once every 12 months
Perm: The unit of water vapor permeance, measured by ASTM E96; lower perm resists diffusion more [https://anvilfield.com/field-guides/glossary/perm/]
Perm / permeance: The measure of how readily water vapor passes through a material; lower is a better barrier
Permanent link: The fixed installed cabling that TIA-606 records describe, distinct from the patch cords the cross-connect record tracks [https://anvilfield.com/field-guides/glossary/permanent-link/]
Permanent set: The deformation that remains in the panel after the load is removed; the floor never recovers it
Permanent suction line: The center bottom tube on the valve that always returns refrigerant to the compressor
Permeable / porous pavement: A surface that passes water through it into a stone reservoir; porous usually means through the body (asphalt, concrete), permeable through the joints (pavers)
Permeable base / OGDL: Open-graded drainage layer under the surface that drains the whole footprint to a collector or daylight
Permeation grouting: Injecting low-viscosity grout into the pores of granular soil to bind the grains and cut permeability
Permit authorizing individual (PAI): The person under NFPA 51B who authorizes hot work, confirms the area is safe, and sets any extended monitoring
Permittivity vs transmissivity: Permittivity is water flow across the fabric; transmissivity is water flow in the plane of the fabric for drainage.
Perpetual pavement: A thick section designed so fatigue never reaches the bottom of the asphalt; renewed by resurfacing
Persistence: Holding the RCx savings over time instead of letting the building drift back [https://anvilfield.com/field-guides/glossary/persistence/]
Personal gas monitor / 4-gas: A worn detector reading oxygen, combustible gas at the LEL, carbon monoxide, and hydrogen sulfide
Pervious concrete: Open-graded, near-zero-fines concrete with interconnected voids that water drains through; also porous or permeable concrete
PEX: Cross-linked polyethylene, a flexible plastic potable water tube in types a, b, and c
PF1 / theta1: Present power factor and its phase angle, before correction
PF2 / theta2: Target power factor and its phase angle, commonly 0.95 to 0.98
PFAS: Per- and polyfluoroalkyl substances, the fluorinated chemistry behind most two-phase fluids, under heavy regulatory and supply pressure [https://anvilfield.com/field-guides/glossary/pfas/]
PFC: Priority flow control, a link-layer pause that stops a traffic class to prevent drops but can cause head-of-line blocking and stalls [https://anvilfield.com/field-guides/glossary/pfc/]
PG grade: Performance grade of the binder, high minus low temperature in Celsius, like PG 64-22
PG25: A roughly 25 percent propylene-glycol-and-water coolant with an inhibitor package, a common secondary-loop fluid [https://anvilfield.com/field-guides/glossary/pg25/]
pH: Surface alkalinity on a 0 to 14 scale; fresh concrete commonly reads 12 to 13 [https://anvilfield.com/field-guides/glossary/ph/]
Phase: One of the three voltages in a three-phase system, spaced 120 electrical degrees apart, labeled A, B, C or L1, L2, L3
Phase angle: Angular difference between incoming and bus voltage at the instant of close, near zero
Phase balance: Spreading load evenly across the three phases so no phase overloads and neutral current stays low [https://anvilfield.com/field-guides/glossary/phase-balance/]
Phase imbalance: Uneven load across the three phases, which strands capacity on the lightly loaded phases
Phase rotation (sequence): The order the phases peak, A-B-C, which sets motor direction; swap two lines to reverse
Phase rotation / phase sequence: The order the three phases reach peak voltage, ABC or ACB, which sets motor direction
Phase sequence: Rotation order of the three phases, A-B-C, which must agree on both sides
Phase voltage: Voltage across one winding; in a wye this is the line-to-neutral value
Phase-monitor relay: A relay that trips the control circuit on reverse sequence, phase loss, or imbalance
Photo eye vs sensing edge: A photo eye is a non-contact beam (Type B1); a sensing edge is a contact pressure strip (Type B2)
Photocell: Light sensor that turns the display on at dusk and off at dawn, adjusting as the days shorten
Photogrammetry: Building a point cloud from many overlapping photographs, cheaper and full color, with softer geometry than lidar
Photogrammetry / orthomosaic: Stitching overlapping aerial photos into a geometrically corrected, measurable map and a 3D model of a site or structure.
Physical / gradation segregation: Separation of coarse from fine aggregate, leaving stone-rich or sand-rich areas
PI (polarization index): Ratio of the ten-minute to one-minute insulation-resistance reading; above 1.0 is the NETA floor
Pick radius: The horizontal distance from the crane's center of rotation to the load, which sets the rated capacity for that lift
Pickup / dropout: The voltage and frequency thresholds at which the controller accepts or rejects a source
Pickup and delay: The current at which a function starts to act and the time it waits; the two settings that fit a curve between the load below and the source above
Pickup and time delay: The ground current that triggers the trip and the deliberate wait before it acts
PICP: Permeable interlocking concrete pavement; open-graded stone layers that infiltrate water instead of shedding it [https://anvilfield.com/field-guides/glossary/picp/]
PICV: Pressure independent control valve, which holds a preset flow regardless of differential pressure within its control range [https://anvilfield.com/field-guides/glossary/picv/]
PID: Proportional-integral-derivative, the math that tunes a modulating control loop
PID / degradation: Potential-induced degradation, a voltage-driven string loss, against normal aging of roughly 0.4 to 0.5 percent per year over the module's life
PID / hunting: Proportional-integral-derivative control of modulating outputs; hunting is the oscillation of a mistuned loop around setpoint
Piece mark: The unique stamp on each member that ties it to its place on the erection drawing
Pigtail: A short copper conductor added to the aluminum with a listed connector so copper lands on the device [https://anvilfield.com/field-guides/glossary/pigtail/]
Pile height: The length of the turf fiber in inches, measured from the backing to the blade tip
Pilot solenoid: Small electric coil that shifts a pilot valve, letting system pressure move the main slide
Pinned / unpinned: Male (two guide pins) and female (two holes); a mate needs exactly one of each for ferrule alignment
Pinpointing: Finding the exact spot on the ground, usually by thumping and listening
Pipe boot: A prefabricated membrane cone that flashes a round pipe, welded or bonded at the base and clamped at the top
Pipe bursting: Replacing a pipe by pulling a bursting head through it that shatters the old pipe and pulls in new HDPE
Pipe-clamp probe: A thermocouple or thermistor strapped to a refrigerant line; accuracy and insulation from ambient air decide superheat and subcooling
Pipeline: Every lead sorted by stage, commonly new, quoted, won, and lost
PIR / dual-tech motion: PIR senses a moving heat signature; dual-tech adds microwave and alarms only when both agree, which cuts false alarms from HVAC and sun
PIR / ultrasonic / dual-tech: Heat-motion line-of-sight, sound-echo fine motion, and both combined to cut false trips
Piston / cup: The molded cup that meters a piston flushometer; more tolerant of dirty water than a diaphragm.
Pitch / slope: Rise over run in inches per 12 in, written like 6:12, which sets the slope factor
Pitch diameter (PD): The effective diameter where the belt rides in the groove, used for the speed ratio
Pitch pan: A pourable sealer pocket flashed around an odd penetration and filled with sealant; the last-resort detail
Pitch pocket: A sealant-filled box sealing an odd-shaped penetration; the filler shrinks and needs topping on a schedule
Pitch pocket / pourable pocket: An open metal collar around an irregular penetration filled with pourable sealer; a maintenance item and last resort
Pitless adapter: The fitting that takes water out of the casing horizontally below the frost line, replacing the old well pit
Pitot traverse: A grid of velocity-pressure readings across a duct, averaged to get true average velocity and then airflow
Pixels per foot (ppf): Horizontal pixels landed on each foot of the scene at the target distance; the metric that decides whether footage is usable
Placement: Getting fresh concrete into the forms and around the reinforcement near its final position
Placement temperature: The air and surface or base temperature at the time of paving; many specs require both above the minimum and rising
Placing drawings: The detailer's plans and sections showing every bar set in place and tagged with its mark
Planarity / flatness tolerance: The allowed surface deviation under a straightedge, commonly 3 mm under 1 m and 6 mm under 4 m
Plant coverage: The percentage of the media surface the intended plants cover, commonly targeted near 80 to 90 percent within about two years
Plant factor / water budget: A plant's water use as a fraction of reference ET, used in ordinances like MWELO to cap a project's landscape water
Plant health care (PHC): A proactive program of scheduled inspection and care that keeps plants healthy by managing soil, roots, water, and nutrition, with pest control as one part
Plant schedule: The table on a planting plan listing each plant by botanical name, size, quantity, spacing, and condition
Plant sequencing: The control logic that decides how many chillers run, which ones, and at what setpoints, as the load moves
Plant total: Compressors plus chilled-water and condenser pumps plus tower fans, the kW that actually pays the bill
Plant warranty: A priced promise to replace plants that die within a set period, bounded by written exclusions
Plaster start-up: The procedure for a new plaster or aggregate finish: a continuous fill, frequent brushing, and careful chemistry through the first days so the curing surface does not stain or etch.
Plastic settlement crack: An early crack over the top bars where fresh concrete settles around the reinforcement
Plastic shrinkage: Shrinkage of the surface while the concrete is still plastic, driven by evaporation outpacing bleed
Plastic shrinkage crack: An early surface crack opened in the first hours when evaporation outruns the bleed rate [https://anvilfield.com/field-guides/glossary/plastic-shrinkage-crack/]
Plastic shrinkage cracking: Cracks in fresh concrete when surface evaporation outruns the bleed rate, drying and shrinking the top before it sets
Plastic-shrinkage cracking: Early-age surface cracking while concrete is fresh, the job micro fibers control
Plasticity index (PI): The range of moisture over which a soil is plastic; high PI means a plastic clay
Plate-and-frame heat exchanger: Stacked corrugated plates that pass heat between the tower water and the chilled-water loop without mixing them
Plateau: The flat part of the resistance-versus-distance plot that confirms a valid fall-of-potential reading
Plenum: The pressurized underfloor air path that distributes cooling air, and any contamination loose in it [https://anvilfield.com/field-guides/glossary/plenum/]
Plenum (CMP/CL2P/FPLP): The cable rating required in air-handling spaces; passes a flame and smoke test in moving air
Plenum / AHU: Plenum is the supply or return box at the air handler; AHU is the air-handling unit
Plenum fan: An unhoused centrifugal fan that discharges into the cabinet plenum rather than a scroll
Plenum pressure: The static under the raised floor that lifts air through the tiles; commonly near 0.05 in. wg
PLHCP: Physician or other licensed health care professional who performs the respirator medical evaluation
PLS: Pure live seed, the viable germinating fraction of a seed lot, the basis for the spec rate
Plug: A small container-grown native plant, faster to establish than seed and placed by hand
Plug / blockage: Concrete that stops moving and jams the line, shown by pressure climbing as flow stops
Plug-in busway: Busway with tap openings at intervals so plug-in units can draw power along the run
Plug-in unit: A bolt-on or stab-in tap, often a fused switch or breaker, that clamps onto plug-in busway to feed a branch
Plug-in unit / bus plug: A breaker or fusible switch that clamps onto plug-in busway to tap a load
Plumbing fixture: A device connected to the water system that delivers water for use or receives waste, such as a toilet, lavatory, sink, urinal, shower, or drinking fountain
Plumbing rough: The main drains, returns, skimmers or gutter, and supply lines set and pressure-tested before the shell, so the shotcrete encases them in the structure.
Plumbing-up: Pulling the frame true with guys and come-alongs to within AISC 303 tolerance before connections are finalized
Plus or minus 7 percent: The common acceptance band for measured versus calculated elongation, per ACI 318 and PTI
Plus/minus 400 V: A DC bus referenced 400 V each side of a center point, 800 V rail to rail, which lowers the touch voltage to either rail
Ply / ply felt: A reinforcing sheet of organic or fiberglass felt; the layers built up into the membrane
PM: Preventive or planned maintenance, the scheduled servicing done on an interval rather than after failure
PM / PdM: Preventive maintenance on a schedule; predictive maintenance driven by condition data and trending
PM compliance: Percentage of scheduled PM completed on time within its window; the program's core metric
PM program: The full scheduled and condition-based maintenance regime for the critical power and cooling plant
PM2.5: Fine particulate up to 2.5 microns, including smoke and combustion soot, the fraction that penetrates deepest
PM2.5 / PM10: Particulate matter 2.5 and 10 microns and smaller, the fine and coarse fractions, reported in ug/m3
Pmax: Maximum lateral pressure of fresh concrete on the form, in psf
PMR / IRMA: Protected membrane or inverted assembly, with the insulation and ballast placed on top of the membrane
Pneumatic test: A pressure test using air or gas, allowed only when hydrostatic is impractical, because compressed gas stores far more energy and fails dangerously
PO (purchase order): A document authorizing a buy against a job, naming the items, the agreed price, and a tracking number [https://anvilfield.com/field-guides/glossary/po-purchase-order/]
PoE: Power over Ethernet; power and data on one cable, in classes af (about 15.4 W), at (30 W), and bt (60 to 90 W), to 100 m [https://anvilfield.com/field-guides/glossary/poe/]
POE oil: Polyolester oil for HFC and A2L refrigerants, hygroscopic, replaces mineral oil from the R-22 era
Point cloud: A dataset of millions of measured 3D points (X, Y, Z, often color and intensity) forming a dimensional shell of every visible surface [https://anvilfield.com/field-guides/glossary/point-cloud/]
Point of no pressure change: The expansion tank connection, whose pressure the pump cannot change; tie it near the pump suction and pump away from it [https://anvilfield.com/field-guides/glossary/point-of-no-pressure-change/]
Point tagging (Haystack / Brick): Standardized metadata on each point and equipment so analytics rules find and reuse across buildings
Point-of-entry / point-of-use: Whole-building treatment at the service versus single-fixture treatment, usually under a sink
Point-of-use valve: Local valve at or near the fixture (ASSE 1070 or 1016) that sets and caps the delivered temperature
Point-to-point: Verifying each physical point one at a time so the field device matches the BMS value and each output moves the right equipment
Poisson effect: The pressure-driven shortening of HDPE that can pull an unrestrained transition joint apart
Polarity: The end-to-end fiber mapping (methods A, B, C) that ensures transmit lands on receive; wrong polarity, no link [https://anvilfield.com/field-guides/glossary/polarity/]
Polarization index (PI): Ratio of the 10-minute to the 1-minute reading; above about 2 is commonly good [https://anvilfield.com/field-guides/glossary/polarization-index-pi/]
Pollinator plant: A plant that provides nectar and pollen for adult pollinators across the season
Polymer-modified binder: Asphalt cement stiffened with polymer to widen the working temperature range; a bumped PG grade
Polymeric sand: Joint sand with a binder that hardens when wetted; resists washout but hazes if installed wet or dirty [https://anvilfield.com/field-guides/glossary/polymeric-sand/]
Polyurethane injection: Flexible, water-reactive injection that foams and seals an active or leaking crack
PON / OLT / splitter / ONT: Passive optical network: the head-end OLT, the passive splitter, and the ONT at the home
Ponding: Water standing on the roof more than about 48 hours after rain, an aging accelerant and common warranty exclusion [https://anvilfield.com/field-guides/glossary/ponding/]
Ponding instability: Progressive deflection where water weight deflects the deck, which holds more water, which deflects further [https://anvilfield.com/field-guides/glossary/ponding-instability/]
Ponding water: Water standing on a low-slope roof more than 48 hours after rain in drying weather, per NRCA
Pondless: A feature with no standing water; it recirculates into a hidden gravel or matrix basin
Pool circulation: Pulling the water from the main drain and skimmers through the pump, filter, and heater and back through the returns, continuously
Popout: A conical hole with fractured aggregate at the bottom, from unsound, reactive, or frozen aggregate
Porous / permeable asphalt: Full-depth open pavement over a stone reservoir for stormwater infiltration
Porous vs non-porous: Porous materials like drywall and insulation are removed; non-porous like studs, metal, and glass are cleaned
Positive displacement: Compression by trapping a fixed volume of vapor and shrinking it; recip, scroll, screw, rotary
Positive drainage: Grade that falls away from a structure and toward an outlet, so water sheds instead of ponding or running back [https://anvilfield.com/field-guides/glossary/positive-drainage/]
Positive pressure room: A room held above its surroundings so clean air flows out, protecting the patient from the room (OR, PE)
Positive response: Each utility's posted answer confirming whether it marked the dig area or found no conflict
Positive side: The exterior, water-bearing face of the wall; the preferred side to waterproof
Post anchor / standoff base: An uplift-rated base that holds the post down and stands it off the concrete so the end grain does not rot
Post anchorage / base plate: The connection of the post to the structure that carries the rail load and the overturning moment
Post-emergent: Herbicide that kills weeds already growing, usually spot-applied [https://anvilfield.com/field-guides/glossary/post-emergent/]
Post-installed anchor: Anchor placed in hardened concrete in a drilled hole, mechanical or adhesive [https://anvilfield.com/field-guides/glossary/post-installed-anchor/]
Post-tension: Stressing tendons after the concrete has cured, putting the slab into compression
Post-tension (PT): Tensioned steel tendons in a slab; cutting one releases stored energy explosively
Post-tension tendon: A high-strength strand stressed to load the slab in compression; cutting one releases stored energy and weakens the structure
Post-tension tendon corrosion: Corrosion of stressed high-strength strand in PT slabs, from lost grease or void grout, that can fail suddenly; specialty work
Post-work monitoring: The period after the fire watch ends during which the area is checked for smoldering fire, set by the PAI to the risk
Pot life: The working time after mixing A and B before the resin is too thick to place
Potential change order (PCO): A priced proposal for a change, submitted for approval before it becomes a change order
Potential to emit (PTE): The emissions an engine could produce at its permitted hours, the basis for major-source status
Potholing / daylighting: Hand or vacuum digging to expose a line and verify its exact location and depth
POTW: Publicly owned treatment works, the municipal sewage plant the building discharges to
Pounds per hour: Sheet-metal labor productivity, the duct weight divided into hours of fabrication or install
Pourable sealer pocket: A metal or molded box flashed to the roof and filled with pourable sealant; the last-resort penetration detail, also called a pitch pocket or pitch pan
Power budget: Transmitter power minus receiver sensitivity, the loss the optics tolerate
Power cabinet vs dispenser: In a split architecture, the central rectifier cabinet against the stall unit with the connector and cable
Power capping: A hard limit on how much a device, rack, or row can draw, enforced by throttling before the budget is exceeded
Power commit (kW): The power capacity you reserve and pay for, whether or not your gear draws it
Power density: Electrical load in a footprint, usually kilowatts per rack, also per row or square foot
Power factor: Real power divided by apparent power, 0 to 1, low when the load is reactive or distorted [https://anvilfield.com/field-guides/glossary/power-factor/]
Power factor (PF): Ratio of kW to kVA; gensets are commonly rated at 0.8 lagging [https://anvilfield.com/field-guides/glossary/power-factor-pf/]
Power factor / dissipation factor: Insulation loss as a fraction of charging current, a condition test on larger units
Power factor / tan delta: AC test of insulation loss; a rising value signals aging, moisture, or contamination
Power inlet: A flanged inlet, not an outlet, mounted outdoors so the generator cord plugs in with no exposed energized parts
Power module / skid: Prefabricated electrical plant: switchgear, transformer, UPS, transfer switches, and distribution
Power shelf: Centralized rectifier shelf that converts facility AC to the rack DC bus, replacing per-server power supplies, usually N+1
Power volatility / spike: Large, fast swings in draw, idle to full in milliseconds, characteristic of AI GPU workloads
Power vs energy: Power is a short hard burst (ride-through); energy is sustained output over hours (autonomy and grid services)
Power-vented / Category III: A gas unit with a powered vent that pushes flue products out, often a sidewall, against positive pressure
Powered anode: Impressed-current titanium rod that protects the tank without being consumed
Pozzolanic reaction: The slow lime-clay reaction at high pH that forms cementitious bonds and long-term strength
PP / PVDF / CPVC: Chemical-resistant plastics used for acid-waste pipe, each suited to different chemistry
PPA: Power purchase agreement, a long-term contract to buy the output of a generation project
PPC: Percent Plan Complete, the count of tasks finished as promised divided by tasks promised for the week [https://anvilfield.com/field-guides/glossary/ppc/]
PPC (percent plan complete): Completed commitments divided by committed, times 100, measuring how reliable the planning system is, not crew speed
PPE category: A table-method tier, 1 to 4, each with a minimum arc rating of 4, 8, 25, and 40 cal/cm2
PPE category (1 to 4): The table-method classification with minimum arc ratings of 4, 8, 25, and 40 cal/cm2
pPUE: Partial PUE, the same ratio for a defined subsystem or zone within a stated boundary
PQR: Procedure qualification record, the tested evidence the WPS is built on
PR: Precipitation rate, the depth a zone applies per hour in inches per hour, measured or calculated [https://anvilfield.com/field-guides/glossary/pr/]
PRCS: Permit-required confined space: a confined space that also holds a serious hazard such as bad air, engulfment, or entrapment
Pre-action: A sprinkler system whose pipe stays dry until a detection event opens a valve, so a damaged head does not leak water [https://anvilfield.com/field-guides/glossary/pre-action/]
Pre-action system: Dry system whose valve is released by the fire alarm panel, keeping water out of the pipe until a fire is confirmed
Pre-charge: The air pressure on the sealed side of the tank, set to match the system static pressure before the tank is connected [https://anvilfield.com/field-guides/glossary/pre-charge/]
Pre-emergent: A herbicide that stops seed from germinating, which also kills new grass seed, so it conflicts with overseeding [https://anvilfield.com/field-guides/glossary/pre-emergent/]
Pre-emergent / post-emergent: An herbicide that stops weed seed before it germinates versus one that kills a weed already growing
Pre-engineered metal building (PEMB): A steel building system the manufacturer engineers and fabricates as a kit of rigid frames, secondary, bracing, and panels, shipped to the site to erect
Pre-slope: The sloped bed built under a traditional liner so the liner drains to the weep holes
Pre-sloped channel: A trench-drain section with built-in fall so the invert drops toward the outlet
Pre-task plan (PTP): The daily living hazard plan a crew completes for the actual conditions that morning, derived from the JHA or AHA
Pre-task plan / FLRA: The crew's field-level risk assessment of today's specific work and conditions, done before the task starts
Pre-wetting: Soaking the aggregate before batching so it does not steal mix water or lose slump
Preaction system: Dry pipe with water held back until fire detection (single- or double-interlock) acts; used for sensitive contents
Precast: Concrete cast to its final shape at a plant, cured, hauled, and set by crane on site
Precharge: The air pressure on the dry side of the expansion tank, set to the cold fill pressure before the loop is filled
Precipitation rate: The depth a zone applies per hour, in inches per hour, used to set run time
Precipitation rate (PR): Application depth in inches per hour, measured by catch can or calculated by the 96.25 formula [https://anvilfield.com/field-guides/glossary/precipitation-rate-pr/]
Preconstruction: The planning phase before construction, where the team prices the design, checks constructability, value-engineers, schedules, and locks the budget.
Predictive maintenance (PdM): Condition-based maintenance triggered by measured data (IR, vibration, oil, ohmic) before failure
Predictive twin: A connected twin plus simulation that forecasts behavior and runs what-if scenarios
Prefabricated vs modular: Prefabricated means built off site in a plant; modular means designed in repeatable blocks that scale by addition
Preliminary notice: The early notice (also called prelien notice or notice to owner) sent near the start of a job to preserve the right to lien; required in many states. [https://anvilfield.com/field-guides/glossary/preliminary-notice/]
Prelocation: Finding the distance to the fault from one end, before pinpointing
Prequalification: The documented screen of a contractor's financial, safety, bonding, experience, and reference standing, run before a bid is accepted [https://anvilfield.com/field-guides/glossary/prequalification/]
Preservation / rehabilitation / reconstruction: Protect sound pavement, restore fair-to-poor pavement, rebuild failed pavement
Press fitting: A fitting with an O-ring that a powered tool crimps onto the tube, no flame, with a witness mark for full insertion
Pressure cascade: Stepped room pressures holding each cleaner room positive to the dirtier one, clean-to-dirty flow
Pressure class: The operating static the duct is built to hold, in inches of water gauge, positive or negative [https://anvilfield.com/field-guides/glossary/pressure-class/]
Pressure dew point: Temperature at which the compressed air would start to condense; the dryness rating
Pressure drop: Pressure lost to the pipe, fittings, and treatment between compressor and tool [https://anvilfield.com/field-guides/glossary/pressure-drop/]
Pressure relief vent (PRV): A vent that opens only during the discharge pressure spike so a sealed room is not damaged
Pressure switch: The safety that proves the inducer is moving air before the gas valve can open
Pressure switch (well): The control that starts and stops a well pump at a cut-in and cut-out, commonly 40/60 psi, with the tank pre-charged just below cut-in
Pressure washing: Cleaning hard, durable surfaces with high-pressure water, commonly 2,500 to 4,000 PSI, that mechanically blasts dirt off
Pressure zone: A vertical slice of a building served as one pressure group
Pressure-dependent: A box with no flow sensor that commands a damper position only, so airflow rides with duct static
Pressure-equalized rainscreen: A drained, vented glazing pocket that equalizes air pressure so water is not driven in, then weeps out what gets past the outer seal.
Pressure-independent: A VAV box with a flow sensor that holds its airflow setpoint regardless of upstream duct pressure changes
Pressure-injection injury: A high-pressure stream puncturing skin and injecting fluid into tissue, a surgical emergency that looks minor at first
Pressure-regulating valve: A listed device that holds a hose valve outlet to a safe pressure under flow
Pretensioned joint: A joint with the bolt installed to a specified minimum tension by an RCSC method
Pretreatment: Treating waste to meet the sewer authority's limits before discharge to the public works
Pretreatment permit: Authorization from the sewer authority setting the oil and sediment limits, sampling, and records for the discharge
Prevailing wage: The locally determined base hourly rate plus fringe required for each worker classification on covered public construction [https://anvilfield.com/field-guides/glossary/prevailing-wage/]
Preventive / curative: An insecticide or fungicide applied ahead of the pest or disease versus one applied after it is active
Preventive maintenance (PM): Scheduled maintenance on a calendar or runtime interval, performed before failure, on the OEM basis
Preventive vs corrective maintenance: Planned work on good pavement before a deficiency versus reactive work after a deficiency appears
Price book: The menu of priced tasks, each built from book labor hours, parts, and markup
Primary / secondary loop: Facility water (FWS) on the building side, technology cooling system (TCS) coolant on the clean rack side, separated by the CDU heat exchanger
Primary air: The ducted, dehumidified ventilation air supplied to an active beam, which also drives the induction
Primary and non-contributory: An endorsement making your policy pay first, before the other party's policy
Primary drainage: The drains or scuppers that carry the normal design storm off the roof
Primary FLA: Rated current on the primary side, off the primary voltage, sizes the primary feeder and device
Prime / continuous power: A source rated to run as the normal supply for long or unlimited hours, not just standby backup
Prime coat: An asphalt material sprayed on a granular base to bind and seal it and bond the first asphalt layer
Priming: Coating the line with grout or slurry ahead of the concrete so it slides instead of plugging
Principal / obligee / surety: The contractor who is bonded, the owner protected by the bond, and the company backing the contractor
Print legend: The text printed along the jacket: maker, size, type, rating, and footage marker
Priority service: The member perk of going to the front of the schedule ahead of non-agreement customers
Pro-rated warranty: Coverage that pays a declining share of the part cost as the unit ages
Probable demand: The diversified peak flow in gpm from the WSFU total read off the Hunter demand curve, not the sum of fixture flows
Process air: The airstream being dried and delivered to the space or duct
Process piping: Pipe systems carrying process fluids, chemicals, gases, and steam in a plant at pressure and temperature, under ASME B31.3
Proctor / percent compaction: A lab test of maximum dry density and optimum moisture; field fill is compacted to a percentage of it
Proctor density: The lab maximum dry density a soil or aggregate compacts to; base targets are a percent of it, commonly 95
Production derate: The drop in pounds per day from rated ideal conditions to the real higher air and water temperatures of the room
Production rate: Units of work installed per labor hour, such as 25 lf formed per hour, or its inverse, hours per unit [https://anvilfield.com/field-guides/glossary/production-rate/]
Productive hours: The hours the machine actually works in a year, from the meter, not the calendar or a hoped-for figure
Productivity factor: Earned hours divided by actual hours; above 1.0 the crew beats the budget, below 1.0 it loses (confirm which way your report runs)
Products of combustion / flue gas: The exhaust off a gas burner, carbon dioxide and water vapor when clean, carbon monoxide when not
Profit fade: The estimated job margin dropping from one WIP update to the next; an early warning a job is going bad
Prohibited practices: Methods banned on lead paint: open-flame burning, power sanding or grinding without HEPA, heat guns above about 1100 degrees F, and dry scraping or sanding beyond small areas
Project indirect cost: Cost tied to the project but not to a single work item; the same idea as project overhead or job overhead
Prompt payment law: State statutes setting payment and retainage release deadlines and interest for late or wrongful withholding; nearly every state has one and the details differ.
Proof of work: A photo that backs a billed item, milestone, or completed scope, answering whether the work was actually performed
Proof packet: The single reviewable record that proves a scope was installed, tested, and accepted: the photos, tests, checklists, punch closeout, material records, and signoffs, tied to a location
Proof roll: Driving a loaded truck over the subgrade to find soft spots by rutting, deflection, or pumping
Proof rolling: Driving a heavy loaded vehicle over the surface to reveal soft, pumping, or rutting areas
Proof-roll: A loaded pass to find soft subgrade; on a permeable section it can itself compact the infiltrating soil, so it is often prohibited [https://anvilfield.com/field-guides/glossary/proof-roll/]
Propane / LP-gas: Liquefied petroleum gas, stored as a liquid under pressure and burned as a vapor
Property memory: The located, dated photo record that follows the building into operations, the as-built and equipment set the owner runs against
Proportional balancing: Setting outlets and branches as a ratio to the index (lowest-percent) outlet, then scaling the whole system with the fan [https://anvilfield.com/field-guides/glossary/proportional-balancing/]
Propylene glycol: The low-toxicity glycol (FDA generally recognized as safe) used in occupied-building HVAC; higher viscosity, slight heat-transfer penalty
Propylene glycol (PG): The common glycol in the secondary loop, often near 25 percent (PG25), for freeze protection and biostatic effect at a heat-transfer penalty
Prorated: Coverage whose payout declines as the roof ages, often after year 5 or 10
Protection mat: A non-woven geotextile separation layer between the membrane and the ballast that keeps stone from abrading the sheet
Protection pad / slip sheet: A compatible sheet between a support and the membrane that spreads load and separates materials
Protection period: The days the concrete is held warm and unfrozen until it reaches the strength to fend for itself
Protective relay testing: Secondary injection of current and voltage to verify the relay picks up and trips per the coordination study
Protective surfacing: The impact-attenuating material under and around equipment that cushions a fall; loose-fill or unitary
Protective system: Sloping, benching, shoring, or shielding used to protect workers from a cave-in
Protein residue: Nearly invisible film from a kitchen fire carrying the worst odor; emulsified off and heavily deodorized [https://anvilfield.com/field-guides/glossary/protein-residue/]
Proximity warning system: A detection system that senses when a person or object enters a zone around a machine and alerts the operator, the worker, or both. Also called a proximity detection system.
PRV: Pressure reducing valve, holds a set downstream pressure under the code ceiling [https://anvilfield.com/field-guides/glossary/prv/]
PRV (pressure reducing valve): A spring-and-diaphragm valve that holds the downstream pressure at a setpoint below the higher upstream pressure; also called a pressure regulator [https://anvilfield.com/field-guides/glossary/prv-pressure-reducing-valve/]
PSC motor: Permanent split capacitor; a fixed-speed blower whose airflow falls as static rises
PSD / NNSR / Title V: Major-source permitting tracks: deterioration review, nonattainment review, and operating permits
PSE: Power sourcing equipment, the switch or midspan that puts power on the line
PSE / PD: Power sourcing equipment (the switch or midspan) and the powered device at the far end
psi: Pounds per square inch of air pressure, kept low so the air does not crack pipe or heads
PSI / GPM: Pressure and flow, the two ratings that describe a jetter
psi / MPa: Pounds per square inch and megapascals; 1000 psi is about 6.9 MPa
psi / psig: Pounds per square inch; psig is gauge pressure above atmospheric, which is what the test gauge reads [https://anvilfield.com/field-guides/glossary/psi-psig/]
PSI vs GPM: PSI is the pressure that lifts the dirt; GPM is the flow that carries it away and sets the cleaning speed
psid: Pounds per square inch differential, the pressure difference the gauge reads across a check or the relief [https://anvilfield.com/field-guides/glossary/psid/]
psig / bar: System pressure at the gauge; about 14.5 psi equals one bar
psig / ounces: Pressure above atmospheric; heating steam often runs in ounces per square inch, 16 ounces to a psi [https://anvilfield.com/field-guides/glossary/psig-ounces/]
PSM: Process Safety Management, the OSHA program for covered processes, triggered for ammonia at 10,000 pounds.
Psychrometry / GPP: The science of the air-moisture relationship; GPP is grains of water vapor per pound of dry air [https://anvilfield.com/field-guides/glossary/psychrometry-gpp/]
PT ports: The pressure and temperature ports on a balancing valve, read with a DP gauge for flow and a probe for water temperature
PTAC: Packaged terminal air conditioner: self-contained through-wall unit with cooling and electric-strip heat
PTC / RTD: Embedded sensors that measure winding temperature directly, feeding a protection relay
PTHP: Packaged terminal heat pump: a PTAC that heats with a heat pump and falls back to electric strip
PTO: Permission to operate, the utility's authorization to energize and export
Public adjuster: A licensed professional who negotiates a claim for the homeowner; a contractor may not do this in most states
PUE: Power usage effectiveness, total facility energy divided by IT load energy, reported with its measurement level [https://anvilfield.com/field-guides/glossary/pue/]
PUE / WUE: Power usage effectiveness, a facility-efficiency ratio, and water usage effectiveness in liters per kilowatt-hour
Pugmill: The twin-shaft paddle mixer that blends a batch on a batch plant
Pull box: Enclosure where conductors are pulled, routed, or spliced between raceways, sized by 314.28 geometry
Pull planning: The trades planning backward from a milestone together, each owning its durations and handoffs, so the plan has buy-in
Pull planning / Last Planner: Trades build the sequence backward from a milestone so they own it
Pull-down: The slow, staged first cool-down of a new building to avoid thermal shock to the concrete and structure.
Pull-the-plug / black building test: The IST scenario where the utility is opened on purpose at load to simulate a real outage and prove ride-through
Pull-through: The repair, replacement, and upgrade revenue that flows from maintenance visits, measured as a ratio to agreement dollars held [https://anvilfield.com/field-guides/glossary/pull-through/]
Pulling tension (lbf): The force on the cable along the conduit, calculated to the puller and read live on the dynamometer
Pullout (withdrawal): The force needed to pull a fastener out of the deck, set by deck type and condition
Pullout / withdrawal: The force needed to pull a fastener out of the deck, measured by field pull test
Pump away: Piping the pump to pump away from the expansion tank so its differential pressure adds to the suction, raising NPSHa
Pump curve: The plot of pressure against flow for a fire pump, defined by the churn, 100 percent, and 150 percent points [https://anvilfield.com/field-guides/glossary/pump-curve/]
Pump curve / operating point: The manufacturer's flow-versus-head plot, and the point on it where your design flow meets your TDH
Pump-down: Closing the liquid line and running the compressor to store the charge on the high side
Pumping: Water and fines expelled from a saturated base under wheel load, hollowing voids under the pavement [https://anvilfield.com/field-guides/glossary/pumping/]
Pumping away: Placing the pump so it pushes water away from the expansion tank, adding its head to the loop instead of subtracting it
Pumping level / drawdown level: Where water falls to while the pump runs
Punch list: The list of incomplete, deficient, or damaged contract work at substantial completion, with a party and date per item [https://anvilfield.com/field-guides/glossary/punch-list/]
Punchout: A CRCP distress where the slab between two closely spaced cracks breaks loose
Purchase order (PO): A document authorizing a buy against a job, naming the items, the agreed price, and a tracking number
Purge: A sector on a wheel that flushes carried-over exhaust before the matrix rotates into the supply stream
Purlin / girt (secondary): Cold-formed Z or C members that span between frames to carry the roof (purlins) and wall (girts) panels and brace the frames
Purple pipe: The purple-colored or purple-marked piping that identifies non-potable reclaimed, rain, or graywater
Purple pipe / Pantone 512: The reclaimed identification color, carried in pipe, tape, tags, and boxes with a do-not-drink warning
Push (resistance) pier: A steel pier driven by hydraulic ram using the building's weight as reaction, for settlement repair and lift
Push-pull: A fast recovery method for large liquid charges that drives liquid into the cylinder using machine-generated pressure
Put-up: The manufacturer's stated length of conductor on the reel, shown on the tag
PVB: Pressure vacuum breaker; one check and an air inlet, back-siphonage only, holds continuous pressure, testable (ASSE 1020) [https://anvilfield.com/field-guides/glossary/pvb/]
PVB / AVB: Pressure or atmospheric vacuum breaker; protects against back-siphonage only, not backpressure
PVB / SVB: Pressure vacuum breaker and its spill-resistant version, a check plus an air inlet for backsiphonage only (ASSE 1020 / 1056)
PVC: Polyvinyl chloride, a heat-weldable thermoplastic membrane, the chemical and grease resistance leader
PVC (Schedule 40/80): Rigid nonmetallic conduit; Schedule 80 has thicker walls for physical damage
PVDF / Kynar: A fluoropolymer paint finish that holds color and resists chalk for decades
PVDF / Kynar vs SMP: PVDF is the premium fluoropolymer paint; SMP is the cheaper, faster-fading polyester finish
PVHCS / UL 3741: PV hazard control system, an array-level listed alternative for the inside-boundary protection [https://anvilfield.com/field-guides/glossary/pvhcs-ul-3741/]
PVRSE: PV rapid shutdown equipment, a component listed on its own under UL 1741
PVRSS: PV rapid shutdown system, the inverter and rapid-shutdown components listed together under UL 1741
PWL: Percent within limits, the share of a lot estimated to fall inside the specification limits, used for statistical acceptance and pay [https://anvilfield.com/field-guides/glossary/pwl/]
PWM: Pulse width modulation, the switched-pulse output that averages to the AC waveform the motor uses
Pylon / monument foundation: The engineered footing for a freestanding sign, commonly a reinforced drilled pier with cast-in anchor bolts
Pz: Zone population, the number of people in the zone during use
Q: Cooling load in tons of refrigeration the tank has to carry during the ride-through
q-allow: Allowable soil bearing pressure in psf, from the geotechnical report, with safety factor included
Q_loss: Loop heat loss in BTU per hour, from the pipe size, length, and insulation
QC / QA: Quality control is the contractor's process testing; quality assurance is the owner's independent verification and acceptance
QD: Quick-disconnect, a dripless coupling that joins a node to the manifold for live service [https://anvilfield.com/field-guides/glossary/qd/]
QD / taper-lock bushing: A split tapered bushing that clamps a sheave to the shaft with bolts and a key
QOD: Quick-opening device, an accelerator or exhauster that speeds the trip and the air clearing on a larger system
Qualified person: A person trained in the construction and operation of the electrical equipment and its hazards, who establishes and verifies the safe work condition
Quality assurance (QA): The planning, procedures, roles, and standards that make quality happen, set before the work starts [https://anvilfield.com/field-guides/glossary/quality-assurance-qa/]
Quality control (QC): The inspection, testing, and measuring of the actual work against the acceptance criteria as it is built [https://anvilfield.com/field-guides/glossary/quality-control-qc/]
Quick-closing valve: A valve that shuts fast, such as a solenoid, washer or dishwasher fill, or flushometer, that creates the surge
Quick-disconnect (QD): A dripless blind-mate coupling joining a server to the manifold for live service, the number one leak point [https://anvilfield.com/field-guides/glossary/quick-disconnect-qd/]
Quick-disconnect (UQD / UQDB): A dripless coupling, blind-mate in the UQDB form, that lets a part come off the loop without spilling or draining
Quote-to-close time: How long a proposal sits before it sells; shorter means less lost to delay and ghosting
R: Conductor resistance in ohms per 1000 ft, from NEC Chapter 9, Table 8 or Table 9
R / P suffix: R is the receptacle (the slots in the wall), P is the plug (the blades on the cord)
R-value: Thermal resistance of the insulation; figured on a taper as both an average and a thinnest-point minimum
R-value (installed): Thermal resistance of the insulation at its installed, uncrushed thickness, the value the code checks
R-value / R per inch: Thermal resistance of the assembly, and the resistance of a single inch of a given board
R-value vs air leakage: R-value is resistance to conductive heat flow; air leakage is bulk air through gaps, carrying both heat and moisture
Ra: Outdoor air rate required per unit area, in cfm per square foot
Raceway: An enclosed channel made to hold conductors, such as conduit or tubing
Raceway / raceback: The aluminum box or backing behind channel letters that holds the wiring and supplies and consolidates penetrations
Rack and pinion: The toothed rack on the mast and the powered pinion gear that meshes with it to drive the platform up and down
Rack BBU: Battery backup unit: a lithium battery in the rack or a sidecar shelf that carries the load through a blip and bridges to the generator
Rack cooling index (RCI): How well rack intake temperatures stay inside the ASHRAE recommended range, at the hot and cold ends
Rack inlet temperature: The air temperature entering the equipment, judged against the ASHRAE TC 9.9 allowable envelope through the ride-through [https://anvilfield.com/field-guides/glossary/rack-inlet-temperature/]
Rack PDU: The power distribution strip in the cabinet, in basic, metered, or switched grades, commonly 0U in the rear channel [https://anvilfield.com/field-guides/glossary/rack-pdu/]
Rack U: Rack unit, 1.75 in of vertical mounting space, the unit assets and rack space are measured in
Rack-and-stack: The physical install of servers, storage, and network gear into racks after the facility is ready, plus the migrations that load workloads in
Racking: Flexing a panel so it follows a slope while the pickets stay plumb, versus stepping it level
Racking / mounting: The structural hardware that holds the PV array on the roof and carries its load into the structure
Radius: The horizontal distance from the crane's center of rotation to the load; rated capacity drops as the radius grows
Radius of action: The distance from the vibrator head over which it actually consolidates concrete
Radon: A radioactive gas from the natural decay of uranium in soil and rock, a leading cause of lung cancer indoors
Rain load: The structural load from ponded water plus hydraulic head, per ASCE 7, about 5.2 lb/sq ft per inch [https://anvilfield.com/field-guides/glossary/rain-load/]
Rainfall intensity: Design rain rate in inches per hour for a return period, from the code map or NOAA
Rainscreen: A drained, vented gap behind the siding, made with furring, that lets the wall drain and dry
Raised access floor: A grid of removable panels on adjustable pedestals above the structural slab, with the void below used as a plenum
Raised floor / slab: Access floor on pedestals with a plenum, versus racks on the structural slab
Random vs defined traffic: Random traffic moves any direction and uses FF/FL; defined traffic follows a fixed wheel path and uses F-min or waviness
Range: Hot water temperature entering the tower minus cold water temperature leaving it [https://anvilfield.com/field-guides/glossary/range/]
RAP: Reclaimed asphalt pavement, the milled or crushed existing asphalt reused as aggregate and a binder source [https://anvilfield.com/field-guides/glossary/rap/]
RAP / RAS: Reclaimed asphalt pavement and reclaimed asphalt shingles, recycled binder and aggregate reused in the mix [https://anvilfield.com/field-guides/glossary/rap-ras/]
Rapid shutdown: NEC 690.12 function that collapses voltage on the building conductors for responder safety, which does not de-energize the array in the field [https://anvilfield.com/field-guides/glossary/rapid-shutdown/]
RAPL / BMC: Running Average Power Limit, the CPU power-cap feature, and the baseboard management controller that enforces caps out of band
Rate of placement (R): The vertical rise of fresh concrete in the form per hour, a main driver of form pressure
Rate of rise: How fast the micron reading climbs after isolating the pump; its speed and shape separate a leak from moisture
Rated (1 to 4): ANSI/TIA-942 level, a separate prescriptive system covering four domains, not interchangeable with Tier
Rated capacity: The maximum platform load, people plus tools plus material, that the machine is rated to carry, de-rated by reach
Rated capacity / load chart: The weight the deck can carry and how it must be distributed, posted for the specific machine and configuration
Rated fire media: Fire glass or lava rock made for fire features; regular stone traps moisture and can explode
Rated point (100 percent): The design condition, the rated flow at rated pressure the system was sized around
Rating (2A:10B:C): The classes an extinguisher covers and its tested capacity on Class A and B fires
Raveling: Loose aggregate shedding from the surface, the leading pervious failure, from bad paste, low compaction, or poor curing [https://anvilfield.com/field-guides/glossary/raveling/]
Raveling / weathering: Surface loss of aggregate and graying as the binder oxidizes and hardens; a surface, not a base, problem
RBC / UBC: Rack bonding conductor to the grid and unit bonding conductor from equipment to the rack busbar
RCC: Roller-compacted concrete, a zero-slump concrete placed by paver and compacted with rollers
RCI: Rack Cooling Index; how well inlet temperatures sit inside the ASHRAE envelope, 100 percent is clean [https://anvilfield.com/field-guides/glossary/rci/]
RCL: Refrigerant concentration limit per ASHRAE 15, the most refrigerant allowed in the smallest occupied room if it leaks
RCM: Reliability-centered maintenance; sets each asset's strategy by criticality, function, and failure modes
RCR: Room cavity ratio, a shape factor for the room that selects the CU from the table
RCSC: The Research Council on Structural Connections specification for high-strength bolted joints, including the snug-tight and pretensioned methods
RDHx: Rear-door heat exchanger, a water coil replacing a rack's rear door that captures the server exhaust heat at the rack
RDMA / NVMe-oF: Remote direct memory access and NVMe over Fabrics, the network protocols that let remote flash feed GPUs at near-local speed
RDMA / RoCE / InfiniBand: Remote direct memory access for GPU fabrics, carried over Ethernet (RoCE) or InfiniBand
RDS: Refrigerant detection system, the sensor that triggers A2L leak mitigation
Re-commissioning (ReCx): Commissioning again a building that was commissioned before and has drifted
Re-enterable device: A firestop pathway sleeve or box with a self-sealing intumescent insert that holds the rating as cable is added or removed
Re-entrant corner: An inside corner where stress concentrates and a crack tends to run out at about 45 degrees [https://anvilfield.com/field-guides/glossary/re-entrant-corner/]
Re-identification: Permanently re-marking a conductor to read as a different type where allowed
Reactance: AC opposition from the conductor's magnetic field, significant on large or long runs
Reactivation: Marketing back to past customers to win repeat work; the cheapest revenue most trade businesses have
Reactivation / regeneration air: The heated airstream that strips moisture off the desiccant and exhausts it
Reactive / preventive / predictive: Run-to-failure; scheduled on a calendar or runtime; condition-based, triggered by measured condition
Reactive maintenance: Run-to-failure repair after the equipment breaks; the exception on critical gear, never the plan
Reactivity coupon: A copper or silver strip exposed in the space; its corrosion thickness sets the severity level
Reactivity monitoring: Exposing copper and silver coupons for a set period and reading the corrosion to classify the environment
Ready-mix concrete: Concrete batched at a plant to a set recipe and delivered by truck ready to place
Reality capture: Recording real-world conditions as measurable 3D data, the truth source you design and verify against
Rear-door heat exchanger: An air-to-liquid coil that replaces the rack's back door and cools the exhaust at the rack
Rebar #4: Reinforcing bar 1/2 in across, the minimum rebar size for a concrete-encased electrode
Rebar cage: The cylinder of longitudinal bars and spiral reinforcement that gives the shaft tension, shear, and bending capacity
Rebar cage / bond beam: The cage is the tied grid of reinforcing bar that gives the shell its tensile strength; the bond beam is the thickened, extra-reinforced top perimeter that carries the tile, coping, and deck edge and ties the walls together.
Rebound: Aggregate-rich material that bounces off and must not be reincorporated; rises overhead and on dry-mix
REC / PPA: Renewable energy certificate (an attribute) and power purchase agreement (a contract for specific output)
Recap: The summary that rolls labor, material, DJE, and quotes into job cost, then adds overhead and profit
Receiver: The air storage tank that buffers demand and smooths pressure; an ASME pressure vessel
Receptacle / outlet: The device a plug connects to; outlet is the broader code term for any point current is taken
Receptor: The open fixture that catches the indirect waste, usually a floor sink, with its own trap and vent
Recirculation: Hot exhaust air pulled back into the equipment inlets, raising inlet temperature above supply [https://anvilfield.com/field-guides/glossary/recirculation/]
Recirculation loop: The supply-and-return circuit that keeps hot water moving so it is hot at the far fixture [https://anvilfield.com/field-guides/glossary/recirculation-loop/]
Reclaimed / recycled water: Municipally treated wastewater delivered as a separate non-potable supply for approved uses
Recoat: Cleaning and re-coating the roof on a roughly 10 to 15 year cycle to renew the protection
Recombinant: The VRLA design that recombines about 95 to 99 percent of the gas back to water on normal charge
Recommended range: The conservative steady-state band, about 18 to 27 C (64 to 81 F) for all classes
Record drawing: The designer's official set, produced from the as-builts by screening and incorporating the changes; carries the design professional's review
Recordable: A work-related injury or illness meeting the 300 log criteria, such as treatment beyond first aid or days away
Recordable vs reportable: Recordable goes on the 300 log; reportable means the call to OSHA for a fatality or severe injury
Recover (overlay): A new roof covering installed over the existing roof without removing it
Recover board: A dense board over the insulation or old roof that gives the membrane a hard base
Recover vs restoration: A recover lays a new membrane over the old as a roof layer; a restoration coats the existing roof and usually does not count as a new layer
Recover vs tear-off: A new membrane over the old one (recover) versus stripping to the deck (tear-off); moisture and code layers decide
Recoverable depreciation: Depreciation held back on the first check and released after the work is completed and documented
Recovered binder: The aged asphalt binder still coating the RAP aggregate, recovered or accounted for in the mix design
Recovery: The fraction of RO feed water that becomes permeate rather than going to reject [https://anvilfield.com/field-guides/glossary/recovery/]
Recovery rate (GPH): Gallons per hour the heater raises across the cold-inlet temperature rise
Recurring revenue: Revenue you can predict because it repeats on a schedule, from renewing agreements, rather than from one-off transactions [https://anvilfield.com/field-guides/glossary/recurring-revenue/]
Red tag / correction notice: A failed inspection and the list of items to fix before a re-inspection
Red-line: The mark made directly on the drawing, in red, to show a field change as it happens, with the date and reason
Reducer: A change in pipe diameter, confirmed by the size callout on each side of the fitting
Reduction cut: Shortening a limb back to a living lateral at least about a third the stem diameter, the alternative to topping
Referral rate: The share of new customers sent by past customers; the cheapest lead source a trade business has
Reflectance / ORL: Light reflected by one event, and total reflected by the link; more negative is better
Reflected apparent temperature: The temperature of the surroundings that reflects off the target and into the camera, which corrupts the reading on low-emissivity metal
Reflected ceiling plan (RCP): The plan view of the ceiling looking up, showing the grid, borders, and every light, diffuser, and device
Reflected wave: Voltage doubling at the motor terminals from impedance mismatch on a long cable run
Reflective cracking: A base-slab crack or joint telegraphing up through the overlay in the same pattern [https://anvilfield.com/field-guides/glossary/reflective-cracking/]
Reflective cracking / interlayer: The old crack reappearing through the overlay, and the stress-relief layer (SAMI, fabric, geogrid) that slows it
Refrigerant stacking: Refrigerant pooling in the condenser at high load and very low condenser-water temperature, costing capacity
Refrigeration rack: Parallel compressors on shared piping feeding a store, split into medium-temp and low-temp suction groups, with staged capacity and redundancy
Refusal: When a pier stops advancing before design depth against rock, cobbles, or fill; resolved by relocating, advancing past, or load testing, not forcing.
Refusal and set: The point where the pile stops advancing under the hammer, and the penetration per blow
Regeneration / reactivation: Heating the loaded desiccant to drive the held moisture back off into an exhaust airstream
Registered apprenticeship: A program approved by the DOL or a state agency to standards at 29 CFR Part 29, earning a recognized credential
Registration: Stitching individual scans into one aligned cloud, target-based or cloud-to-cloud, reported with a registration error [https://anvilfield.com/field-guides/glossary/registration/]
Reglet: A saw-cut groove in masonry that holds a counterflashing, sealed to keep water out of the cut [https://anvilfield.com/field-guides/glossary/reglet/]
Regular rate: The pay rate the overtime multiplier applies to, which can include more than the base hourly wage
Regulated medical waste: Contaminated material handled under medical-waste rules: red-bagged or in sharps containers, manifested, and sent to licensed disposal
Regulated waste: Asbestos debris that must be wetted, double-bagged, labeled, manifested, and disposed of at a permitted facility
Rehabilitation / reconstruction: Restoring structure and ride to failed-down pavement, versus rebuilding failed pavement from the subgrade up; neither is preservation
Reheat: Adding heat to dehumidified air to raise its supply temperature, ideally from recovered heat rather than new energy
Reheat dead band: The temperature range where the box holds minimum airflow with the reheat valve shut
REI: Restricted-entry interval, the label time after application before re-entry without the required PPE
Reimbursable: A job cost billed back to the customer, usually with a contract markup, as opposed to overhead the company absorbs
Reinforced zone: The compacted, grid-bound block of soil behind the face that acts with the wall as a mechanically stabilized earth mass
Reinforcement fabric: Polyester fabric embedded in the coating at seams, laps, and fastener rows for tensile strength and crack-bridging [https://anvilfield.com/field-guides/glossary/reinforcement-fabric/]
Reinforcing mesh: Alkali-resistant fiberglass embedded in the EIFS base coat for impact and crack resistance
Rejuvenator: A product that penetrates and restores aged asphalt binder by replacing lost maltenes, softening it and bringing back flexibility [https://anvilfield.com/field-guides/glossary/rejuvenator/]
Rejuvenator / recycling agent: An oil or additive that restores lighter fractions to aged binder, softening it back toward fresh behavior
Related instruction (RTI): The classroom or online theory, code, and safety, commonly about 144 hours per year in a registered program
Relative compaction: In-place dry density as a percentage of the Proctor maximum dry density
Relative humidity: The water vapor present compared to the maximum at that temperature, in percent; a ratio, not a quantity
Relative humidity (RH): Air moisture in percent; lower RH raises resistance, so it is recorded with every reading [https://anvilfield.com/field-guides/glossary/relative-humidity-rh/]
Relative humidity vs dew point: RH is how full the air is as a percent; dew point is the temperature at which water condenses, and it sets which surfaces sweat
Release agent: A bond breaker that keeps the stamp from sticking; pigmented powder versions also leave a secondary accent color
Release agent (form oil): The film applied to the form face so it strips clean without bonding to or staining the concrete
Release detection / ATG: Required monitoring that finds a UST leak early; an automatic tank gauge is one in-tank method, interstitial monitoring is the method for new secondarily contained systems
Release rate: The maximum the site may discharge, set by the stormwater authority, often in cfs per acre
Relief air: The planned path that lets a positive building bleed its surplus out, gravity or powered
Relief valve opening point: The differential at which an RP's relief valve starts to discharge the zone, commonly 2.0 psid or greater
Relief vent: A second air path on a circuit-vented branch with four or more closets tying into a stack loaded from above
Remainder / balance: The conductor left on a reel after one or more pulls
Remaining service life: The estimated number of years a roof has left before it needs replacement
Remote hands / smart hands: Provider technicians doing physical work (remote) or technical work (smart) in your space when you are not on site
Remote-hands: A local or dispatched technician who does the physical task the remote team cannot, under guidance
Renewal rate / churn: The share of expiring agreements that renew, and its mirror, the share that leave; two views of whether the base holds
Renovate Right: EPA's lead-hazard pamphlet that the firm must deliver to owner and occupants before a covered renovation
Rent commencement: The lease date the tenant starts paying rent, which the fit-out schedule is built to meet
Repair behind the bar: Removing the chloride-contaminated concrete behind a corroded bar, about 3/4 in clearance, so the full circumference is cleaned
Repair, restore, replace: The three actions: fix a local defect, coat or recover a worn but sound roof, or tear off and rebuild
Repeat rate: The share of work that comes from customers you have served before; a direct measure of whether follow-up is working
Repellent: A scent or taste product that makes a plant unpleasant, reducing browse but not eliminating it, and subject to wash-off and habituation
Replace vs restore: The adjuster's item-by-item call: restore when it costs less than replacement, replace when it does not
Repointing: Removing deteriorated outer mortar from joints and replacing it with fresh, compatible mortar
Reportable: An event that triggers direct notification to OSHA on a clock: fatality, in-patient hospitalization, amputation, or eye loss
Reported problem: What the caller said was wrong, in their words, before diagnosis
Reporting boundary: The defined line around what counts as facility, IT, and another party's responsibility
Reporting time pay: Show-up pay, the minimum some states or CBAs require when you report and the work is not there
Rescue plan: The site-specific plan to bring a stranded or fallen worker down under control before suspension trauma sets in
Reserve alkalinity: A titration that measures the buffer left in the fluid; falling against baseline means the inhibitor is depleting
Reserve area: Suitable soil set aside and protected for the future replacement field, required by many codes
Reservoir void ratio: The share of the open-graded stone layer that is open space, commonly near 40 percent, where the water stores
Residual pressure: The flowing pressure left at a fixture while water is running, what proves the far fixture is served [https://anvilfield.com/field-guides/glossary/residual-pressure/]
Residual rate: The amount of actual asphalt left after the water or solvent leaves, the number specifications set for tack [https://anvilfield.com/field-guides/glossary/residual-rate/]
Residual sensing: Summing CTs on all three phases and the neutral, where the net should be zero
Residual strength: The load a fiber concrete carries across a crack after cracking, measured by ASTM C1609 or C1399
Residual value: The resale or salvage value expected at the end of the machine's working life
Resilient flooring: Hard, wipeable floor covering: LVT, LVP, VCT, sheet vinyl, rubber, and linoleum
Resilient modulus (Mr): The stiffness of the subgrade under repeated wheel loading, the main subgrade input to AASHTO design
Resistive vs reactive bank: Resistive loads at unity PF (engine only); reactive adds kVAR to test the alternator and AVR at rated current
Resistivity: Water's resistance to current, in megohm-cm at 25°C; higher is purer, ~18.2 is ultrapure
Respirable crystalline silica: The fraction of silica dust fine enough to reach deep into the lungs, released by cutting, grinding, drilling, or breaking concrete, masonry, stone, or brick [https://anvilfield.com/field-guides/glossary/respirable-crystalline-silica/]
Restoration: Re-grinding and re-polishing an existing terrazzo floor back to a new finish, the reason terrazzo lasts for generations
Restoration coating: A fluid-applied membrane coated over an existing sound roof to renew it and extend its life without a tear-off
Restrained joint: A pipe joint that carries tension, locking the pipe so it resists pullout
Restrained length: The length of pipe each side of a fitting that must be restrained so soil friction holds the thrust
Restraint: Anything that stops concrete moving freely as it shrinks or contracts, turning movement into tension
Retail vs wholesale colo: Retail sells by the cabinet or cage in shared halls; wholesale sells suites or data halls, usually 100 kW and up, with more tenant control
Retainage: A percentage, often 5 to 10 percent, held back from progress payments until project closeout [https://anvilfield.com/field-guides/glossary/retainage/]
Retainage / retention: The percentage of payment withheld until completion, commonly reduced at substantial completion and released at final; set by contract and statute [https://anvilfield.com/field-guides/glossary/retainage-retention/]
Retainage receivable / payable: Retainage held from you is an asset (receivable); retainage you hold from subs is a liability (payable); ask a CPA about classification and timing.
Retempering: A one-time, recorded jobsite water addition allowed under ASTM C94 within the design w/c limit
Retention: How many days of footage the system keeps, commonly 30, 60, or 90; usually set by spec, insurer, or local rule, and it multiplies the storage [https://anvilfield.com/field-guides/glossary/retention/]
Retention / churn: Keeping trained staff versus the rate at which they leave; churn costs the person, the knowledge, and the training investment
Retention / hold time: The minimum time the room must hold the agent at the protected height, commonly at least 10 minutes under NFPA 2001
Retention bond: A surety bond posted in lieu of cash retainage so the held money is freed while the owner keeps equivalent security; availability varies by contract and state.
Retention time: The minutes wastewater stays in the tank, the basis of gravity interceptor sizing
Retro-commissioning: Tuning existing equipment and controls back to proper operation; an audit finds the waste, retro-commissioning corrects the operational part.
Retro-commissioning (RCx): The first commissioning of an existing building that was never commissioned
Retroreflectivity: Light from a headlight returned toward the driver by glass beads, measured in mcd/m2/lux at 30-meter geometry [https://anvilfield.com/field-guides/glossary/retroreflectivity/]
Return loss: Signal reflected by an impedance change; a kink or an over-cinched tie throws it
Return static: Negative pressure read after the filter and before the blower
Return temperature: The temperature of the water coming back to the heater, held above the growth-band floor
Return temperature index (RTI): Unit delta-T divided by IT delta-T, as a percent; below 100 is bypass, above 100 is recirculation
Reveal: The deliberate, consistent gap around a door, drawer, or panel; the consistency is the quality tell
Revenue grade: Metering accurate enough to bill against, commonly ANSI C12.20 Class 0.2 or 0.5
Revenue-grade: Meter accurate enough to bill against, meeting ANSI C12.20, typically Class 0.2 or 0.5
Reverse power (32): Protection that trips a set being motored, when real power flows into it instead of out
Reversing valve: Four-way valve that reverses refrigerant flow to switch a heat pump between heating, cooling, and defrost [https://anvilfield.com/field-guides/glossary/reversing-valve/]
Reversing valve (O/B): The heat-pump valve that switches between heating and cooling, driven by the O or B terminal
Review velocity / recency: How steadily and how recently new reviews arrive; a steady weekly flow ranks better than a large pile of old reviews
Revise and resubmit: A review stamp returning a submittal for correction, which restarts the review clock
REX (request-to-exit): A button or sensor that tells the controller a legitimate exit is happening so it does not alarm; it is not the means of egress
RF exposure zone: Controlled (occupational) and uncontrolled (general-public) areas with different FCC maximum permissible exposure limits
RFI: Request for information, the formal question whose answer often moves the work; its number ties to the resulting red-line [https://anvilfield.com/field-guides/glossary/rfi/]
RFID vs BLE vs UWB vs GPS: Location technologies ordered by precision and cost: RFID is cheap read-or-no-read, BLE is zone level, UWB is sub-meter, GPS is outdoor
RGA / RMA: Return goods or materials authorization; the number that allows the defective part to be returned
RH: In-slab relative humidity as a percentage, read by an in-situ probe at depth (ASTM F2170)
RH (ASTM F2170): Relative humidity inside the slab, read by in-situ probe as a percentage [https://anvilfield.com/field-guides/glossary/rh-astm-f2170/]
RH (relative humidity): The moisture in the slab as a percentage, read by an in-situ probe at depth under ASTM F2170
Rhizome / stolon: Spreading stems, below ground (rhizome) or above (stolon), that let a grass fill in and self-repair
RHO: Thermal resistivity of the soil or backfill in degrees C-cm per watt; lower RHO carries heat away and raises ampacity
RICE NESHAP: 40 CFR Part 63 Subpart ZZZZ, hazardous-air-pollutant standards for reciprocating engines
Ride-through: The window between a power or cooling loss and full recovery, during which the critical load and room temperature must hold [https://anvilfield.com/field-guides/glossary/ride-through/]
Ride-through / hold-up: The short window the BBU carries the load, sized to the generator start, not to long runtime
Ridge-to-valley depth (RVD): The height of the milled texture, from a ridge top to a valley bottom
Riding the curve: How the operating point slides along the pump curve when a valve throttles or the system resistance changes
Right plant, right place: Selecting a plant whose sun, soil, water, and mature-size needs match the conditions of its spot so it thrives with little input
Rigid / PCC pavement: A portland cement concrete slab that carries load by beam action, as opposed to flexible asphalt [https://anvilfield.com/field-guides/glossary/rigid-pcc-pavement/]
Rigid frame / primary framing: The built-up tapered columns and rafters that form the main moment-resisting structure and carry the load to the anchor bolts
Rigid pavement: Concrete pavement, a stiff slab that bridges and distributes load by beam action
Riser: A vertical supply pipe carrying water up to the floors and branches [https://anvilfield.com/field-guides/glossary/riser/]
Riser (CMR/CL2R/FPLR): The cable rating for vertical runs between floors; passes a floor-to-floor flame test
Riser clamp: A clamp whose ears bear on the floor structure to support a vertical pipe at each floor
Riser diagram: A flat schematic of the vertical stacks and risers floor to floor, often single-line
Risk rating: The matrix output, low, moderate, high, or extreme, that drives the monitor, mitigate, or remove decision
Risk register: The list of identified risks behind the contingency, each scored by likelihood and impact, used to size and then draw down the contingency.
RMC / IMC / EMT: Rigid metal conduit, intermediate metal conduit, electrical metallic tubing
RO / permeate / reject: Reverse osmosis; the purified water through the membrane is permeate, the concentrated leftover is reject or concentrate
Robotic total station: A one-person instrument that measures angle and distance to a tracked prism, accurate to a few millimeters, for building layout
RoCE: RDMA over Converged Ethernet, running RDMA on Ethernet made lossless with PFC and ECN, versus InfiniBand's credit-based lossless fabric
Rodding / jetting: Clearing a drain with a powered cable, or with a high-pressure water hose
Roll to seat: Rolling porous asphalt only enough to lock the mat, not to chase density, so the surface voids stay open
Roller / glide support: A support that lets pipe slide as it expands and contracts, so it does not abrade the roof or stress fittings
Roller tube screed: A spinning tube pulled across the surface; handles slopes, less operator-dependent
Rolling load: Dynamic load from a wheel rolled across the panel for a set number of passes, the data-hall case that usually governs [https://anvilfield.com/field-guides/glossary/rolling-load/]
Rolling pattern: The fixed pass count, overlap, speed, and gap each roller runs, set on a test strip and held to keep density uniform
Rolling sphere: A design sphere, commonly 150 ft radius, rolled over the structure to find exposed points needing terminals
Roof asset management: Treating each roof as a tracked capital asset: inventory, condition rating, remaining-life estimate, and a multi-year capital plan
Roof condition index: A score, commonly 0 to 100, that puts every roof on one consistent scale for comparison and ranking
Roof condition rating: A consistent score of a roof's overall condition used to estimate remaining life and plan capital
Roof curb: The steel frame that carries the unit, routes the duct through the roof, and seals it watertight
Roof expansion joint: The watertight roof detail over a structural expansion joint, built on two raised curbs with a flexible cover spanning the gap to take the building's movement
Roof hatch / scuttle: Hinged insulated cover on a curb that frames the opening through the roof
Roof moisture survey: An infrared scan, usually after sunset, that locates wet insulation by the heat it retains, per ASTM C1153.
Roof snow load: The design snow weight on the roof, derived from the ASCE 7 ground snow load and its factors, in psf
Roof tarping (dry-in): Temporary weatherproofing of a damaged roof with poly sheeting, run and anchored so water sheds off the building
Roofing square: 100 square feet of roof area, the unit of measure and pricing
Rooftop avalanche: The sudden release of a whole snowpack off a slick or steep roof, the hazard retention is built to prevent
Room integrity / door fan test: A pressurization test that measures enclosure leakage to confirm a clean agent room holds concentration for the required time
Room pressure monitor: A permanently installed instrument that continuously shows the pressure direction at the door and alarms when it is lost
Root ball: The mass of soil and roots dug with the tree, sized by trunk caliper per ANSI Z60.1
Root barrier: A layer, or a certified root-resistant membrane, that keeps roots from penetrating the waterproofing
Root cause: The actual underlying reason a callback happened, usually a crew, a detail, or a product, as opposed to the symptom you fixed on the visit. Fixing it removes future callbacks instead of just covering them. [https://anvilfield.com/field-guides/glossary/root-cause/]
Root cause analysis (RCA): The structured search after restore for the real cause and contributing factors, not the first symptom, often using the 5-whys
Root flare: The point where the trunk widens into the first main roots, which must sit at the surface and stay exposed [https://anvilfield.com/field-guides/glossary/root-flare/]
Root flare / trunk flare: Where the trunk widens into the first main roots; it must sit at or just above finish grade
Root pruning: Cutting a ring of roots months to a year ahead so fibrous roots regrow inside the future ball line
Root zone: The depth of soil the plant's active roots occupy, which a cycle should wet and then let dry
Root-cause code: The reason a callback happened: workmanship, bad part, misdiagnosis, or rushed
Rootzone: The engineered soil or sand layer the turf roots into, built to drain and resist compaction [https://anvilfield.com/field-guides/glossary/rootzone/]
Rope / cable sensor: A continuous linear element that senses fluid anywhere along its length and reports the location, for distributed coverage
Rotation / changeout: A scheduled replacement of the color display, pulling the spent planting and installing the next season's flowers
Rough-in: The drain, vent, and supply piping set to a fixture in the open wall and floor, tested and inspected before the surfaces close [https://anvilfield.com/field-guides/glossary/rough-in/]
Rough-in sheet / cut sheet: The manufacturer's dimensioned drawing for a fixture, giving drain, supply, and clearance dimensions from the finished surfaces
Rough-in test: The test of the bare piping before fixtures and before close-in, proving the joints hold
Route and seal: Widening a non-structural crack into a groove and filling it with a flexible sealant
Rp: Outdoor air rate required per person, in cfm per person, from the 62.1 occupancy table
RP / RPZ: Reduced pressure principle assembly; two checks plus a relief valve, for high hazard and both flow directions [https://anvilfield.com/field-guides/glossary/rp-rpz/]
RP / RPZ / RPBA: Reduced pressure zone assembly; two checks plus a relief valve, for high hazard and both backflow mechanisms (ASSE 1013)
RP assembly: Reduced-pressure principle backflow assembly protecting the potable makeup connection
RPO: Recovery point objective, the maximum tolerable data loss, measured in time back to the last good copy
RPP: Remote power panel, a panelboard fed from the PDU and placed near the rows to shorten branch runs [https://anvilfield.com/field-guides/glossary/rpp/]
RPZ / RP: Reduced pressure principle assembly, the highest-protection testable backflow assembly (ASSE 1013)
RPZ backflow preventer: A reduced-pressure-zone assembly that stops sump water from siphoning into the potable supply
RRP Rule: EPA's Renovation, Repair, and Painting Rule (40 CFR 745, Subpart E) for work that disturbs lead paint in pre-1978 homes and child-occupied facilities
RRP vs abatement: RRP is renovation that controls lead dust along the way; abatement is work whose purpose is to permanently remove lead, under separate stricter rules
RRU / antenna: Remote radio unit, the transceiver mounted at the antenna, and the antenna panel that radiates each sector
RTE: Round-trip efficiency, energy out on discharge divided by energy in on charge
Rtg / Rg: Resistance-to-ground, measured from one floor electrode to the bonded ground point
RTI: Return Temperature Index; above 100 percent is recirculation, below 100 percent is bypass [https://anvilfield.com/field-guides/glossary/rti/]
RTI = 100%: Unit delta-T matches IT delta-T; the supply air does its work and returns fully heated
RTI above 100%: Recirculation; rack airflow exceeds cooling airflow and exhaust is pulled back to the inlets
RTI below 100%: Bypass air; cooling airflow exceeds rack airflow and cold supply short-circuits to the return
RTLS: Real-time location system, tracking the position of tagged assets or people against fixed reference points
RTO: Recovery time objective, the maximum tolerable downtime before a system must be restored
Rtt / Rp: Point-to-point resistance, measured between two electrodes on the floor surface
RTT / RTG: Resistance point-to-point and resistance-to-ground, the ESD floor measurements per ANSI/ESD STM7.1
RTU / AHU / FCU: Rooftop unit, air handling unit, and fan coil unit, the common air-side equipment names
RTU / AHU / VAV / VRF: Rooftop unit, air handler, variable-air-volume box, and variable refrigerant flow
RTU / packaged unit: A self-contained HVAC unit with cooling, heating, fans, and often an economizer in one cabinet on a roof curb
RU / U: Rack unit, 1.75 in of vertical mounting height; an open U is a recirculation path without a blanking panel [https://anvilfield.com/field-guides/glossary/ru-u/]
Rule of 20 percent: Acclimatization ramp: about 20 percent of normal workload day one, adding roughly 20 percent each day
Rule-based vs data-driven: Rules encode physics or sequence logic and are transparent; data-driven methods learn normal patterns and flag anomalies
Runbook: The step-by-step migration plan with owners, order, dependencies, downtime, and a defined rollback
Running bond: The brickwork-style staggered joint pattern that keeps sod seams from lining up
Running slope: The slope down the ramp run in the direction of travel, held to 8.3 percent (1:12) maximum
Running vs stack bond: Half-block offset that interlocks the wall, versus aligned head joints that need added horizontal steel
Runoff coefficient: The fraction of rainfall a catchment surface actually sheds to collection, around 0.9 for clean metal
Rupture basin: An open-top containment under the day tank sized to hold the full tank volume, with a leak alarm
Rust converter: A phosphoric-acid product that turns flaky iron oxide into a stable iron phosphate the primer can bond to
Rust-inhibitive primer: A primer, often zinc-phosphate based, that binds remaining rust and blocks moisture before the coating
Rut box: A spreader box with V-shaped screeds that fills wheelpath ruts with micro-surfacing before a surface course
Rutting: A wheelpath depression from deformation or consolidation in the asphalt, base, or subgrade
RV: Relief valve, the part on an RP that dumps the zone to atmosphere when a check fails
RVS / RVSS: Reduced-voltage starting, and the solid-state soft starter version of it
RWL: Recommended weight limit, the NIOSH equation output for a specific lift
S: Travel speed in inches per minute along the joint, the input crews most often miss
S-trap: A prohibited trap that drops vertically after the weir with no vent and siphons its own seal
Sacrificial mortar: Mortar kept softer and more vapor-open than the units so it takes the wear and lets the wall breathe
Sacrificial protection: A more reactive metal, such as zinc, corroding first to protect the steel
Saddle: A three- or four-point bend that jumps the run over something crossing its path
Safe working load (SWL): The rated load for a tie or shore, the breaking strength reduced by a built-in safety factor [https://anvilfield.com/field-guides/glossary/safe-working-load-swl/]
Safety glazing / hazardous location: Tempered or laminated glass meeting an impact standard, required by code in locations like doors, sidelites, low glass, and wet areas
Safety loop vs exit loop: A safety loop holds or reverses the gate over a vehicle; an exit loop opens the gate for a leaving vehicle
Safety relief valve: The ASME valve downstream of the PRV that opens to protect the low side if the PRV fails open
Safety switch: An enclosed disconnect with an external handle, fused or non-fused, rated by a NEMA enclosure type
Safety vs security film: Safety film retains fragments to protect people; security film delays forced entry, storm, and blast and needs anchoring
Safety wearable: A sensor worn on the worker that detects a hazard and alarms for help; it detects and alerts, it does not prevent the hazard
Salvageable vs non-salvageable: Whether an item can be restored for less than replacement, or is a documented total loss
Same-level fall: A fall onto the surface the worker is standing on, distinct from a fall to a lower level
Sampling hole / capillary: The drilled opening that draws the air sample, or a tube dropped off the pipe to place a sampling point exactly where smoke will be
Sand, cartridge, DE: The three filter media: sand (coarsest, backwashed), cartridge (mid, rinsed), DE (finest, backwashed and recharged)
Sand/oil interceptor: Garage device that settles sand and sediment and separates petroleum oil from floor-drain wastewater
Sanitization (Clear / Purge / Destroy): The NIST 800-88 levels of removing data so it cannot be recovered, from overwrite to physical destruction
Saponification: The reaction between the wet-chemical agent and hot grease that forms an oxygen-sealing soap foam
Sash: The movable front of the hood that shields the worker and sets the face velocity by changing the opening size
SAT: Site acceptance test, the Level 2 inspection of delivered gear against the approved submittal [https://anvilfield.com/field-guides/glossary/sat/]
Saturated load: Weight of the assembly with media at maximum water holding capacity, the number the structural engineer checks
Saturated steam: Steam at the temperature that matches its pressure; raise the pressure and the temperature rises with it
Saturated weight: The fully wet dead load of frame, media, plants, and water that the structure and attachment must carry
Saturation: The boiling or condensing state; saturation temperature is read from the refrigerant P-T chart at a measured pressure
Saturation efficiency: How close the cooler drives the air to the wet-bulb, as a percent of the full wet-bulb depression
Saturation temperature: The boiling or condensing temperature for a refrigerant at a given pressure, read from the P-T chart [https://anvilfield.com/field-guides/glossary/saturation-temperature/]
SAVE job plan: The six-phase study sequence from SAVE International: Information, Function Analysis, Creative, Evaluation, Development, Presentation
Saw-and-seal / cutback joint: Sawing a groove on the joint line after paving and sealing it, so the crack forms and stays sealed at a controlled line
Sawcut depth: The depth of the joint cut, commonly a quarter of the slab thickness
Sb: Allowable soil bearing capacity, in psf, from the geotechnical report
SBB / TGB: Secondary bonding busbar, one per telecom or equipment room, fed by the TBB
SBS: Styrene-butadiene-styrene, the rubber modifier; elastic, cold-flexible, torch, mopped, cold, or self-adhered
Scale: A hard mineral deposit, mostly calcium and magnesium hardness, that bakes onto hot surfaces and insulates them [https://anvilfield.com/field-guides/glossary/scale/]
Scaling: Flaking of the top 1/8 to 3/16 in from freeze-thaw and deicers on under-aired or over-finished concrete [https://anvilfield.com/field-guides/glossary/scaling/]
Scan-to-BIM: Modeling the point cloud into an existing-conditions BIM model, mostly manual with automation help
Scarify: To rip a smeared or over-compacted subgrade back open so it can infiltrate again [https://anvilfield.com/field-guides/glossary/scarify/]
SCBA: Self-contained breathing apparatus; carries its own breathing air for IDLH atmospheres
SCC: Self-consolidating concrete, flows and fills under its own weight with little or no vibration [https://anvilfield.com/field-guides/glossary/scc/]
SCCR: Short-circuit current rating: the maximum fault current the assembly can withstand, marked in kA at a stated voltage [https://anvilfield.com/field-guides/glossary/sccr/]
SCFM: Standard cubic feet per minute, the flow a pump moves at a reference condition
SCGF protection: Branch-circuit short-circuit and ground-fault device, sized off table FLC at the 430.52 percentage by device type
Schedule of values: The line-item breakdown of a subcontract that a pay application bills against by percent complete [https://anvilfield.com/field-guides/glossary/schedule-of-values/]
Schedule of values (SOV): The contract broken into billable line items that add to the contract sum; basis of the pay application [https://anvilfield.com/field-guides/glossary/schedule-of-values-sov/]
Scheduling multiplier: 1 divided by DULQ, the factor a run time grows by to bring the dry quarter up to its need
Scissor lift: Group A MEWP that raises a guardrailed platform straight up on crossed legs
SCM: Supplementary cementitious material such as fly ash, slag, or silica fume; a mineral addition, not a chemical admixture [https://anvilfield.com/field-guides/glossary/scm/]
Scope 1 / 2 / 3: Direct emissions, purchased-electricity emissions, and value-chain emissions under the GHG Protocol
Scope baseline: The original contract scope with inclusions and exclusions, the reference a change is measured against
Scope gap: Work no subcontract clearly assigns, so every trade assumes another owns it and nobody prices or builds it
Scour: Wind moving ballast off the roof, especially at the corners and perimeter, exposing the membrane and starting a peel
Scour velocity: The flush velocity, about 3.0 ft/s in recent C651 editions, that lifts and carries debris out instead of rinsing [https://anvilfield.com/field-guides/glossary/scour-velocity/]
SCR / DPF / DOC: Selective catalytic reduction for NOx, diesel particulate filter for PM, oxidation catalyst for CO
Scratch: Temporary high-speed working space for a running job, often on local or hot-tier flash, not meant to persist
Screed / strikeoff: Bringing fresh concrete to grade and a flat plane right after placement, before finishing
Screw dimple / screw pop: A dimple is the shallow set of a correctly driven screw below the paper; a pop is a fastener telegraphing through the finish, usually from a broken-paper or loose screw
Screw jack: An adjustable base that levels each leg so the scaffold stands plumb on uneven grade
Scribe rail / filler: The oversized or sacrificial piece left long on the wall side specifically to be cut to fit
Scribing: Transferring a wall or floor profile onto the cabinet and cutting to it so the gap closes
Scupper: An opening through a parapet that drains water off the roof edge, sized as a weir
SD / DD / CD: Schematic design, design development, and construction documents, the staged design sets from concept to buildable
SD-WAN: Software-defined WAN that ties multiple links together and fails over between them automatically
SDC: Seismic design category, the ASCE 7 classification that drives whether and how a system is braced [https://anvilfield.com/field-guides/glossary/sdc/]
SDI / SDD: Subsurface drip irrigation, dripline buried below the surface, commonly 4 to 6 in deep for turf
SDS: Separately derived system, a transformer or neutral-switched generator that establishes its own ground reference [https://anvilfield.com/field-guides/glossary/sds/]
Seal class (A, B, C): The construction instruction for where to apply sealant, set by the duct pressure class
Seal class (A/B/C): What must be sealed: A is everything, B is joints and seams, C is transverse joints only [https://anvilfield.com/field-guides/glossary/seal-class-a-b-c/]
Seal flush: A clean water stream piped to the seal faces to cool them and wash away grit on dirty or hot service
Seal-in / holding contact: The auxiliary contact that keeps the coil energized after the start button is released
Sealant joint: The sealed joint at openings on EIFS; a maintenance item that has to be re-sealed on a cycle
Sealcoat: A thin protective surface coating of coal tar or asphalt emulsion that blocks UV and water [https://anvilfield.com/field-guides/glossary/sealcoat/]
Seam clamp: A non-penetrating bracket that grips a standing seam with set screws, adding no holes to the panel
Seam probe: A non-destructive test drawing a blunt tool along a cooled weld to find voids and cold welds
Seasonal adjust: A controller percentage that scales every zone up or down as plant demand changes through the year
Seasonal adjust / water budget: A controller percentage that scales every run time up or down as plant demand changes through the year
Seasonal color: The planting and rotating of annual flowers in high-visibility beds and containers several times a year for continuous, fresh bloom
Seasonal cutoff: The agency date after which surface paving stops or requires special approval, set by climate and spec
Secant / tangent pile wall: A wall of overlapping (secant) or touching (tangent) drilled concrete piles, stiff and low-vibration, and watertight when secant.
Second-look lender: A backup program that approves customers the primary lender declines
Secondary / auxiliary drain pan: The backup pan under equipment that catches water when the primary drain fails
Secondary / overflow drainage: The independent backup, inlet set about 2 in above the low point, for a blocked or overwhelmed primary
Secondary / overflow piping: The independent storm piping for the overflow drains or scuppers, separate from the primary and discharging above grade
Secondary containment: The double wall, dike, or basin that catches fuel when the primary tank or piping leaks
Secondary containment / interstitial: A second wall around tank and piping, with a monitored interstitial space between the walls that holds a primary leak
Secondary FLA: Rated current on the secondary side, off the secondary voltage, sizes the secondary conductors and panel
Secondary injection: Injecting simulated current into a relay or trip unit's inputs to confirm it picks up and times out at its setting, without energizing the primary system
Secondary overflow: Independent emergency drainage set above the detention depth, sized for the design storm if the restrictor clogs
Sediment: Mineral and scale that settles on the tank bottom and insulates the heat source
Sediment basin: A built pond sized by drainage area that holds runoff and dewaters slowly so dirt settles out before discharge
Sediment control: Measures that capture soil already moving, such as silt fence, inlet protection, and sediment basins
Sediment trap: A capped vertical leg that catches debris before the burner orifice
SEER2 / HSPF2: Season-long cooling and heating efficiency ratings under the current DOE test method [https://anvilfield.com/field-guides/glossary/seer2-hspf2/]
SEER2 / IEER: AHRI efficiency ratings for seasonal and part-load cooling that proper charge and airflow protect
Segmentation: Tagging customers so you can pull a targeted list, such as every roof over 20 years old in one area
Segregation: Non-uniform separation of coarse and fine aggregate (physical) or cold lumps in the mat (thermal) [https://anvilfield.com/field-guides/glossary/segregation/]
Segregation resistance: The mix staying uniform while and after it flows, read on the VSI and settlement tests
Seismic / isolation joint: A wide separation between building sections so they can sway independently in an earthquake without pounding
Seismic anchorage / Ip: The restraint tying equipment to the structure; Ip is the component importance factor, commonly 1.5 for essential facilities
Seismic bracing / compression post / splay wire: The lateral restraint for a code seismic ceiling: a post resisting upward push and splay wires resisting sideways sway
Seismic hook: A 135-degree hook with a 6db extension, but not less than 3 in, anchoring a tie around a longitudinal bar
Seismic joint: An expansion joint sized for the large, multidirectional movement of a seismic event, rated to the structural engineer's design
Selective coordination: Only the OCPD nearest the fault opens, leaving every upstream device closed, across the full range of available overcurrents [https://anvilfield.com/field-guides/glossary/selective-coordination/]
Selective demolition: Removing specific parts of a building, usually the interior and finishes, while the structure stays standing. Also called interior strip-out.
Self-adhered membrane: Peel-and-stick rubberized asphalt or butyl sheet that is waterproof and seals around fasteners, the ice and water shield
Self-closing gate: Gate at a ladderway opening that swings away from the hole and closes itself
Self-contained enclosure: An all-in-one box holding the rack, cooling, power, monitoring, and security, needing no data center room
Self-contained vs CT metering: Full current through the meter vs current transformers stepping it down for larger services
Self-flashing: Foam sprayed continuously up and around penetrations as its own monolithic flashing
Self-leveling / non-sag: Pourable grade P for horizontal joints versus gunnable grade NS for vertical and overhead joints
Self-regulating cable: Parallel cable whose output rises in cold and falls when warm; cut to length, overlaps safely
Self-scouring velocity: The flow speed, near 2 ft per second, that keeps solids moving instead of settling and damming the line
Self-supporting ladder: A ladder that stands on its own, such as a step ladder opened into an A-frame with spreaders locked
Self-test / auto-monitoring: A GFCI's built-in periodic check of its own ability to trip, required under UL 943 since 2015
Semi-annual: The every-6-months service by a trained technician, distinct from the monthly owner inspection
Semi-instantaneous: A small built-in volume with fast recovery, often paired with a buffer tank
Semi-permanent patch: Square, clean, dry, tack, fill in compacted lifts, seal the edge over a sound base
Semi-rigid filler: A hard epoxy or polyurea that supports a traffic joint edge but does not move with the joint
Semi-rigid joint filler: A polyurea or epoxy that cures firm to support joint edges, commonly Shore A 80 or higher
Semicon: The thin semiconducting layer over the conductor and over the insulation that smooths the field and sets the equal-stress condition
Semiconducting shield (semicon): The conductive-but-not-metallic layers over the conductor and over the insulation that keep the field uniform; the insulation shield must be removed cleanly at an end
Sensible / latent: Heat that changes temperature versus heat tied up in moisture
Sensible cooling: Cooling that lowers air temperature without removing moisture, the mode an in-row unit runs when the coil stays above dew point [https://anvilfield.com/field-guides/glossary/sensible-cooling/]
Sensible heat: The heat that changes a fluid's temperature; how single-phase cooling carries its load
Sensible heat ratio: The fraction of a cooling load that is temperature versus moisture, which sets how the DOAS and parallel system split the work
Sensible heat ratio (SHR): Sensible cooling divided by total cooling; the slope of the coil process line
Sensible load: The temperature load, the heat that changes air temperature without changing its moisture content
Sensible vs latent: Sensible cooling lowers air temperature; latent cooling removes moisture. Beams do sensible; the DOAS does latent
Sensing cable: Leak detection rope that detects water anywhere along its length and, on addressable systems, reports the distance to the leak
Sensor drift: A sensor slowly reading off true, so the controller holds the wrong condition and the analytics decide on bad data
Sensor grade / calibration / drift: Grade is the accuracy class from consumer to reference; calibration corrects the reading to a known value; drift is the gradual error a sensor develops as it ages
Sentinel flush: An automatic timed flush on a sensor valve that keeps the trap seal from drying out when a fixture sits unused.
SEOR: Structural engineer of record, who assigns Ip, runs Fp, and stamps the anchorage and bracing design
Separated / sealed combustion: A gas unit that ducts combustion air from outdoors and vents flue products out, isolating the burner from room air
Separately derived system: A source, such as a generator behind a switched-neutral transfer switch, that needs its own single neutral-to-ground bond per NEC 250.30 [https://anvilfield.com/field-guides/glossary/separately-derived-system/]
Separately derived system (SDS): A power source with no direct electrical connection, including through the neutral, to another supply; gets its own neutral-ground bond and electrode
Separation: Keeping two dissimilar layers, the clean aggregate and the fine subgrade, from mixing under load.
Separator: A device upstream of the PRV that removes entrained water so the valve gets dry steam
Septic system: Onsite wastewater system that treats sewage on the property where there is no public sewer, using a tank and a soil drainfield
Septic tank, scum, sludge: Buried watertight tank that settles solids (sludge, on the bottom) and floats grease (scum, on top), passing clarified effluent to the field
Sequence of operation: The fixed order a furnace fires in, each step proving itself before the next runs
Sequential footage marker: The running number printed every couple of feet, ascending or descending
Service agreement: A recurring maintenance contract that keeps you on the equipment on a schedule, cutting no-maintenance failures and false callbacks while adding predictable revenue between installs. [https://anvilfield.com/field-guides/glossary/service-agreement/]
Service conditions: The building at its design temperature and humidity, HVAC running, before and during the test
Service contract: The ongoing maintenance agreement for pruning, plant replacement, irrigation checks, and fertigation that keeps the wall alive
Service disconnecting means: The switch or breaker nearest the entrance that disconnects the whole service
Service drop / lateral: The utility's overhead (drop) or underground (lateral) conductors landing at the building
Service entrance conductors: The customer's conductors from the utility connection to the service disconnect
Service factor: Nameplate multiplier of thermal margin; 1.15 or higher allows the overload at 125 percent instead of 115 percent
Service factor (SF): The continuous overload margin, such as 1.15 for 15 percent over rated
Service life: How long a pavement carries traffic before it needs a major structural rehabilitation
Service loop: Deliberate slack coiled at a termination so the cable can be serviced or the gear moved
Service upgrade: Raising the amperage of the whole service: utility feed, meter, main, conductors, and grounding
Service-entrance rated: Gear built and labeled to serve as the service disconnect and carry the main bonding jumper
Set retarder: An admixture (ASTM C494 Type B or D) that slows hydration to extend working time in the heat
Set window: The span when the surface is firm enough to work but not too hard, read by the footprint test
Setback: Minimum code distance from the system to wells, surface water, property lines, and buildings to protect drinking water [https://anvilfield.com/field-guides/glossary/setback/]
Setback / batter: The per-course step back (setback) and the resulting lean into the hill (batter) that bias the wall's weight over the soil
Setpoint: The outlet temperature the valve is field-adjusted to hold under varying inlet conditions [https://anvilfield.com/field-guides/glossary/setpoint/]
Setting blocks: Load-bearing pads under the glass at the quarter points that carry the weight and hold the edge up out of the drainage pocket
Severity (Sev1 to Sev4): The classification of how bad an incident is, by impact and scope, that drives the size and speed of the response; the scale is the operator's to define
Severity / extent: How bad a distress is (low, medium, high) and how much of the section it covers (area or linear feet) [https://anvilfield.com/field-guides/glossary/severity-extent/]
Sewage ejector: A solids-passing sewage pump, distinct from a grinder that cuts solids and an effluent pump that handles low-solids liquid [https://anvilfield.com/field-guides/glossary/sewage-ejector/]
Sewer gas: The mix of gases in a drainage system, including hydrogen sulfide, methane, and ammonia, that smells foul and is toxic and flammable at high concentration
SF: Safety factor on the bearing, commonly about 1.5
SFCA: Square feet of contact area, the unit for formwork, measured on the form face that touches the concrete
SFRA: Sweep frequency response analysis, a winding and core fingerprint that reveals mechanical movement
SFRM: Spray-applied fire-resistive material, a cementitious or gypsum spray with fiber, for concealed steel and decks
Shadowing: Voids or sand pockets behind reinforcing steel from shooting straight at the bar instead of behind it
Shaft grounding ring: Conductive-microfiber ring that diverts shaft current to the frame around the bearing
Shape code: A standard code naming the bend shape, with bend dimensions labeled A, B, C and so on
Shape factor: The depth-to-width ratio of a joint sealant, set by the reservoir cut and the backer rod
Shared coordinate origin: The one survey point and coordinate system every model references, so the models line up when federated
Shared neutral: The single grounded conductor common to all the hots of an MWBC, carrying the imbalance
Shear slump: A lopsided slump where the top slides off to one side; retest on a fresh portion
Sheave / pulley: The grooved wheel a V-belt rides in; driver on the motor, driven on the fan
Sheet flow: A thin, broad film of water moving evenly across a surface, the gentle flow grading tries to keep, versus concentrated flow that erodes
Sheet piling: Interlocking steel sheets driven to form a continuous, near-watertight wall for soft or wet soil.
Sheet vinyl: Wide vinyl sheet with heat-welded seams, the impervious floor for healthcare and clean spaces
SHGC: Solar Heat Gain Coefficient, 0 to 1, the fraction of solar heat that gets through; lower rejects more heat [https://anvilfield.com/field-guides/glossary/shgc/]
SHI: Supply Heat Index; the fraction of heat the supply picks up before reaching the inlet
Shield / trench box: A structure that protects the worker inside it if the wall collapses; it does not hold the soil
Shift handoff (pass-down): The structured transfer at shift change, a written log plus a verbal briefing, that carries open issues and plant state from one crew to the next.
Shipping split: A factory-divided segment of a lineup that ships as one piece and is field-joined on site
Ships / alternating-tread ladder: Steep stair-ladder, commonly 50 to 70 degrees, used where a standard stair will not fit
Shock pad: An elastic layer under synthetic turf that provides cushioning as the infill compacts over time
Shootability vs pumpability: The stiffness to hold on a wall or overhead versus the flow to move through the hose
Shore / reshore: A shore carries fresh-slab load to a lower level; a reshore is reset after stripping to spread later construction loads across floors
Shoring: A support system, often hydraulic, that holds the trench walls in place
Short circuit: Any rigid path bridging the isolator that carries vibration into the structure
Short circuit / fault: A sudden high current through an unintended low-impedance path
Short load: An order below the plant minimum, which carries a short-load fee [https://anvilfield.com/field-guides/glossary/short-load/]
Short-time / short-circuit rating: The fault current MV switchgear withstands and interrupts, in kA symmetrical, per the submittal
Shorting block: The terminal block that lets a CT secondary be safely shorted before it is opened
Shotcrete / gunite: Pneumatically applied concrete or mortar; gunite is the dry-mix process, mainly in the pool trade
Shotcrete / gunite shell: The pneumatically applied, steel-reinforced concrete pool structure. Gunite is the dry-mix process, where water is added at the nozzle; pool shotcrete usually means the wet-mix process, batched with water and pumped.
Shower pan / pan liner: The waterproof barrier under and around the shower; the sheet liner in the traditional method
SHR: Sensible heat ratio, sensible load divided by total load
Shrink: Inventory that disappears without a record, from off-ticket use, transfers, or loss, measured as a percent of value [https://anvilfield.com/field-guides/glossary/shrink/]
Shrink and swell: The change in soil volume between bank, loose, and compacted states that throws off cut and fill balance
Shrink-wrap: Heat-shrink film drawn tight over a roof or structure as a continuous temporary cover with few seams, an alternative to tarps for larger or longer-term securement
Shroud: The hood or guard around the wheel or bit that forms the capture zone feeding the dust collector, sized to the tool
Shunt trip: The trip coil that opens a breaker on a control signal, which is how an EPO button drops the load
Sick building syndrome: A pattern of acute comfort and health complaints tied to a building with no specific illness or cause identified
Side flash: A spark jumping from the LPS to nearby grounded metal at a different potential during a strike
Side-stream filtration: A slipstream off the main flow run through a fine filter that polishes the whole loop volume over time
Sidecar power: A separate power rack that rectifies AC to DC and feeds one or more compute racks over a DC bus, freeing rack space for compute
Siding / cladding: The exterior wall covering that sheds the bulk of the rain; the building's raincoat, not a watertight skin
Sign disconnect (NEC 600.6): A disconnecting means within sight of the sign, or lockable open, so a worker can kill and verify the power
Sign permit / zoning: The local approval and ordinance controlling sign area, height, setback, illumination, brightness, and count
Sign-off: The customer signature that accepts the work and authorizes the bill
Signal reference grid: A bonded copper grid under data center equipment that holds the floor at a common potential [https://anvilfield.com/field-guides/glossary/signal-reference-grid/]
Signal reference grid (SRG): An under-floor copper mesh bonded to building ground that ties the floor and gear to a common reference
Silane / siloxane: Penetrating, breathable water repellents that bond in the pores; silane penetrates deeper, siloxane suits more porous concrete
Silicate densifier: A lithium, sodium, or potassium silicate that reacts with free lime to harden and dust-proof the surface; not a water repellent
Silicon photonics: Optical components built directly in silicon by chip fabrication, the basis for dense optical integration and co-packaging
Silicosis: Permanent, incurable scarring of the lungs from inhaled respirable crystalline silica, in acute, accelerated, and chronic forms
Silt fence: A trenched-in fabric barrier on the downslope edge that ponds runoff so sediment settles before water leaves the site
SIMOPS: Simultaneous operations, construction work alongside live, energized, or occupied systems in the same building
Simple payback: Installed cost divided by annual dollar savings, the years to recover the cost; the common ranking screen.
Simultaneous disconnect: A means to open all the ungrounded conductors at once, by handle tie or multipole breaker
Simultaneous heating and cooling: One system heating air another system just cooled, a classic and costly waste FDD targets [https://anvilfield.com/field-guides/glossary/simultaneous-heating-and-cooling/]
Single interlock: Pre-action that admits water to the pipe on detection alone; a sprinkler still has to fuse for water to flow
Single maximum: The older sequence with one fixed minimum that doubles as the heating airflow, so the minimum runs high
Single overcurrent device: One breaker or one set of fuses at the end of a tap, rated at or below the tap ampacity, that protects it downstream
Single source of truth: One record per customer that everyone works from, so no conflicting copies exist in phones and spreadsheets [https://anvilfield.com/field-guides/glossary/single-source-of-truth/]
Single vs double interlock: Single admits water on detection alone; double requires both detection and a fused sprinkler head before water enters the pipe [https://anvilfield.com/field-guides/glossary/single-vs-double-interlock/]
Single vs twin mast: One mast carrying a cantilevered deck, or two synchronized masts carrying one long continuous deck
Single zone / multi-zone: One condenser feeding one head, versus one condenser feeding several independent heads
Single-bolt joint: A busway joint clamped by one high-strength bolt and conical spring washers, often with a twist-off or visual torque indicator
Single-mode (SM): Fiber with a ~9 micron core carrying one mode, low loss, long reach, laser source, graded OS1/OS2
Single-mode / multimode: Single-mode (~9 micron core) carries one path far; multimode (~50 micron core) carries many paths a shorter way
Single-phase / two-phase: Coolant stays liquid (single-phase) or boils on the cold plate (two-phase)
Single-phase cooling: Cooling where the liquid stays liquid and carries heat as a temperature rise (sensible heat), the mature default
Single-phase immersion: Immersion where the dielectric fluid stays liquid and is pumped or convected past the hardware to a heat exchanger
Single-phasing: Loss of one of three supply phases while the motor runs, overheating the remaining windings fast
Single-ply: A low-slope membrane in a single sheet, TPO, EPDM, or PVC, seamed welded or taped into a continuous skin
Siphonage: The loss of a trap seal pulled down the drain when a fixture drains without adequate venting
Site datum vs building grid: The real-world coordinate system and elevation datum versus the architect's column-line grid, related by an origin and a rotation
Site logistics plan: The layout and rules for moving people, material, and equipment on the site; also called a site utilization plan or construction logistics plan (CLP)
Site selection: The structured evaluation of candidate sites against power, water, connectivity, land, climate, hazard, and policy
Site WUE: WUE counting only the water used on-site, mostly cooling water, divided by IT energy
Skidmore: Skidmore-Wilhelm tension calibrator that reads actual bolt tension for verification
Skimmer: Surface filter at the water line that catches floating debris and houses or pre-filters the pump
Skin friction (side resistance): Load shed into the soil along the sides of the shaft through friction and adhesion over its length
SLA: Service-level agreement, the response-time commitment and its remedy on a commercial contract [https://anvilfield.com/field-guides/glossary/sla/]
SLA / response time: The contracted time within which you must respond to a call, often tiered by priority
Slab on grade / slab on ground: A concrete floor cast directly on the prepared soil and supported continuously by it
Slab RH (ASTM F2170): Internal relative humidity of the slab at depth, the moisture limit most specs use
Slab-on-grade: The structural concrete floor the racks sit on directly, with power, cooling, and cabling run overhead
Slab-on-grade vs elevated: A ground-floor slab bearing on soil versus a structural floor carried by beams and columns on upper levels
SLAM / take-5: The individual last-minute risk check at the task: stop, look, assess, manage, in about a minute
Slate grade (S1, S2, S3): ASTM C406 classification by expected service life: S1 over 75 years, S2 40 to 75, S3 20 to 40
Slate hook: A copper or stainless hooked fastener driven into the deck to hold a replacement slate without a face nail
Slate ripper: A long hooked steel bar slid under a broken slate to cut or pull its hidden nails for removal
SLC: Signaling line circuit, the addressable data loop the panel polls device by device
SLD / one-line: Single-line diagram, one line and symbols representing the whole power system
Slide valve: The continuous capacity control on a screw compressor, delaying where compression begins
Sling angle: The angle of a sling leg from horizontal; lower angles raise leg tension by 1 divided by the sine of the angle
Slinger ring: Ring on the outdoor fan that throws condensate onto the condenser coil to evaporate it
Slip: The gap between synchronous and full-load speed that lets the motor make torque
Slip form: A short form raised continuously during a non-stop pour to build tall monolithic structures with no horizontal joints
Slip lining: Pushing or pulling a smaller new pipe inside the host and grouting the annulus
Slip sheet / protection pad: The wear-and-compatibility layer between a ballasted rack foot and the roof membrane
Slip vs trip: A slip is loss of traction; a trip is the foot catching an object or a level change
Slip-critical: Pretensioned joint that carries load by friction across a prepared faying surface
Slip-form curb: Curb and gutter extruded continuously through a machine mold, no stationary forms to set or strip
Slippage cracking: Crescent-shaped cracks from a thin top layer shoving on a poor bond, a tell-tale of bad tack
Slit seeding (slice seeding, power seeding): Cutting furrows and dropping seed into them for direct soil contact and high germination
Slope (in per ft): Roof fall in inches of rise per foot of run; 1/4 in per ft is about 2 percent, the common drainage minimum
Slope (percent): Vertical fall over horizontal run times 100; 2 percent is 1/4 in per foot, or 2 ft of drop in 100 ft
Slope (pitch): Rise over run in inches per foot, such as 4:12, which drives single, double, or membrane underlayment
Slope / grade: Fall per length, given as inches per foot or percent; 1/8 in per ft is about 1 percent
Slope / pitch: Rise over run in inches per foot, written like 4:12; the slope decides the steep-slope versus low-slope family [https://anvilfield.com/field-guides/glossary/slope-pitch/]
Slope factor / pitch multiplier: The number the footprint is multiplied by to get the true sloped roof area
Slope ratio (H:V): Horizontal run to vertical rise of a cut wall; a flatter number is a wider, safer cut [https://anvilfield.com/field-guides/glossary/slope-ratio-h-v/]
Slow-release fraction: The percent of the nitrogen that is coated or water-insoluble and meters out over weeks
SLU: Self-leveling underlayment, a flowable cement or gypsum topping poured to flatten a slab for finish flooring
Slug method: Passing a short, heavily dosed slug through a large main for a short contact time
Slump: The drop in height of fresh concrete after the cone is lifted, a measure of consistency and workability [https://anvilfield.com/field-guides/glossary/slump/]
Slump flow: Average spread diameter of the SCC patty after the cone lifts, the SCC measure of filling ability [https://anvilfield.com/field-guides/glossary/slump-flow/]
Slump life: How long a mix stays placeable before it stiffens, short on heavy superplasticizer doses and in heat
Slurry: The alkaline water-and-concrete mix from wet cutting that must be contained, not drained
Slurry (mineral / polymer): Drilling fluid that holds the wall, either bentonite clay (mineral) or a water-based synthetic (polymer)
Slurry / diaphragm wall: A reinforced concrete wall cast in a slurry-supported trench, the deepest and most watertight system, often permanent.
Slurry seal: A thin cold mix of conventional asphalt emulsion, fine aggregate, mineral filler, and water that seals a sound surface and cures by evaporation
Slurry seal vs micro-surfacing: Cold emulsion-aggregate seals; micro-surfacing is always polymer-modified, cures chemically, reopens faster, and can fill minor ruts
SMA: Stone matrix asphalt, a gap-graded mix with a stone-on-stone skeleton for rut resistance
Smart / ET controller: A controller that sets run time from local weather and evapotranspiration instead of a fixed clock
Smoke damper (SD): Closes on a smoke signal to limit smoke through a smoke barrier; listed to UL 555S, leakage-rated
Smoke test: A diagnostic that pressurizes the DWV system with visible smoke to reveal where the barrier is broken
SMR: Small modular reactor, the long-horizon firm carbon-free option contracted through PPAs and co-location
SN: Structural number: the total structural strength AASHTO 93 says the section needs over the subgrade
Snaking / cabling / rodding: Running a cable machine through the line to open a clog
SNAP: EPA Significant New Alternatives Policy, which lists acceptable substitute refrigerants
Snap-lock vs mechanical seam: Snap seams press together by hand; mechanical seams are folded closed by a powered seamer [https://anvilfield.com/field-guides/glossary/snap-lock-vs-mechanical-seam/]
Snow load: The design weight of snow a solid or closed-louver roof must carry, from ASCE 7 by site
Snow rail / snow fence: A continuous bar, pipe, or fence across the slope on brackets that holds a large snowpack on one line
Snow retention: Guards or rails fixed to the roof that hold snow so it melts off gradually instead of releasing in a slab
Snow retention / snow guard: Devices fixed to the roof that hold the snowpack so it sheds slowly instead of avalanching off
Snow sensor: Control that runs the system only when moisture and cold are both present
Snow-melt class: ASHRAE classification (I, II, III) for how completely a surface must stay clear
Snubber: A restraint that allows normal vibration but catches isolated equipment in a quake
Snug-tight: Plies brought into firm contact by full effort on a spud wrench or a few impacts
Snug-tight vs pretensioned / slip-critical: Snug brings plies into firm contact; pretensioned and slip-critical bolts are tightened to a high specified tension, with slip-critical adding a faying-surface requirement
SOC: Security operations center, the staffed room that watches and dispatches the response [https://anvilfield.com/field-guides/glossary/soc/]
SOC / SOH: State of charge, the energy left now; state of health, the capacity lost to age
Sod (turf, sod roll, slab): Mature grass grown on a farm and harvested with soil and roots for transplant
Sodic soil: Clay whose structure has collapsed from excess sodium, the narrow case where gypsum helps
Sodium hypochlorite (SH): The soft-wash biocide, the same active ingredient as bleach at higher strength, that kills organic growth
SOFC: Solid-oxide fuel cell, converting natural gas or hydrogen to electricity without combustion
Soffit: The panel closing the underside of the overhang, often vented for attic intake
Soft clash: A clearance violation where elements are too close, leaving no access, insulation, or service room, even though they do not touch
Soft foot: A machine foot that does not sit flat, so tightening its bolt distorts the frame and ruins the alignment; correct it first
Soft pull / hard pull: A prequalify check that does not affect the score, versus the full application check that does
Soft washing: Cleaning delicate surfaces at low pressure with a cleaning solution that kills mold, algae, and mildew at the root
Soft-close: Hardware with a damper that pulls a door or drawer quietly closed and keeps it from slamming
SOH: State of health, the battery's capacity now versus when it was new
Soil compaction: Soil packed dense enough to squeeze out the pore space roots need for air and water, the number one urban tree stressor
Soil gas: The air in the pore spaces of the soil under and around a building, carrying radon or contaminant vapors
Soil nailing: Grouted steel bars drilled into the cut face with a shotcrete facing, built top-down in cohesive soil that stands on a cut.
Soil resistivity: A property of the soil itself, in ohm-meters or ohm-centimeters; the input that drives ground resistance [https://anvilfield.com/field-guides/glossary/soil-resistivity/]
Soil structure: How particles clump into aggregates and pore space; built by organic matter, wrecked by compaction and wet tillage
Soil texture: The ratio of sand, silt, and clay, which sets drainage and water holding and does not change with amendment
Soil-moisture sensor: A buried sensor reading volumetric water content in the root zone; the controller bypasses a cycle when the soil is above the threshold
Soiling: Loss from dust, pollen, droppings, pollutants, or snow on the module glass blocking light, commonly 4 to 7 percent of annual energy and far higher in dusty climates
Solar PV O&M: Operations and maintenance of a photovoltaic plant: monitoring production and doing the preventive and corrective work that keeps it producing over a 25-to-30-year life
Solar reflectance (SR / albedo): Fraction of solar energy a surface reflects, on a 0 to 1 scale; higher reflects more sun
Solar-cellular standalone: A self-contained unit powered by solar and battery that sends video over cellular, for sites with no power or internet
Solar-control film / SHGC / VLT: Film that rejects solar heat, UV, and glare; SHGC is the heat-gain fraction, VLT the visible-light percent
Solar-ready / PV-ready: A roof and building designed so a future PV array can be added without a tear-up, with capacity, zone, and pathway reserved
Solar-ready zone: The designated, clear, unshaded roof area reserved for the future solar array
Soldering / sweating: Joining copper by drawing lead-free solder into a clean, fluxed, heated joint by capillary action
Soldier course: A border of pavers stood so the long side runs perpendicular to the edge; a sailor course runs parallel
Soldier pile and lagging: Vertical H-piles at intervals with lagging spanning between them, a discrete, non-watertight wall for firm soil above the water table.
Solid-core CT: A closed-ring current transformer the conductor threads through, more accurate, used when the circuit is open
Solids-handling vs grinder pump: A solids-handling pump passes whole solids around 3 in through a non-clog impeller; a grinder pump cuts solids to a slurry for a small, high-head force main
Solvent weld: Chemically fusing PVC, CPVC, or ABS with primer and the cement listed for that plastic, not gluing [https://anvilfield.com/field-guides/glossary/solvent-weld/]
Sonde: The transmitter inside the camera head that a surface locator homes in on
Sone: The loudness rating on small fans; lower is quieter, with 1 to 2 sones quiet for a restroom fan
SOO: Sequence of operations, the written definition of setpoints, staging, modes, interlocks, alarms, and failure response the controls must follow [https://anvilfield.com/field-guides/glossary/soo/]
Soot: The acidic particulate residue smoke leaves on surfaces, which corrodes and etches if not removed
Soot corrosivity: Soot is acidic and corrodes metal, etches glass, and stains finishes if it is left to sit
SOP: Standard operating procedure, the standing procedure for routine, repeatable operations
SOP, MOP, EOP: The three written procedure types: standard operating procedure for routine running, method of procedure for a specific task, emergency operating procedure for failures.
Sound power (Lw) vs sound pressure (Lp): Lw is the source's emission, what manufacturers rate; Lp is the level measured at a location
Source removal: Physically removing the soot and char before any air treatment, because you cannot deodorize over the source [https://anvilfield.com/field-guides/glossary/source-removal/]
Source WUE: WUE that adds the off-site water used to generate the electricity the facility consumes
SOV (specified overall value): The F-number required for the whole placement, the composite across all test sections
Spaced sheathing / breathing assembly: Open 1x boards or a ventilated air space that lets the underside of the cedar dry, so the wood does not rot
Spacer: Manufactured base and intermediate pieces that hold the conduit grid at the specified center-to-center spacing
Spacing factor: Average distance from any point in the paste to the nearest air void; a small value indicates a durable system
Spall: A fragment of concrete that has broken or flaked off the surface, usually over corroding steel
Spalling: Cracking and flaking of unit faces, the classic damage from trapping moisture and stress with too-hard mortar [https://anvilfield.com/field-guides/glossary/spalling/]
Spark screen / arrestor: A mesh over a fire pit or at a chimney top that stops embers from escaping
SPCC: Spill Prevention, Control, and Countermeasure plan under EPA 40 CFR 112 for aboveground oil over 1,320 gallons aggregate [https://anvilfield.com/field-guides/glossary/spcc/]
SPD: Surge protection device, which clamps the transient on building wiring that the LPS itself does not address [https://anvilfield.com/field-guides/glossary/spd/]
Special / acid / chemical waste: Corrosive or chemically hazardous drainage that cannot enter a normal drain or the sewer untreated
Special inspection: A code-required inspection of specific structural work by a qualified, independent inspector, reported to the building official under IBC Chapter 17 [https://anvilfield.com/field-guides/glossary/special-inspection/]
Specific capacity: Well yield per foot of drawdown, for example 1 gpm per foot
Specific surface: The surface area of the air voids per unit volume of air; higher means finer, more protective bubbles
Specific volume: Cubic feet occupied per pound of dry air; the inverse of density, used to correct for altitude
Speech intelligibility / STI: How much of a spoken message a listener can understand, reported on the Speech Transmission Index or Common Intelligibility Scale
Speed ratio: Motor sheave PD divided by fan sheave PD, the factor that sets fan RPM from motor RPM
Speed to lead: How fast you respond after a lead arrives; minutes, not hours, and the first credible response usually wins
Speed to lead / first-response time: How fast you respond to a new inquiry; faster usually wins the job because most customers contact several companies and hire whoever answers first
SPF: Spray polyurethane foam, a sprayed monolithic low-slope roof that insulates and waterproofs, protected by a coating [https://anvilfield.com/field-guides/glossary/spf/]
Spider box: A portable, listed temporary power distribution box that splits one feeder into several GFCI-protected receptacles
Spiff: A small incentive bonus paid for a specific result, such as a sold maintenance agreement
Spike aeration: Punching holes with solid tines without removing soil, which can pack compacted ground tighter
Spiked roller: A roller that breaks surface tension to release entrained and outgassing air from the wet pour
Spill and overfill prevention: A catchment basin at the fill for hose drips, plus a shutoff or alarm that stops a delivery before the tank overruns, commonly at 90 to 95 percent
Spillage / backdraft: Exhaust rolling out of the draft hood, or the vent flow reversing, both putting combustion gas in the room
Spillway / weir: The lip the water sheets over at a waterfall, measured in width, which sets the pump GPH
Spine: The fabric layer that forwards traffic between leaves; connects to no servers and no other spine
Spiral duct: Round duct made from a strip locked into a helical seam that stiffens it
Splice: A connection joining one conductor to another, as opposed to a termination
Splice fill: Conductors plus splices and taps at one point, held to 75 percent of the area, kept accessible
Splice plate: A concealed backer with sealant strips under a coping joint that seals it while allowing thermal movement
Splice tape: Factory-extruded butyl tape that joins two EPDM surfaces into a seam over a splice primer
Split-case pump: A base-mounted pump that splits along the shaft for in-place service, with a double-suction impeller that balances thrust
Split-core CT: A hinged current transformer that clamps around a live conductor for retrofit without a shutdown
SPOF: Single point of failure: one component or path whose loss drops the load
Spoon-feeding: Light, frequent fertilizer applications instead of one heavy dump
Spot / point sensor: A fixed sensor at one high-risk place, a fitting, tray, low point, or CDU pan, for an early targeted catch
Spot detector: Point sensor that detects water at one fixed location, used in pans, at drains, and at low points
Spotter: A dedicated ground worker, clear of the path, who guides a machine through a move the operator cannot see safely, on hand signals or radio, and stops the move the moment the line of sight is lost. [https://anvilfield.com/field-guides/glossary/spotter/]
Spray injection: Truck-mounted method that blows the hole clean and sprays tack and emulsion-coated aggregate
Spread: The diameter the concrete flows to, reported to the nearest 1/2 in under ASTM C1611
Spread and drop: How wide the supply pattern fans out (spread) and how far a cold stream falls as it travels (drop)
Spread footing: A pad under a column that spreads a point load into the soil; also isolated or pad footing
Spread rate: About 110 lb of asphalt per square yard per inch of compacted depth at roughly 145 lb/cf
Spreader bar: Rigging that spreads the crane pick across several lift inserts so no single insert is overloaded
Springback: The few degrees a bend relaxes open when pressure releases, corrected by overbending
Spud: The threaded fixture connection the flushometer tailpiece seals into; larger on water closets than urinals.
Square: 100 square feet of sloped roof area, the unit roofing is measured, ordered, and priced in [https://anvilfield.com/field-guides/glossary/square/]
Square root of three: 1.732, the factor from 120-degree spacing that links line and phase values and appears in three-phase power
Square yard (SY): Nine square feet; the unit paving is bid and paid in
SR / DR / FR / LR: Optic reach classes: SR short multimode, DR and FR longer single-mode, LR longer still
SR / LR / FR / DR: Transceiver reach families; SR short-reach multimode, LR/FR/DR single-mode
SR4 / DR4 / SR8: IEEE 802.3 parallel PMDs: SR4 and DR4 are 8-fiber (4 Tx + 4 Rx), SR8 is 16-fiber (8 Tx + 8 Rx)
SRG: Signal reference grid, the bonded mesh a data center uses instead of isolated grounds for a high-frequency reference
SRG / CBN: Signal reference grid and common bonding network, the bonded equipotential plane in a data center
SRG / mesh-BN: Signal reference grid, the grid of copper conductors giving a low-impedance reference across a broad frequency range
SRI: Solar Reflectance Index, combining SR and TE into one number per ASTM E1980, with black at 0 and white at 100
SRI / cool roof: Solar reflectance index, the combined reflectance and emittance rating used by energy codes and rebate programs for reflective roofs [https://anvilfield.com/field-guides/glossary/sri-cool-roof/]
SRL: Self-retracting lifeline, a connector that locks quickly to shorten free fall
SRW: Segmental retaining wall, a mortarless wall of stacked dry-cast concrete units
SSD: Saturated surface dry, the aggregate moisture baseline used to correct batch water for free or absorbed moisture [https://anvilfield.com/field-guides/glossary/ssd/]
SSSP: Site-specific safety plan, your program written for one project; commonly required by the GC
ST / OT / DT: Straight time, overtime at one and a half, and double time at two times the regular rate
STA: Seal of Testing Assurance, the US Composting Council program certifying compost maturity and quality
Stab: The connector that joins a bucket to the section's vertical bus
Stabilization: Putting a temporary or permanent cover back on disturbed soil so it stops eroding, on a permit deadline once work stops
Stabilizer: The agent mixed into an FDR base, chemical (cement, lime) or bituminous (emulsion, foamed asphalt), that gives it strength
Stabilizer / ladder bracket: A top attachment that holds the ladder off the gutter and widens its contact against the wall
Stack: A vertical drainage or vent pipe carrying through one or more floors
Stack effect: Warm air rising and leaking out the top of a building, pulling cold air in at the bottom [https://anvilfield.com/field-guides/glossary/stack-effect/]
Stack re-entrainment: The exhaust plume coming back into the building through an intake because the stack failed to disperse it
Stack temperature: Flue gas temperature; high stack points to a fouled exchanger or excess air, and every 50 degrees F costs about 1 percent efficiency [https://anvilfield.com/field-guides/glossary/stack-temperature/]
Stack vent vs vent stack: The stack vent is the dry top of a soil stack carried to the roof; the vent stack is a separate vent running alongside it
Stacking: Two or more trades working in the same physical space at the same time, often one over the other
Stage-storage: The relationship between water depth in the basin and the volume it holds at that depth, set by the grades you build
Staging: Matching the number of running chillers and pumps to the load, adding the next only when needed [https://anvilfield.com/field-guides/glossary/staging/]
Stainless / hot-dip fastener: Type 304 or 316 stainless, or hot-dip galvanized nails, the only metals that resist cedar tannin corrosion; never electro-galvanized
Stakeless / clamp-on: A loop ground test that needs no pins or disconnect but requires a parallel return path
Staking: Temporary support using short upright stakes and ties to steady a small new tree
Stall: A single parking space, commonly 9 ft by 18 ft, with the minimum set by the local zoning code
Stamped concrete: Poured concrete colored and imprinted while plastic to mimic stone, brick, wood, or tile, then sealed
Standard air: Reference density of about 0.075 lb per cubic foot at sea level and 70 degree F
Standard count: A daily reference reading that confirms a nuclear gauge has not drifted before it is used
Standard hook: A code-defined bend and tail that anchors a bar where straight development length is short
Standard hook / ldh: A code-defined 90, 135, or 180 degree bend that anchors a bar in less length, with its own development ldh
Standard mileage rate: An IRS per-mile method for deducting vehicle use, as an alternative to actual expense
Standard Proctor (ASTM D698): The lower-energy compaction test, lighter rammer and shorter drop
Standard-cured: Cylinders given the controlled initial cure and lab moist curing, used for ACI 318 acceptance of the concrete
Standby / offline / VFD: Load runs on utility, transfers to the inverter on failure with a brief break
Standby loss: Heat a stored tank sheds to the room around the clock, whether or not anyone draws water
Standby power: A source rated to run only on a normal-supply failure, limited hours at a varying load
Standby rating: The generator output rated for emergency-duty use during a utility outage, above the prime and continuous ratings
Standing pressure test: Holding nitrogen pressure and watching the gauge over time, with temperature correction, to prove tightness [https://anvilfield.com/field-guides/glossary/standing-pressure-test/]
Standing seam: A concealed-fastener panel with a raised, interlocking seam above the water line; the panel floats on clips [https://anvilfield.com/field-guides/glossary/standing-seam/]
Standoff / L-foot: The attachment on a penetrating mount that lifts the rail off the roof above the flashing
Standpipe: A vertical trapped and vented pipe a washer discharges into through an air break, with the opening height set by code [https://anvilfield.com/field-guides/glossary/standpipe/]
Standpipe class I / II / III: Classification by user: fire department 2.5 in, occupant 1.5 in, or both at one station
Starter course: The first sealed course at the eaves and rakes that locks the bottom edge and backs the field cutouts
Starter fertilizer: A phosphorus-forward blend applied at install to drive root development
Starting torque: Breakaway or locked-rotor torque, the torque made at the instant of starting
Statement of Compliance: The signed certification, made under penalty of perjury, that the payroll is accurate and the wages were paid
Statement of special inspections: The permit document listing every special inspection and test, who performs it, and whether it is continuous or periodic
Static bypass: Automatic solid-state switch to raw utility on UPS overload or fault
Static cable: EHS steel cable on drilled hardware that rigidly limits movement between leaders
Static deflection: How far the isolator compresses under load; sets the natural frequency and the isolation
Static head: The pressure to lift water, about 0.43 psi per foot of elevation, or 1 psi per 2.31 ft [https://anvilfield.com/field-guides/glossary/static-head/]
Static head (ds): Water depth up to the overflow inlet with the primary assumed blocked
Static lift: The vertical rise from the pump-off water level to the high point of the discharge
Static load rating: The code-required load a carrier is tested to hold at the fixture, commonly 250 to 500 lb and up to 1000 lb for heavy-duty units
Static load test: A direct load applied to the pile with settlement measured, the benchmark capacity test under ASTM D1143
Static pressure: The pressure in the system with no water flowing, the highest pressure the system sees, peaking overnight when demand drops [https://anvilfield.com/field-guides/glossary/static-pressure/]
Static pressure (ESP): External static pressure across the unit in inches of water column, the airflow-restriction indicator [https://anvilfield.com/field-guides/glossary/static-pressure-esp/]
Static pressure reset: Trim-and-respond logic that lowers the duct pressure setpoint to the minimum that still serves the hungriest zone [https://anvilfield.com/field-guides/glossary/static-pressure-reset/]
Static transfer switch: The device that moves a dual-corded load between sources fast enough that the equipment does not see a break
Static twin: A 3D model or scan with no live data, a record rather than a true twin
Static vs dynamic load: Weight a cabinet holds at rest versus while rolling on its casters, the lower number
Static vs working pressure: Static is pressure with no flow; working (dynamic) is pressure while water flows, and is what you design to
Static water level: Where water stands in the casing with the pump off
Static-dissipative flooring: Reads above 1.0 x 10^6 up to below 1.0 x 10^9 ohms; drains charge in a controlled, slower way
Station / program: A station is one valve and its heads; a program is the zones, days, and start time that run as a group
Stay-in-place (SIP) forms: Permanent corrugated galvanized metal deck forms left in the structure after the pour, versus removable plywood forms
STC: Sound Transmission Class, how well a wall assembly blocks airborne sound between rooms
Steam trap: An automatic valve on two-pipe systems that passes condensate and air but holds live steam [https://anvilfield.com/field-guides/glossary/steam-trap/]
Steel erection: The field process of picking, setting, connecting, and plumbing steel members into a frame, regulated under OSHA 1926 Subpart R
Steep-slope: A roof that sheds water with overlapping materials, commonly above roughly 3:12 to 4:12
Stem wall: The foundation wall on the footing that lifts the structure out of the ground
Step flashing: One bent metal piece per course at a sidewall, woven into the shingles, never a single caulked strip [https://anvilfield.com/field-guides/glossary/step-flashing/]
Step load: A block of load applied at once, the transient that often governs the size [https://anvilfield.com/field-guides/glossary/step-load/]
Step potential: The voltage difference between your feet in the energized ground around a downed line, which drives current through the body
STF: Slips, trips, and falls, the grouped category for same-level loss-of-footing injuries
Stick-built vs unitized: Stick is field-assembled mullion by mullion; unitized is factory-glazed panels craned in and interlocked.
STO: Safe torque off, a hardwired function that removes motor torque without removing drive power, not a lockout
Stone column / aggregate pier: A stiff vertical column of compacted stone that reinforces soft soil; aggregate piers are rammed for higher stiffness, stone columns also drain
Stone reservoir: The clean open-graded stone layer under the surface that stores water in its voids and spreads load [https://anvilfield.com/field-guides/glossary/stone-reservoir/]
Stone-coated steel: A steel panel surfaced with bonded stone granules to mimic tile, shake, or shingle
Stop-work authority: Every worker's explicit right to stop unsafe work with no blame for the call [https://anvilfield.com/field-guides/glossary/stop-work-authority/]
Storage tank: A heater that keeps a tank of water hot and ready, sized by volume plus recovery
Storage tier: A layer of storage at a given speed and cost, holding data that matches how it is being used right now
Stored materials: Material delivered but not installed, billable with invoice, photo, insurance, and storage proof
Stored-pressure extinguisher: A unit holding agent and propellant in one cylinder; the gauge shows its charge
Storefront vs window wall: Storefront is the lighter ground-floor system with doors; window wall sits between floors on the slab, while curtain wall hangs past the slab.
Storm collar: An umbrella-shaped counterflashing over a pipe boot's top band that sheds water off the clamp
Storm restoration: Assessing and documenting storm damage, helping the homeowner work the claim, and replacing the roof to the approved scope
Stormwater retention: Rainfall the media, drainage layer, and plants hold and release slowly or use, the function many green roofs are credited for
Story pole: A marked stick laid out to the coursing so every lead is built to the same course heights
Straight pull: Conductors enter one wall and exit the opposite wall in line, sized at 8x the largest raceway
Strainer cycle: Direct free cooling routing tower water straight into the chilled-water loop through a filter, most efficient but fouling-prone
Strand / lashing: The steel messenger that carries aerial load, and the wire that lashes the fiber cable to it
Stranded capacity: Power, cooling, or space built and paid for but unusable because another resource or limit caps it first [https://anvilfield.com/field-guides/glossary/stranded-capacity/]
Stranded energy: Charge left in damaged cells after a fire that can drive reignition hours later
Stratification efficiency: The fraction of the tank volume that is usable cooling rather than dead thermocline and end zones
Stray-current interference: CP current picked up by a foreign structure that corrodes where the current discharges back to the soil; managed with bonds
Streaming telemetry: The device pushing structured counters and stats continuously at sub-second rates, commonly over gNMI/gRPC, versus SNMP polling
Strength test: The average of the cylinders in one set, broken at the designated age [https://anvilfield.com/field-guides/glossary/strength-test/]
Strength-maturity calibration: The mix-specific curve of strength against maturity, built per ASTM C1074
Stress cone: The geometric or stress-relief device that spreads the field at the shield cutback so the insulation is not overstressed [https://anvilfield.com/field-guides/glossary/stress-cone/]
Stress control: The part of a termination that grades the concentrated field at the shield cutback so it does not track and fail
Stress plate: The round metal plate under a fastener that spreads the load into the membrane
String / array: Modules in series make a string; strings together make the array
Stringer: The horizontal member tying pedestal heads into a grid for lateral stability; bolted or snap-on, often gasketed for the air seal [https://anvilfield.com/field-guides/glossary/stringer/]
Stringerless / cornerlock: An understructure with no stringers, locating panels on the pedestal heads and corners, with less lateral capacity
Strip footing: A continuous footing under a wall that spreads a line load; also a wall or continuous footing
Stripe coat: A brushed coat on edges, welds, and bolts before spraying, where the coating otherwise pulls thin
Stripping: Loss of bond between binder and aggregate from trapped moisture, the main WMA risk
Struck-by: Worker hit by a flying, falling, swinging, or rolling object or vehicle
Struck-by / Focus Four: A worker hit by a moving or falling object: a vehicle, equipment, a swinging load, or a dropped object. One of OSHA's four construction hazard groups, the Focus Four, also called the Fatal Four.
Structural / full demolition: Taking the whole structure down, frame and all, to clear the site.
Structural base: The asphalt or concrete pavement under the surface that controls flatness, drainage, and life
Structural fill: Fill placed and compacted to a tested density to carry a structure or pavement without settling
Structural fireproofing: Insulation applied to structural steel so it stays below its failure temperature in a fire and keeps carrying load for the rated time
Structural number (SN): The total structural strength AASHTO 93 says the section needs over the subgrade; not a thickness
Structural silicone glazing (SSG): Glass bonded to the frame with structural silicone that carries the wind load, with no exterior cap; four-side SSG bonds all edges.
Structural vs architectural: Structural panels span open framing; architectural panels need a solid deck and a steeper slope
Structured cabling / TIA-606: A fixed, tested, labeled patch field, and the administration standard that names every cable, port, and space
Structured vs unstructured task: A structured task is repetitive and predictable enough for a robot to follow; an unstructured task is custom or unpredictable and needs a person
STS: Static transfer switch, which moves load between two sources fast enough to avoid an interruption [https://anvilfield.com/field-guides/glossary/sts/]
Stub: A 90-degree bend that stands a leg up to a box or gear, set from the take-up
Stub-out: The capped end of a supply or drain pipe roughed to the fixture, where the stop or trap connects at finish
Stub-up: The rebar tail or bonded conductor brought up out of the footing before the pour to keep the connection accessible
Sub-fascia: A rough backing board straightened to a line, with the finish fascia run over it
Sub-floor heat: A glycol grid, electric heat trace, or ventilated void under the slab insulation that keeps the subgrade above freezing.
Sub-slab depressurization (SSD): A fan-driven system that holds the soil under the slab at lower pressure than the building so gas vents outside
Subbase: Compacted granular layer for uniform support, drainage, and a capillary break, not for strength
Subcontractor default insurance: A two-party insurance policy, often called SubGuard, by which a GC insures against sub default instead of requiring bonds, carrying a deductible and the prequalification duty
Subcooling: Saturation temperature at liquid pressure minus the liquid line temperature; liquid cooled below its condensing point [https://anvilfield.com/field-guides/glossary/subcooling/]
Subcooling / superheat: The charge-verification readings: subcooling for a TXV unit, superheat for a fixed-orifice unit [https://anvilfield.com/field-guides/glossary/subcooling-superheat/]
Subfloor prep: Making the slab sound, clean, flat, dry, and profiled per ASTM F710 before flooring
Subgrade: The natural soil at the bottom of the section that carries the base and pavement above it [https://anvilfield.com/field-guides/glossary/subgrade/]
Subgrade pumping: Saturated fines forced up into the aggregate voids under repeated load, contaminating and weakening the base.
Submersible pump: A sealed motor-and-pump unit set down in the water that pushes water up the drop pipe, sized to gpm and total dynamic head
Submeter: A meter measuring a tenant or load below the utility's revenue meter, owned by the building, not the utility
Submittal: Product data, shop drawing, sample, or mockup sent to prove an item meets the spec before it is ordered or fabricated
Submittal register: The master list of required submittals by spec section, tied to review status and procurement lead time
Substantial completion: The milestone where the owner can occupy and use the building for its intended purpose; commonly starts the warranty clock [https://anvilfield.com/field-guides/glossary/substantial-completion/]
Substation: The installation that ties the site to the grid and steps high voltage down to medium voltage
Substrate deflection (L/360): Allowable bending of the floor framing under load, the clear span divided by 360 for ceramic and porcelain, 720 for natural stone.
Succession planning: The multi-year work of building a transferable business and choosing and carrying out how the owner exits
Suction and discharge gauges: Pressure gauges across the pump that read the head it is making, locating the operating point on the curve
Suction diffuser: A pump-inlet fitting combining a flow straightener, a strainer, and a support leg to steady flow and screen debris
Suction lift: Vertical distance from the water surface up to a pump mounted above it, practically limited to roughly 20 to 25 ft [https://anvilfield.com/field-guides/glossary/suction-lift/]
Suction riser: A vertical suction line the gas must drag oil up, the hardest spot for oil return
Suicide cord: A cord with a male plug on both ends, used to backfeed a house, with live exposed prongs; illegal and deadly
Sum of diameters: The single-conductor fill basis where large conductors lie in one layer and their diameters total no more than the tray width
Sump: A recessed tapered area at a drain or scupper that drops the membrane so water reaches the bowl
Supercapacitor: Electrostatic storage delivering very high power for seconds with very long cycle life and little energy
Superflat: Very flat floor for defined-traffic narrow-aisle use, measured in the wheel paths
Superheat: Degrees the suction vapor sits above its saturation temperature at the current pressure; what a TXV or EEV controls [https://anvilfield.com/field-guides/glossary/superheat/]
Superheat / subcooling: Charge-check measurements in degrees; superheat for fixed-orifice, subcooling for expansion-valve systems [https://anvilfield.com/field-guides/glossary/superheat-subcooling/]
Superpave: Superior Performing Asphalt Pavements, the AASHTO mix design system from the SHRP program
Superseded sheet: An old revision replaced by a newer one, pulled from the build and marked VOID but kept in the archive
Supervisory vs alarm: A condition that impairs protection, like a closed valve, versus a confirmed fire condition like waterflow
Supplement: A documented request to add real missed or code-required scope to the carrier's estimate, with proof
Supplemental support system: Hardware that adds support or limits movement of a tree part, never primary support for the whole tree
Supply air temperature (SAT): Temperature of the air leaving the AHU, commonly around 55°F in a VAV system, subject to reset
Supply fixture unit (WSFU): A load value for a fixture's water demand, used to total the load and pick the arrestor size
Supply static: Positive pressure read after the blower and coil, before the first takeoff or accessory
Supply water temperature: The temperature of the water sent to the loops, commonly 90 to 120°F for radiant, set by the design
Supported scaffold: A platform held up from below by legs, frames, or poles bearing on a firm foundation
Surcharge: A load near the edge, such as spoil or equipment, that pushes the trench wall toward failure [https://anvilfield.com/field-guides/glossary/surcharge/]
Surety: The party that issues a bond and that you repay if it pays a claim
Surety bond vs insurance: A three-party guarantee, not a two-party insurance policy; the surety expects no losses and you repay any claim
Surface / wearing course: The top lift the tires ride on; fine, dense, watertight, skid-resistant
Surface cleaner: A shrouded spinning bar for flatwork that cleans evenly and fast without the zebra striping a wand leaves
Surface infiltration test: ASTM C1701 or C1781 ring test of how fast the finished surface takes water, the acceptance measure
Surface port: A fitting glued over the crack to inject resin, spaced roughly to the wall thickness
Surface prep (SP1/SP6/SP10/SP5): SSPC/NACE cleanliness standards: solvent clean, commercial blast, near-white blast, and white metal blast
Surface profile (CSP): The ICRI concrete surface profile, 1 smooth to 9 very rough, the texture the prep must reach for bond
Surface thickness: Total built depth of the surface, commonly 13 mm, that sets the shock absorption
Surfactant: An additive that breaks the water's surface tension so the solution clings and sheets instead of running off
Surge: A momentary reversal of refrigerant flow through the compressor when the lift exceeds what the impeller can make at that flow, repeating until conditions change [https://anvilfield.com/field-guides/glossary/surge/]
Surge line: The low-flow, high-head boundary on the compressor map; cross it and the machine surges
Survivability: The protection that keeps an emergency circuit working under the conditions of the emergency, to the level NFPA 72 requires
Survivability / 2-hour pathway: The requirement that the public-safety system keep working in a fire, built from fire-rated cable and listed enclosures
Suspended / ACT ceiling: A metal grid hung from the structure on wires with acoustic tiles dropped in, hiding the plenum and keeping it accessible
Suspended scaffold / swing stage: A work platform hung from a building's roof on wire ropes to reach a facade; the two-point version is the swing stage
Suspension trauma: Orthostatic intolerance from hanging motionless in a harness; why prompt rescue is planned [https://anvilfield.com/field-guides/glossary/suspension-trauma/]
Suspension wire rope / secondary brake: The rope that carries the platform load, and the automatic brake or pawl that grabs if the hoist overspeeds
SVB / SPVB: Spill-resistant vacuum breaker; a PVB built not to spill, so it can be installed indoors (ASSE 1056) [https://anvilfield.com/field-guides/glossary/svb-spvb/]
Swale: A shallow, usually vegetated graded channel that collects sheet flow and carries it to an outlet at a 1 to 2 percent flow line
SWBP (lb/ft): Sidewall bearing pressure, tension out of a bend divided by the bend radius in feet
Swing fall: The pendulum motion when the anchor is off to the side rather than overhead
Swing radius: The arc a boom or counterweight sweeps through as equipment rotates, kept barricaded [https://anvilfield.com/field-guides/glossary/swing-radius/]
Switched: A strip whose outlets can be turned on and off remotely over the network
SWPPP: Stormwater pollution prevention plan, the site-specific written plan and map of the BMPs, inspections, and responsible party
Symmetrical RMS: The fault current measured as a sine wave centered on zero, the base value the study reports
Synchronization: Matching an incoming set's voltage, frequency, phase angle, and rotation to the bus before its breaker closes
Synchronized swing: Many GPUs ramping power together on the same training step, so the peaks add instead of scattering
Synchronizing: Matching voltage, frequency, phase sequence, and phase angle before closing a breaker to the bus
Synchronous / asynchronous: Replication that confirms at both sites for zero RPO at short range, versus trailing copy for any distance
Synchroscope / sync-check (25): The instrument showing phase relationship and the relay (ANSI 25) that supervises and permits the close
System bonding jumper (SBJ): The neutral-to-ground connection made at a separately derived source such as a 4-pole generator, the counterpart to the service main bonding jumper
System curve: The plot of head the piping demands against flow; it climbs with the square of velocity because friction rises with velocity [https://anvilfield.com/field-guides/glossary/system-curve/]
System effect: Performance lost when inlet or outlet conditions differ from the fan's rating basis
System resistance (STM97.1): Resistance of person plus footwear plus floor in series, commonly held below 1.0 x 10^9 ohms
System volume: The total water in the boiler, piping, coils, and terminals; the input most often guessed too low
System warranty: Manufacturer coverage for the whole assembly including installation, requiring a certified installer
Systems manual: The operations-facing rollup tying the as-builts, sequences, as-left settings, O&M, and training into one operable reference [https://anvilfield.com/field-guides/glossary/systems-manual/]
T: Thickness or depth in feet, converted from inches before the calculation (4 in = 0.333 ft)
T and M / force account: Cost-plus work tracked by men, hours, equipment, and material on a signed ticket the daily must back
T and P relief: Temperature-and-pressure relief valve, the safety valve on a water heater or hot-water vessel
T&M: Time and material; out-of-scope work billed on documented labor, equipment, and material rather than a fixed price, and flagged before it is performed
T&P valve: The temperature and pressure relief valve on the heater, a safety device relieving at 150 psi or 210 degrees F, never the expansion fix [https://anvilfield.com/field-guides/glossary/t-p-valve/]
T-code: The maximum surface temperature class of equipment (T1 450 C to T6 85 C), which must stay below the material's autoignition temperature
T-joint: The three-layer point where two seams cross, the highest-risk spot on a field seam
T-rating: Time before the unexposed side rises ~325 degrees F (181 degrees C); governs floor penetrations and combustibles against the far side
t/NMAS: Lift-thickness-to-NMAS ratio; a minimum near 3 (fine) to 4 (coarse) sets the thinnest lift that will compact [https://anvilfield.com/field-guides/glossary/t-nmas/]
T1, T2, T3: Standard three-lead motor terminal markings that receive L1, L2, L3
T50: Time in seconds for the patty to reach a 20 in spread, an estimate of plastic viscosity
t_OA: Outdoor air dry-bulb temperature entering the device, the cold side in winter
t_RA: Return or exhaust air dry-bulb temperature entering the device from the building
t_SA: Supply air dry-bulb temperature leaving the device toward the building or DOAS coil
Ta: Air temperature in degrees Celsius, measured in the shade at the slab
TAB: Testing, adjusting, and balancing: measuring an air system, adjusting it, and setting it to design, then reporting it [https://anvilfield.com/field-guides/glossary/tab/]
Table 1: The list in 1926.1153 pairing common tasks with specified water or vacuum controls; followed fully, it exempts you from air monitoring
Table 1 / Table 4 / Table 5: Chapter 9 tables for the percent fill, the conduit dimensions and allowable areas, and the conductor areas
Tabulated data: The manufacturer's depth ratings and limits for a shield or shoring system [https://anvilfield.com/field-guides/glossary/tabulated-data/]
TAC: Template-assisted crystallization, a salt-free conditioner that alters scale but removes no hardness
Tack coat: A light asphalt-emulsion spray that bonds the new overlay to the existing surface so the layers act as one [https://anvilfield.com/field-guides/glossary/tack-coat/]
Tack coat / residual rate: The emulsion bond between old and new, measured by the asphalt left after it breaks, in gal/sy
Tackifier: Binder that glues the mulch and seed down and lubricates the pump
Tailgating / piggybacking: Following an authorized person through a door, with or without their help
Take-up / deduct: The length a 90 consumes, subtracted from the stub height to find the mark, stamped on the bender
Take-up tension: The device, screw or gravity counterweight, that holds belt tension as the belt stretches and the load changes
Takeoff: The count of fixtures and measure of pipe, fittings, and equipment from the plans [https://anvilfield.com/field-guides/glossary/takeoff/]
Takt: A fixed production beat at which trades flow through zones like a train, each finishing its zone and handing off on the same interval
Tan-delta: Dissipation factor, the share of applied voltage lost as heat in the insulation, a diagnostic of overall insulation condition
Tank lining vs exterior coating: The interior immersion film in contact with the product, versus the exterior coating that fights corrosion and UV
Tankless / on-demand: A heater that makes hot water as it flows, sized by flow at the rise, with no stored mass
Tap conductor: A conductor connected to a feeder with no overcurrent device at the connection point, smaller than the feeder device protects at its ampacity
Tapered insulation: Insulation board manufactured at an angle to build drainage slope into a flat structural deck [https://anvilfield.com/field-guides/glossary/tapered-insulation/]
Tapered vs butt joint: A tapered joint meets factory long edges in a recess that finishes flush; a butt joint meets cut ends with no recess and finishes proud, so it is harder to hide
Tapping saddle / sleeve: A saddle clamps the corp to the main for small taps; a tapping sleeve and valve carries a wet tap larger than about 2 in on a live main
Tare: The empty reel's weight, stamped on the flange, subtracted to get net conductor weight
Target: Anything the tree could hit if it fails: people, structures, vehicles, roads, utilities; occupancy sets how often it is present
Tarp battens / furring strips: Wood strips, commonly 2x4 or 1x4, that wrap and sandwich the tarp edges and are fastened into sound decking to anchor against wind
Task tuning / trim: High-end trim caps the maximum for savings; low-end trim raises the minimum above the flicker floor
TBB: Telecommunications bonding backbone, the conductor from the PBB to the SBBs, sized by length, minimum 6 AWG
Tc: Concrete surface temperature in degrees Celsius, measured per ASTM C1064, not the air temperature
TC bolt: Twist-off tension-control bolt, F1852 or F2280, whose spline shears at tension
TCC: Time-current curve, the log-log plot of device operating time versus current
TCC (time-current curve): The log-log plot of tripping time against fault current; the coordination study plots every device in a path on one chart
TCDD / TCCF / TCOS: Uptime certification of design documents, constructed facility, and operational sustainability
TCO: Total cost of ownership: amortized capex plus operating cost over the asset life, usually expressed per MW
TCS: Technology cooling system, the clean conditioned secondary loop from the CDU to the cold plates, held to the strict chemistry [https://anvilfield.com/field-guides/glossary/tcs/]
TDD: Tubular daylighting device, or solar tube, a roof dome feeding a reflective tube to a ceiling diffuser [https://anvilfield.com/field-guides/glossary/tdd/]
TDH: Total dynamic head, the static lift plus friction head the pump must overcome, in feet
TDP: Thermal design power, the watts a chip is rated to dissipate, which the cooling has to remove [https://anvilfield.com/field-guides/glossary/tdp/]
TDR: Time-domain reflectometer, sends a low-voltage pulse and times the reflection
TDS: Total dissolved solids in parts per million, the plain-language read on dissolved ion load [https://anvilfield.com/field-guides/glossary/tds/]
TDS / conductivity: Total dissolved solids, measured in the field as electrical conductivity, the live blowdown signal
Tear-off (replacement): Removing the roof to the structural deck and building a new assembly
Tee / wye: A branch connection; drainage uses a wye and eighth bend to enter flow, supply uses tees
TEFC / ODP: Totally enclosed fan-cooled and open drip-proof, the two common enclosures
Tegular vs lay-in edge: Tegular tile is rabbeted to drop below the grid for a reveal; lay-in tile sits flat on top of the grid flange
TEL: Total effective length, the longest supply run plus the longest return run, with each fitting counted as its equivalent length of straight duct
Telematics: GPS and sensor data on how a vehicle is driven, including speed, hard braking, cornering, and location, used for driver scoring
Temp power: Temporary power, the electrical system that runs a construction site before the permanent service is energized
Temperature clamp: A pipe-mounted thermistor or thermocouple; accuracy and insulation from ambient air decide the reading
Temperature coefficient (beta): How much Voc changes per degree of cell temperature, from the module datasheet
Temperature mapping: A color map of mat surface temperature from the infrared sensor, used to keep rolling in the window and find cold spots
Temperature rise: Supply minus return air temperature on heating, held inside the nameplate range [https://anvilfield.com/field-guides/glossary/temperature-rise/]
Temperature rise (ΔT): Setpoint minus cold inlet, in degrees F, taken on the coldest-month inlet
Temperature split / delta-T: Return-air temperature minus supply-air temperature across the coil, in °F
Tempered water: Blended hot water for hand washing, defined in the model code as 85 degrees F to 110 degrees F
Tempering: The one controlled addition of withheld water on site to reach the design slump
Temporary shoring: Engineered bracing or support for a structure that has lost capacity, designed and called for by a structural engineer
Tenant improvement (TI) / fit-out: The construction that turns a base-building shell into a finished space for a specific tenant
Tender zone: A temperature band where the mat is unstable under the roller and shoves or checks instead of compacting [https://anvilfield.com/field-guides/glossary/tender-zone/]
Tension anchor / tieback: A helical pier loaded in uplift, where the plates bear on the soil above them, used for guy anchors, solar tie-downs, and retaining-wall tiebacks.
Tension bar / band: The bar woven into the fabric end and the bands that clamp it to a terminal post
Terminal post: A corner, end, or pull post that the fabric tensions against, heavier than a line post
Termination: A connection joining a conductor to a device, lug, breaker, or busbar
Termination bar: A metal strip fastened through the membrane to hold the top of a base flashing, capped with sealant [https://anvilfield.com/field-guides/glossary/termination-bar/]
Termination rating: The temperature rating of the lug or terminal, which caps the conductor ampacity under 110.14(C) [https://anvilfield.com/field-guides/glossary/termination-rating/]
Terrazzo: A poured composite floor of decorative stone or glass chips set in a matrix, ground and polished to expose the chips
Terrestrial vs mobile / SLAM: Terrestrial is the high-accuracy tripod scanner, setup by setup; mobile / SLAM is the fast lower-accuracy walk-through that tracks its own motion
Tertiary treatment: Filtration and disinfection after primary and secondary treatment, the common reclaimed standard
TES: Thermal energy storage, a chilled water or ice tank that holds the cooling loop through the chiller restart [https://anvilfield.com/field-guides/glossary/tes/]
TESP: Total external static pressure, the supply-side static and return-side static added as magnitudes
Test ball / plug: An inflatable or mechanical plug that caps an opening to hold the test head or pressure
Test cock: A small numbered valve tapped into the assembly body that the gauge hoses connect to
Test cocks: The small ports on a backflow assembly, opened to drain and relieve it for winter and used to test it
Test panel: Shot sample cored for strength and consolidation, since a cast cylinder does not represent shotcrete
Test pressure: The raised pressure held during the test, commonly 1.5 times the design pressure for a hydrostatic test
Test pressure (P): The static the section is pressurized to for the test, in inches of water gauge
Tetany: Sustained muscle contraction from current, which can keep a victim from letting go of a conductor
Thatch: The layer of dead and living stems and roots between the blades and the soil, a problem over about 1/2 in
THD: Total harmonic distortion, the harmonic content on voltage or current as a percentage [https://anvilfield.com/field-guides/glossary/thd/]
The happy moment: The point right after the job when the customer has just seen the finished work and is most satisfied; the best time to ask for a review
The three capacities: Power, cooling, and space; the site runs out of whichever binds first
The three Cs: Character, capacity, and capital, the pillars a surety underwrites you on
Thermal / infrared survey: An inspection using a camera that maps surface temperature, revealing moisture, faults, and hot spots a visual camera cannot see.
Thermal / temperature segregation: Temperature difference across the mat as placed, leaving cold spots that compact poorly
Thermal backfill: Fluidized thermal backfill or thermal sand engineered to hold a low, stable RHO around the bank, replacing native spoil
Thermal break: A low-conductivity barrier (polyamide or poured-and-debridged resin) in the aluminum frame that cuts heat flow and stops the frame sweating.
Thermal bridge: A path, like a bare metal hanger, that shorts heat past the insulation and sweats or corrodes on cold service
Thermal bridging: Heat conducting around the insulation through framing, so the whole-assembly R falls below the cavity R
Thermal disinfection: Running the system hot to pasteurize it, a remediation step that has to account for scald risk
Thermal drift: A pressure change on a long hold caused by the test water warming or cooling, read against the temperature log so it is not mistaken for a leak [https://anvilfield.com/field-guides/glossary/thermal-drift/]
Thermal emittance (TE / emissivity): How well a surface re-radiates absorbed heat, on a 0 to 1 scale; higher sheds heat faster
Thermal envelope: The temperature and humidity range allowed at the IT equipment intake, per ASHRAE TC 9.9 [https://anvilfield.com/field-guides/glossary/thermal-envelope/]
Thermal expansion: The volume increase of water as it is heated, on the order of 1.5 to 2 percent over a residential temperature rise
Thermal expansion / flexibility: The growth of pipe when heated, and the routing flexibility and supports that absorb it within allowable stress
Thermal expansion / loose nailing: Vinyl's large movement with temperature; the panel must hang from a centered, loose nail so it floats and does not buckle
Thermal fog / hydroxyl / ozone: Deodorization tools; fog penetrates like smoke, hydroxyl is occupied-safe, ozone runs unoccupied only
Thermal fogging: A heated deodorizing fog that penetrates the paths the smoke took to reach residual odor
Thermal profile: A foot-by-foot temperature map of the mat, usually from an infrared bar on the paver
Thermal ride-through: The time a load has between losing cooling and crossing its temperature limit, seconds on a dense liquid rack
Thermal runaway: A self-sustaining, self-heating cell failure that vents flammable gas, propagates cell to cell, and resists conventional suppression [https://anvilfield.com/field-guides/glossary/thermal-runaway/]
Thermal segregation: Cold lumps or streaks in the mat from uneven load temperature, a low-density defect a material transfer vehicle prevents
Thermal-stress cracking: A pane cracking from a temperature difference between its hot center and cooler framed edge, the main film-related break risk
Thermally neutral: A rack whose rear door captures nearly all its heat, so its exhaust leaves near room temperature
Thermocline: The thin transition layer between the cold stored water and the warm return
Thermographer level: ASNT SNT-TC-1A qualification tiers, Level I to scan, Level II to interpret and judge severity, Level III to write procedures
Thermographer qualification: Recognized training and certification in infrared interpretation, commonly Level I and Level II under ASNT SNT-TC-1A.
Thermography (IR scan): Infrared survey under load that finds a loose joint by its heat before it fails
Thermography / IV-curve: IR imaging that finds hot spots and dead modules and strings, and current-voltage tracing that confirms module or string health electrically
Thermoplastic: A molten marking material applied around 90 to 125 mils that outlasts paint on high-traffic markings [https://anvilfield.com/field-guides/glossary/thermoplastic/]
Thermoplastic / thermoset: Thermoplastic re-melts with heat so seams weld; thermoset is cured and does not re-melt, so seams are taped
Thermoset: A cured material that does not re-melt with heat, so EPDM seams are taped and primed, not welded
Thermostatic element: The wax or bimetal sensor that expands and contracts with mixed-water temperature to move the valve piston
theta: The deflection angle of the bend, 90, 45, 22.5, or 11.25 degrees for standard fittings [https://anvilfield.com/field-guides/glossary/theta/]
THHN: Thermoplastic, high heat to 90C, nylon jacket, dry locations; usually sold dual-rated as THHN/THWN-2
Thickened edge: The slab run deeper along an edge or load line to carry the higher bending a wheel puts on an edge [https://anvilfield.com/field-guides/glossary/thickened-edge/]
Thickener: The structure that holds the base oil, such as lithium, lithium-complex, or polyurea; mixing incompatible types fails the grease
Thickness / DFT: The applied depth that delivers the rating; dry film thickness is the intumescent equivalent
Thin / ultra-thin overlay: A new HMA wearing course about 1 to 1.5 in or less, a functional surface treatment that adds little structure
Thinset mortar / coverage: The cement mortar bonding tile to the substrate; coverage is the share of the tile back in contact with mortar, commonly 80 percent dry and 95 percent wet.
Three points of contact: Two hands and one foot, or two feet and one hand, on the ladder at all times while climbing
Three-coat / lath: Scratch, brown, and finish coats keyed into metal lath over the WRB
Three-phase inspection: The preparatory, initial, and follow-up control model from the US Army Corps of Engineers
Three-sided adhesion: Sealant bonded to both walls and the bottom, which cannot stretch and tears when the joint opens
Three-way match: Checking the PO, the receiving record, and the invoice against each other before paying [https://anvilfield.com/field-guides/glossary/three-way-match/]
Three-way valve: A diverting coil valve that bypasses water around the coil, a direct cause of low delta-T
Throttling valve: A valve built to regulate flow at intermediate positions, such as a globe
Through vs membrane penetration: Through breaches both sides of the assembly; membrane breaches one side; each has its own tested system
Through-bolt cleat board-up: Securing method with plywood outside and 2x4 cleats inside, clamped together by carriage bolts through the opening, used where security matters or no frame remains
Through-fastened vs standing seam: Screw-down panels fastened through the face into the secondary, versus concealed-clip panels with the seam locked above the water line
Through-hardware: An eye bolt or amon eye run fully through the stem and held with a washer and nut, bearing across the wood
Through-penetration: A breach through both sides of a rated wall or floor for a pipe or other item
Through-wall flashing: A continuous waterproof layer built across a masonry wall that catches interior water and discharges it at weeps [https://anvilfield.com/field-guides/glossary/through-wall-flashing/]
Throw: How far a unit heater pushes its warm air before it loses velocity, set by the fan and the louvers
Throw (T50): Distance from the device to where the supply jet decays to a terminal velocity, commonly 50 fpm
Throw / projection: Distance the stream stays coherent; it must meet or beat the door height
Throw-and-roll / throw-and-go: Fast temporary patch: cold mix dumped in and compacted, no cleaning or cutting
Thrust: The unbalanced outward force a pressurized pipe pushes at a bend, tee, cap, or reducer
Thrust block: A concrete mass that bears the thrust into undisturbed soil behind the fitting
Thrust restraint: Spring restraint that takes a fan's air thrust while still isolating vertically
Thumper: Surge generator that discharges into the fault to make an audible thump
THWN / THWN-2: Thermoplastic, wet rated, nylon; THWN is 75C wet, THWN-2 is 90C wet and dry
THWN-2 / THHN: Wet-rated building wire, and dry/damp-only building wire
TI allowance: The landlord's capped contribution to the fit-out, stated in dollars per square foot, usually paid as a reimbursement
TIA-222 loading analysis: The engineer's calculation under TIA-222 of whether a tower can carry specific equipment under code wind and ice loads
TIA-606: The administration standard for labeling and records, requiring an identifier at each cable end
Tie bar: Deformed bar across a longitudinal joint that holds lanes together and does not transfer load
Tieback / ground anchor: A drilled, grouted, post-tensioned tendon anchored in soil or rock behind the wall to hold it without bracing inside the hole.
Tier (I to IV): Uptime Institute infrastructure level, certified by Uptime, scoped to power and cooling
Tier 1 / Tier 2: OLTS insertion-loss certification versus OTDR event-by-event trace
Tier 4 Final: The EPA's most stringent engine emissions tier, typically requiring SCR and a DPF on large engines
Tiered plan: A good-better-best ladder of two or three plans at rising price and inclusion, matching price to what each customer will pay
Tile open area: The fraction of a perforated tile that passes air; commonly 25 percent, up to 50 to 60 percent for grilles [https://anvilfield.com/field-guides/glossary/tile-open-area/]
Tile profile: The shape of the tile, flat, low, or high (S-tile, barrel, mission), interlocking or overlapping, which sets the look and the water channel
Tilt-up: Wall construction where panels are cast flat on the floor slab and lifted upright by crane into place
Time and materials (T&M): Pricing by actual labor, material, and equipment against agreed rates, used when scope cannot be taken off in advance
Time to hire: Days from a seat opening to the new hire's start date; long times signal a dry pipeline
Time to productive: How long until a new hire runs profitable work solo; the real cost of a hire
Time-lapse: A camera and clip built to compress long stretches of progress into a short dated record
Time-related cost: A general condition that runs by the month for the job's duration, priced as monthly rate times months
Time-temperature defrost: Older control that defrosts on a fixed run-time interval once the coil is confirmed cold
Time-to-power: Elapsed time until a site can be energized; carrying cost accrues until it earns
TMGB / TBB: Telecom main grounding busbar and bonding backbone, the telecom grounding subsystem
TMV: Thermostatic mixing valve, which blends hot and cold to hold a set outlet temperature
TOC: Total organic carbon, the organics measure that resistivity is blind to, usually in parts per billion
Toe drain: The perforated pipe at the base of the drainage stone, sloped to a daylight outlet, that carries water off the back of the wall [https://anvilfield.com/field-guides/glossary/toe-drain/]
Toilet rough-in: The distance from the finished wall to the center of the closet flange, commonly 12 in, with 10 in and 14 in alternates
Tolerance: The allowed deviation of the built work from its true location, set by the spec and the trade standard, not by the instrument
Tolerance (+/- 10%): The acceptable band around design airflow, commonly plus or minus 10 percent at outlets, set by the spec
Tolerance zone: The hand-dig band on each side of a mark, commonly 18 to 24 in but set by state law
Ton: 12,000 BTU per hour of cooling, the unit of plant and chiller capacity [https://anvilfield.com/field-guides/glossary/ton/]
Ton / kW per ton: One ton equals 12,000 BTU per hour of cooling; kW per ton is chiller input power per ton, lower is more efficient
Ton of cooling: About 3.517 kW or 12,000 BTU per hour of heat rejection
Ton of refrigeration: 12,000 BTU per hour of cooling, about 3.516 kW, the heat to melt a ton of ice in a day [https://anvilfield.com/field-guides/glossary/ton-of-refrigeration/]
Ton-hour: 12,000 BTU of cooling, one ton of refrigeration delivered for one hour
tons = gpm x delta-T / 24: The US-unit heat balance tying cooling capacity to flow and temperature difference
Toolbox talk: A short crew safety briefing, often 5 to 15 minutes, on a relevant hazard; also called a tailgate talk or pre-job briefing [https://anvilfield.com/field-guides/glossary/toolbox-talk/]
Top-bar effect: Reduced bond for horizontal bars with a deep layer of concrete cast below them, penalized with a top-bar factor
Top-dress: Adding a thin layer to bring an existing mulch bed back up to depth, not a full new layer
Top-out: The completed stacks and risers, inspected before insulation and drywall, where called separately
Topdressing: A thin layer of compost, soil, or sand spread over turf to smooth, feed, and protect new seed [https://anvilfield.com/field-guides/glossary/topdressing/]
Topping: Cutting stems back to stubs with no regard for laterals, which causes decay and weak watersprout regrowth
Torque-seal: A marking compound striped across a torqued screw and lug to show if it later moved
Torque-to-capacity / Kt: The empirical correlation Qult equals Kt times final installation torque; Kt is the manufacturer's and engineer's factor for the specific shaft and load direction.
Torr / micron: Absolute deep-vacuum units; 1 torr is 1 mm of mercury, 1 micron is one-thousandth of a torr
Torsion spring: Spring on a shaft above the door, wound by drums and cables; stores energy by twisting
Torsion vs extension spring: Torsion winds on a shaft above the door; extension stretches along the side tracks; both store the door's weight as energy
Total air: The full airflow the fan delivers, measured by a pitot traverse in the main and set before branch balancing
Total dynamic head: The vertical lift plus friction loss the pump works against, which sets its real output
Total dynamic head (TDH): The total head a pump must overcome, in feet: the static lift plus the friction head through the force main and fittings at the design flow [https://anvilfield.com/field-guides/glossary/total-dynamic-head-tdh/]
Total energy wheel: A rotating enthalpy wheel that transfers both heat and moisture between the exhaust and the entering outdoor air
Total facility energy: All energy crossing the data center boundary: IT load plus cooling, power losses, lighting, and building systems
Total fixture watts: The sum of the rated wattage of every fixture connected to the transformer
Total float: How long an activity can slip without delaying the project finish
Total float / free float: Slip an activity can take without moving the finish (total) or the next activity (free)
Total flooding: Filling an entire sealed enclosure with agent to a design concentration, rather than aiming at a single object
TPO: Thermoplastic polyolefin, a white, heat-weldable, reflective single-ply membrane at a moderate cost
TPO / PVC: Thermoplastic single-ply membranes whose seams are hot-air welded into one fused material
TR / WR: Tamper-resistant (shuttered, required in dwellings) and weather-resistant (damp and wet locations) [https://anvilfield.com/field-guides/glossary/tr-wr/]
Tracer wire: A continuous conductor laid with plastic pipe so the line can be located later [https://anvilfield.com/field-guides/glossary/tracer-wire/]
Track surfacing: The thin polyurethane or latex surface of binder and rubber granules laid over the base
Track-out: Mud carried onto the public road by tires, controlled by the stabilized construction entrance, and a highly visible violation
Tracker: A single- or dual-axis mount that follows the sun to add production, with a motor, drive, bearings, and a controller that wind-stows in high wind
Trackless tack: An engineered emulsion that breaks to a hard, non-sticky film so traffic and equipment do not pick it up [https://anvilfield.com/field-guides/glossary/trackless-tack/]
Traction vs hydraulic: Traction hangs the car on ropes over a sheave with a counterweight (mid to high-rise); hydraulic uses a pump and a jack to push the car from below (low-rise)
Trade size: The nominal size of conduit or a fitting, called metric designator in the code, not the literal inside diameter [https://anvilfield.com/field-guides/glossary/trade-size/]
Traditional stucco: Portland cement plaster, three coats over lath, about 7/8 in of hard mineral skin
Traffic coating: An elastomeric waterproofing membrane on a concrete deck with an integral aggregate wearing surface for foot or vehicle traffic [https://anvilfield.com/field-guides/glossary/traffic-coating/]
Transceiver / pluggable optic: The module that converts the switch's electrical signal to light and back, in a QSFP-DD or OSFP cage
Transfer air: Air drawn from the conditioned space to make up part of the exhaust
Transfer pump: The pump, usually with a standby, that moves fuel from the bulk tank to the day tank on a level control
Transfer switch (MTS / ATS): A device that moves the load between utility and generator, breaking the utility; manual on a portable set, automatic on a standby set
Transfer time: The interval from loss of normal power to acceptable power at the load; the class sets the limit
Transformer secondary conductor: A conductor on the secondary side of a transformer, unprotected at its supply because the primary device cannot protect it at secondary ampacity; governed by 240.21(C)
Transition zone: The band across the middle of the country where neither cool- nor warm-season grass is fully adapted
Transmittal: The record of what documents were sent, to whom, and when
Transplant shock: Normal first-season stress as a tree runs a full canopy on a cut-back root system; not the same as a dying tree [https://anvilfield.com/field-guides/glossary/transplant-shock/]
Transplanting: Moving an established tree, ball and all, from one location to another, as opposed to planting nursery stock
Transport time: The time for smoke to travel from a sampling hole to the detector, kept under the code maximum, commonly 120 seconds in the Americas
Transverse joint: The connection between duct sections, perpendicular to airflow, such as slip-and-drive or a TDC flange [https://anvilfield.com/field-guides/glossary/transverse-joint/]
Trap: The U-shaped fitting under a fixture that holds a water seal against sewer gas [https://anvilfield.com/field-guides/glossary/trap/]
Trap (water seal): The drain seal that lets water fall by gravity while stopping air from moving through the line
Trap arm: The drain pipe from the trap weir to the vent fitting, limited in length and fall, covered in the DWV and venting guide [https://anvilfield.com/field-guides/glossary/trap-arm/]
Trap primer: A device that adds water to a seldom-used trap to keep its seal from evaporating dry, also called a trap seal primer [https://anvilfield.com/field-guides/glossary/trap-primer/]
Trap seal: The standing column of water held in a trap that blocks sewer gas from the building, measured in inches of depth [https://anvilfield.com/field-guides/glossary/trap-seal/]
Trap seal device: A barrier-type flapper that seals a drain against gas with no water supply, listed to ASSE 1072
Trap seal protection: The code requirement to keep an evaporation-prone trap charged, met by a primer, a barrier device, or a deep-seal arrangement
Trap weir: The top of the trap outlet, the level water rises to before it spills toward the drain; the AAV mounts above it
TRAQ levels: ISA assessment depths: Level 1 limited visual, Level 2 basic 360-degree ground inspection, Level 3 advanced with tools
Travel restraint vs fall arrest: Restraint keeps a worker from reaching the edge so no fall happens; arrest catches a worker after a fall and needs clearance below
Traverse: A grid of velocity readings across a duct, averaged to get true airflow; log-Tchebycheff spacing is the accurate method
Tray fill: The portion of the tray cross-section the cable may occupy, limited by NEC 392.22
Treated-lumber fastener corrosion: The galvanic attack copper-based preservatives drive on regular and electro-galvanized steel, requiring hot-dip galvanized or stainless metal
Tree guard: A cylinder or wrap around a trunk protecting young bark from rabbit and vole girdling and deer rub; removed before it girdles the growing tree
Tree risk assessment: The systematic evaluation of likelihood of failure, likelihood of impacting a target, and consequence, combined into a risk rating
Tree spade: A hydraulic machine whose blades cut and lift a tree and its ball in one cone-shaped piece
Tremie: A smooth steel pipe, commonly 10 to 12 in, used to place concrete from the bottom up under slurry or water without contamination
Trial weld: A daily and per-condition test seam pulled by hand to confirm welder settings before production
Trigger depth: The snow accumulation that starts a plow push, commonly 1 to 2 in, set by the contract
Trim and respond: A reset method that lowers a setpoint at a fixed rate, then raises it in response to requests from zones that cannot keep up
Trip class: Seconds to trip at six times the setting: Class 10, 20, or 30
Trip pressure: Air pressure in the system at the instant the valve unseats, compared against the manufacturer's expected trip point
Triple evacuation: Pulling vacuum, breaking it with dry nitrogen, and repeating three times to dry a wet or contaminated system
Triple-duty valve: A discharge valve combining check, shutoff, and a calibrated balancing function in one body
Triplen: A multiple of the 3rd harmonic; zero-sequence, so it adds in the neutral
Triplen harmonics: Odd multiples of the third harmonic that add on the neutral of a three-phase MWBC [https://anvilfield.com/field-guides/glossary/triplen-harmonics/]
TRIR / DART: OSHA recordable rates per 200,000 hours; TRIR counts all recordables, DART counts cases with days away, restricted duty, or transfer
Trowel: Closes and densifies the set surface; a steel blade pitched steeper each pass
TRT: Thermal response test, an in-situ measurement of formation thermal conductivity for sizing large loop fields
Truck stock / van stock: The parts a service vehicle carries to fix common failures on the first trip
True power factor: Real power over apparent power including harmonics; lower than displacement PF when distortion is present
Truncated dome: A flat-topped raised dome, felt underfoot and by a cane, in a required size and spacing
Trunk caliper: Trunk diameter measured 6 in above grade up to 4 in, or 12 in above grade beyond that, per ANSI Z60.1
TSER: Total Solar Energy Rejected, a single headline figure combining reflected and absorbed-then-reradiated solar energy
TSR: Tensile strength ratio, wet over dry strength; moisture-damage check, often 0.80 minimum
TSR (AASHTO T283): Tensile strength ratio, conditioned over dry strength, the moisture-damage acceptance test
TSS: Total suspended solids, the particulate load in the fluid, trended as a sign of corrosion or biological activity
TTF (time-temperature factor): The Nurse-Saul maturity index, in degree-Celsius-hours
TTR: Transformer turns ratio test, measuring the ratio of primary to secondary turns against the nameplate [https://anvilfield.com/field-guides/glossary/ttr/]
Tuberculation: Rust mounds inside old cast iron that narrow the pipe
Tuckpointing: Strictly, a decorative two-color technique faking fine joints; in common usage, a synonym for repointing
TUE: Total-power Usage Effectiveness, extends the boundary into the IT to capture server fan and supply losses
Tug test: Pulling a sod corner to check whether the roots have anchored into the soil
Turn-of-nut: Pretensioning by a specified nut rotation past snug, verified by match-marks
Turndown: The ratio of maximum to minimum load a valve can control well, wider on pilot-operated valves [https://anvilfield.com/field-guides/glossary/turndown/]
Turnover packet: The proof packet handed to the owner at acceptance of a scope or system, the commissioning record set rolled up with the punch closeout and the signoffs
Turnover rate: The hours to circulate a volume equal to the whole pool through the filter once; set by the health code
Turns ratio: Ratio of primary to secondary winding turns, which sets the voltage ratio
TVOC: Total volatile organic compounds, a single proxy index for a mix of gaseous organics, not a measurement of any one chemical
TWA: Time-weighted average, the noise exposure averaged over an 8-hour shift [https://anvilfield.com/field-guides/glossary/twa/]
TWA / dBA: Time-weighted average noise exposure in A-weighted decibels, the basis for the 85 dBA action level
Two-block: When the hook block runs up into the boom tip, which can part the line and drop the load
Two-factor / MFA: Requiring two of card, PIN, and biometric at a sensitive door
Two-phase cooling: Cooling that removes heat by boiling a dielectric fluid at the heat source and condensing the vapor, carrying heat as latent heat
Two-phase immersion: Immersion where the fluid boils at the chip and condenses on a coil, carrying heat as latent heat of vaporization in a sealed tank
Two-point vs single-point: Two-point hangs the platform on two ropes and two hoists; single-point hangs it on one rope and one hoist
Two-stage: Two PRVs in series that split a large pressure drop for better control and less velocity and noise
Two-stage pump: A vacuum pump with two rotors in series, needed to reach a deep vacuum below 500 microns
Two-stage regulator: First stage drops tank pressure to about 10 psi, second stage to about 11 in w.c.
Two-way cleanout: A fitting allowing a cable to run both toward the building and toward the sewer main
Two-way valve: A throttling coil valve that cuts flow instead of bypassing, what variable flow needs
TXV / EEV: Thermostatic or electronic expansion valve; both hold superheat, so they are charged by subcooling
Type: NFPA 110 class for transfer time, the maximum seconds the load may be without power
Type / Class / Level: NFPA 110 ratings: Type is restore time in seconds, Class is on-site run time in hours, Level is criticality
Type 1 / 2 / 3: SPD classes by install location: line side of the service, load side at panels, and point of use
Type 1 splice: A mechanical splice required to develop at least 125 percent of the bar's specified yield strength, per ACI 318
Type 1 to 4: IEEE PoE classes: af (15.4 W), at (30 W), and bt Type 3 (60 W) and Type 4 (90 W) at the source
Type 2 splice: A splice that meets Type 1 and also develops the bar's specified tensile strength, required in seismic yielding regions
Type 4: Component SPD or assembly built into equipment by the manufacturer, not field-added
Type A / B / C cable: How an array cable is wired internally: straight-through, reversed, or pair-flipped; the cable, not the channel
Type A / B / C tube: Ballast-compatible, ballast-bypass (direct-wire line voltage), and external-LED-driver tube wiring types
Type and Class (hard hat): Z89.1 Type I or II for impact direction, Class G, E, or C for electrical contact
Type B vent: Listed double-wall metal vent for Category I appliances, with a tight clearance to combustibles
Type I hood: A grease hood over cooking appliances, with listed filters, a welded grease duct, clearances, and suppression [https://anvilfield.com/field-guides/glossary/type-i-hood/]
Type I vs Type II hood: Type I handles grease over cooking equipment and is fire-protection equipment under NFPA 96; Type II handles heat and steam only, over dish and oven equipment, with no grease duct
Type II hood: A heat-and-steam hood with no grease, over dishwashers or steam kettles, with no grease duct [https://anvilfield.com/field-guides/glossary/type-ii-hood/]
Type K / L / M: Copper wall thicknesses under ASTM B88, thickest to thinnest, same outside diameter
Type L / K copper: Copper tube wall thicknesses for medical gas, cleaned for oxygen service, commonly to ASTM B819
Type X (fire-rated): A 5/8 in board with a core reinforced to resist fire longer, used in tested fire-rated assemblies; Type C goes further and is not interchangeable
U: Conductance of the assembly in Btu per hour per square foot per degree F, the inverse of R-value
U / RU: Rack unit, 1.75 in (44.45 mm) of vertical mounting height on a 19 in EIA-310 rack
U-factor: The rate of conductive heat transfer through the glazing; film affects it less than it affects SHGC [https://anvilfield.com/field-guides/glossary/u-factor/]
U-factor / R-value: Assembly conductance and its inverse, how the envelope conducts heat
U-factor / SHGC: Heat-loss rate and solar-heat-gain coefficient of the glazing, the two energy numbers that govern selection
U-space / elevation: The U-by-U map of what mounts where in the cabinet, 1U being 1.75 in (44.45 mm) of mounting height
UCS: Unconfined compressive strength, the lab value used to accept a treated layer
UEF: Uniform Energy Factor, the DOE efficiency rating that replaced the older Energy Factor [https://anvilfield.com/field-guides/glossary/uef/]
Ufer: Concrete-encased electrode, 20 ft of 1/2 in rebar or #4 copper in the footing per 250.52(A)(3)
ug/L (ppb): Micrograms per liter, equal to parts per billion, the unit for lead concentration at the tap
UGR: Unified glare rating, lower is less discomfort glare
UL 181: The listing standard for rigid and flexible air ducts and ductboard
UL 181A / 181B: The listings for tapes and closures used on rigid duct (181A) and flexible connectors (181B)
UL 300: The listing standard a kitchen suppression system must meet for modern cooking equipment; pre-UL-300 systems are obsolete
UL 325: The product safety standard for the operator, its entrapment protection, and its usage classes [https://anvilfield.com/field-guides/glossary/ul-325/]
UL 325 entrapment protection: The requirement that a powered door sense an obstruction and reverse, using two independent monitored means
UL 48: The safety standard for electric signs; a listed sign carries markings and installation instructions that are part of the listing
UL 50 / 50E: The standards an enclosure is tested to in order to carry a NEMA type rating
UL 924: The product standard for emergency lighting and exit-sign equipment
UL 9540 / 9540A: The listing for the energy storage system as a product (9540) and the test method for thermal-runaway fire propagation (9540A)
ULSD / B5: Ultra-low-sulfur diesel, often with up to 5 percent biodiesel; both are hygroscopic and shorten storage life
Ultimate load: The overload the system survives without collapse, commonly about twice the rated concentrated load on data sheets; the factor of three is the ICC-ES AC48 safety factor on tested ultimate strength, not an ultimate-to-rated ratio; verify the specified class
Ultrasonic cleaning: Immersion cleaning using cavitation to lift soot and grime from detailed hard goods
Unbilled parts: Parts installed on a job that never reach the customer invoice, a pure margin loss
Unconditional waiver: A lien waiver that takes effect the moment it is signed, whether or not payment is received; do not sign one before funds clear.
Unconfined edge: The free edge of a pass with nothing beside it, which spreads and runs lean under the roller
Underbilled (costs in excess of billings): Work ahead of the billing; your cash funding the job, real profit and cash earned but not yet invoiced
Underbilling: Earned revenue in excess of billings; an asset, since it is work done and not yet billed
Undercut: Excavating soft or unsuitable material and replacing it with compacted structural fill
Underdrain: A perforated pipe in the reservoir that carries off water the soil cannot infiltrate fast enough [https://anvilfield.com/field-guides/glossary/underdrain/]
Underlay / overlay: The physical routed spine-leaf network and the virtual tenant network built on top of it
Underlayment: The secondary water barrier under the shingles, felt or synthetic; it backs up the shingles, it is not the roof [https://anvilfield.com/field-guides/glossary/underlayment/]
Underpinning: Carrying an existing settled foundation down to firm soil on new piers, connected by brackets under the footing, to stop or reverse settlement. [https://anvilfield.com/field-guides/glossary/underpinning/]
Ungrounded conductor / phase / hot: A line conductor, phase colors by convention, not NEC-mandated
Unidirectional / non-unidirectional: Laminar piston flow versus turbulent mixed flow, set by the class
Uniform (distributed) load: Weight spread evenly across the panel, expressed as load per unit area (psf or kPa) [https://anvilfield.com/field-guides/glossary/uniform-distributed-load/]
Uniformity ratio: Evenness of the light across the grid, as max-to-min or average-to-min
Unit cooler / evaporator TD: The unit cooler is the in-box finned evaporator with fans; TD is the temperature difference between the coil's refrigerant saturation and the entering air, which sets capacity and humidity
Unit cost: The cost to install one unit of an item, labor and material together
Unit equipment: Self-contained emergency light with its own battery, charger, and transfer (the bug eye)
Unit heater: A self-contained heater and fan in one hung cabinet that blows warm air directly into the space, with no ductwork
Unit price vs lump sum: Unit price pays measured quantities at set rates; lump sum is one price for the whole scope
Universal precautions: Treating all human blood and certain body fluids as if known to be infectious for bloodborne pathogens, the principle under OSHA 1910.1030
Universal waste: EPA category (40 CFR 273) for simplified handling of spent mercury lamps and similar wastes
Unvented conditioned attic: An attic foamed at the roofline and brought inside the building envelope, with no ventilation
Upblast fan: A roof exhaust fan that discharges vertically up and away from the roof, used for dirty or greasy air [https://anvilfield.com/field-guides/glossary/upblast-fan/]
Upfeed: Distribution that pushes water up from the bottom on street or pump pressure
Uplift zone: The field, perimeter, or corner band under ASCE 7; the corner sees the highest suction
UPS: Uninterruptible power supply, which conditions power and carries the load through a source disturbance from stored energy [https://anvilfield.com/field-guides/glossary/ups/]
UPS bypass: The mode that routes load around the UPS inverter; the EPO must stop the UPS from feeding the room, not just shift it to bypass
Uptime Tier: The Uptime Institute rating of facility redundancy, Tier I through Tier IV
Usable / inside area: Inside width times depth of the tray, with depth capped at 6 in for the NEC multiconductor fill rules
Usable capacity: Installed capacity minus the redundancy reserve and the continuous-load derate [https://anvilfield.com/field-guides/glossary/usable-capacity/]
Usable storage: The fraction of tank volume delivered before the outlet sags, commonly 70 to 80 percent
Usage class I to IV: I residential, II commercial or general access, III industrial or limited, IV restricted or guarded high-security
USC FCCCHR: The USC Foundation for Cross-Connection Control and Hydraulic Research, source of the common field test procedure
USDOT number: The FMCSA identifier for a motor carrier, kept current with the biennial MCS-150 update
Use case: The specific operational decision the twin is built to support
Use zone / fall zone: The surfaced, obstacle-free area around equipment where a falling child lands; 6 ft minimum, larger for swings and slides
UST: Underground storage tank, a tank with 10 percent or more of its volume buried, governed by EPA 40 CFR 280
Utilization: Used capacity as a share of usable capacity, after the continuous derate and the redundancy reserve [https://anvilfield.com/field-guides/glossary/utilization/]
Utilization / billable hours: The share of a technician's paid time that lands on a customer invoice
UTS: Universal total station, a robotic instrument giving millimeter-class machine position
V: Stored water volume in gallons, the usable cold volume the tank delivers
V<sub>awg</sub>: Volume allowance for that wire size from Table 314.16(B)
V<sub>box</sub>: Box volume from 314.16(A) or the volume marked on the box
V<sub>device</sub>: Allowance for the largest conductor connected to the device, counted twice per device
Va / air voids: Air left in the compacted mix as a percent of volume, designed to 4 percent
VA / kVA: Volt-amperes, the apparent power that sizes conductors and gear; kVA is thousands of VA
Vacuum breaker: Backflow protection built into a potable supply-fed primer that stops drain-side water being siphoned back into the potable system [https://anvilfield.com/field-guides/glossary/vacuum-breaker/]
Vacuum test: A negative-pressure test, the code option for plastic DWV instead of a positive air test
Vacuum vs SF6 breaker: Vacuum interrupts the arc in a sealed vacuum bottle; SF6 interrupts in pressurized sulfur hexafluoride gas
Value = function / cost: The core relationship: value rises when function is held and cost falls, or when function is added for the same cost
Value engineering: A structured method to improve a project's value by analyzing required functions and delivering them at lower life-cycle cost without losing performance [https://anvilfield.com/field-guides/glossary/value-engineering/]
Valve authority: Ratio of the valve's pressure drop to the controlled branch drop; aim high, commonly 0.3 to 0.5 or better [https://anvilfield.com/field-guides/glossary/valve-authority/]
Valve protection cap: The threaded cover that protects the cylinder valve from a knock when no regulator is attached
Van-accessible space: The wider accessible variant: 11 ft plus a 5 ft aisle, or 8 ft plus an 8 ft aisle, with 98 in clearance [https://anvilfield.com/field-guides/glossary/van-accessible-space/]
Vanity metric: A number that looks impressive but drives no decision, such as revenue without margin
Vapor barrier: A retarder on the warm, pool side of walls, roof, and floor that stops moist air from condensing inside the assembly [https://anvilfield.com/field-guides/glossary/vapor-barrier/]
Vapor barrier / vapor retarder: The continuous skin that stops humid air from reaching the cold pipe; sealed at every joint
Vapor barrier vs vapor retarder: Barrier is 0.1 perms or less; retarder is 0.1 to 1.0 perms and only slows vapor
Vapor intrusion: Migration of VOC vapors from contaminated soil or groundwater up into a building through the soil-gas pathway
Vapor pressure: The push that moves water vapor from wet materials toward drier air; drying follows the gradient [https://anvilfield.com/field-guides/glossary/vapor-pressure/]
Vapor retarder: A layer that slows water vapor diffusion through the assembly, rated by perm; a vapor barrier is the lowest-perm version, Class I at 0.1 perm or less [https://anvilfield.com/field-guides/glossary/vapor-retarder/]
Vapor vent: Independent vent carrying flammable vapor from the separator to outside air, separate from sanitary venting
Vapor-compression cycle: The four-part loop, compressor, condenser, metering device, evaporator, that moves heat using a refrigerant that changes state
Vaporization: Liquid propane boiling to vapor in the tank, which slows in cold and under high load
Variable primary flow (VPF): One variable-speed pump set through the chillers and coils, with a minimum-flow bypass protecting the evaporator
Variable retainage / step-down: A contract term that reduces the retainage rate, or caps it, at a milestone such as 50 percent complete; some states require it.
Variable torque vs constant torque: Load type that sets drive duty: pumps and fans (normal duty) vs full torque at low speed (heavy duty)
Variable-pitch sheave: An adjustable sheave whose movable flange changes pitch diameter to trim fan speed
Variegated: The mottled, marbled, uneven color an acid stain produces, where the slab and the reaction drive the look
VAV box: Variable air volume terminal unit; a controlled damper, flow sensor, and optional reheat that conditions one zone [https://anvilfield.com/field-guides/glossary/vav-box/]
Vbz / Voz / Vot: Breathing-zone, zone, and system outdoor airflow in the 62.1 rate procedure
VCSEL: Vertical-cavity surface-emitting laser, the low-cost 850 nm source for multimode SR optics
VCT: Vinyl composition tile, a budget hard tile that needs wax and ongoing maintenance
Vd / percent drop: Volts lost in the conductor, and that loss as a percentage of source voltage
VECP: Value engineering change proposal, a contractor-initiated proposal on public or federal work where accepted savings are shared with the owner
Vector group: The phase relationship between primary and secondary, shown as a clock position such as Dyn11
Vegetation-free zone: A gravel or paver border at the perimeter and around penetrations for wind scour resistance, access, and fire breaks [https://anvilfield.com/field-guides/glossary/vegetation-free-zone/]
Vegetative / green / living roof: A planted assembly built over a watertight roof membrane for stormwater, cooling, amenity, and membrane protection [https://anvilfield.com/field-guides/glossary/vegetative-green-living-roof/]
Vehicle restraint: A device that locks a trailer to the dock by its rear impact guard or wheel to stop creep and early departure
Vehicular vs pedestrian system: Vehicular systems are built thicker with more aggregate for tires; pedestrian systems are lighter for foot traffic
Velocity: Speed of the air stream, at the nozzle and, more importantly, at the floor, in ft/min or m/s
Velocity pressure: The pressure from air motion that a pitot tube reads and converts to velocity, distinct from static pressure
Velocity pressure (VP): The pressure from air motion the inlet sensor reads, converted to CFM through the K-factor
Vented / unvented: Whether combustion products go outside through a flue or into the space, which sets the ventilation requirement
Ventilation interlock: The link that runs or boosts the exhaust on a hydrogen detection signal
Ventricular fibrillation (VF): A disorganized heart rhythm that pumps no blood; the shockable rhythm an AED is built to correct
Verification: Confirming an alarm is real, by call or video, before police respond; a verified alarm gets priority, an unverified one may get none
Verified alarm: An alert a human or AI service has confirmed as a real event before it triggers a response
Verifier (ASSE 6030): The independent third party who tests and certifies the finished system, separate from the installer
Version / revision: A numbered, dated issue of a document; the current revision supersedes the prior one
Vertical manager: A full-height cable channel on the side or rear of a rack that carries cable up and down
Very-early warning: Detection at the incipient, off-gassing stage before visible smoke, the class of detection a data center buys
VFA: Voids filled with asphalt, the share of VMA filled by effective binder; banded by traffic
VFD: Variable-frequency drive on the pump, letting the CDU modulate flow to hold its control target and ramp on a pump loss [https://anvilfield.com/field-guides/glossary/vfd/]
VFD / ASD / VSD / inverter: Names for the same device that varies motor speed by varying output frequency and voltage
VFD / variable-speed: A variable frequency drive that throttles pump speed to hold a discharge pressure setpoint across changing demand
VFL: Visual fault locator, a red laser pen that confirms continuity and which physical fiber position lights up
VGB Act: The Virginia Graeme Baker Pool and Spa Safety Act, the federal anti-entrapment law requiring compliant covers and secondary protection
VGB anti-entrapment drains: Main drains built to the Virginia Graeme Baker Act: compliant covers to ANSI/ASME A112.19.8, dual drains spaced so one body cannot block both, and an SVRS or other secondary system where required.
Vibration analysis / FFT: Reading mechanical vibration; the fast Fourier transform breaks it into a frequency spectrum that names the fault
Vibration isolator: A spring or neoprene mount under the pump that keeps its vibration out of the structure
Vibratory truss screed: A vibrating blade or truss run form to form that strikes off and consolidates
Video surveillance / CCTV: Cameras, a recorder or VMS, storage, and the network that carries the video; designed to capture a scene at a chosen detail level
Visual line of sight (VLOS): The Part 107 rule that the pilot or a visual observer must keep eyes on the aircraft throughout the flight, absent a waiver.
VLF: Very-low-frequency AC withstand testing, around 0.1 Hz, the modern field acceptance test for shielded MV cable
VLF / partial discharge testing: VLF applies a 0.1 Hz AC withstand voltage; PD testing finds and locates local insulation defects; tan delta reads overall condition
VLT: Visible Light Transmittance, the percent of visible light the filmed glass passes; high is clear, low is dark
VM: Vertical multiplier, for the height of the hands at the start of the lift
VMA: Viscosity-modifying admixture, which thickens the paste to hold the aggregate in suspension [https://anvilfield.com/field-guides/glossary/vma/]
VMS: Video management system, the platform that records, stores, and serves CCTV
Voc: Module open-circuit voltage from the nameplate, measured at the 25 degree C rating temperature
Voc / Voc(cold): Open-circuit module voltage, and that voltage corrected up for the coldest expected temperature
VOCs / TVOC: Volatile organic compounds that off-gas from materials; TVOC is their lumped screening sum, not a single compound
Voice evacuation: A spoken emergency instruction to evacuate or shelter, delivered by the fire alarm or emergency communication system
Void content: The percent of the volume that is connected air space, commonly about 15 to 25 percent, that carries the water
Void content / void ratio: The share of a material or stone layer that is open space; the storage capacity of the reservoir
Voltage class (gloves): Rubber insulating glove rating, class 00 to 4, by maximum use voltage, for shock not arc
Voltage drop: Volts lost in the cable over distance under load, which dims fixtures at the far end of a run
Voltage match: Incoming set and bus equal in magnitude before close, so no reactive surge on tie
Voltage to ground: The voltage between a conductor and ground, the value that selects the depth row, not phase-to-phase voltage
Volume allowance: The cubic inches Table 314.16(B) assigns to each conductor size for the count
VoP: Velocity of propagation, the pulse speed in the cable that converts time to distance
VPF: Variable primary flow, one variable-speed pump set serving both the chillers and the coils
VPR: Voltage protection rating, the let-through voltage during a standard surge; lower clamps tighter [https://anvilfield.com/field-guides/glossary/vpr/]
VRAM / longitudinal joint sealant: A void-reducing membrane placed hot under the joint before paving; it migrates up into the seam to fill voids and cut permeability [https://anvilfield.com/field-guides/glossary/vram-longitudinal-joint-sealant/]
VRF: Variable refrigerant flow, advanced split DX with one outdoor unit feeding many indoor units, often with heat recovery
VRF / VRV: Variable refrigerant flow / variable refrigerant volume, the same modulating multi-split technology under different trademarks [https://anvilfield.com/field-guides/glossary/vrf-vrv/]
VRLA: Valve-regulated lead-acid, the sealed lead-acid battery; fails by dry-out and impedance rise
VRLA / VLA: Valve-regulated (sealed) lead-acid and vented (flooded) lead-acid, the two lead-acid families with different maintenance and rooms [https://anvilfield.com/field-guides/glossary/vrla-vla/]
w: Uniform pressure: total weight W divided by the footprint area A it bears on
W / V / G / ST: Soil and waste, vent, gas, and storm drain; W also shown as SAN or SS
w, h: Unit weight of the concrete in pcf and the full height of fresh concrete in the form in ft, which set the full-liquid-head cap
W-class: ASHRAE TC 9.9 facility water supply temperature class, W17 through W+, the number being the max supply temperature in degrees Celsius [https://anvilfield.com/field-guides/glossary/w-class/]
w/c (or w/cm): Mass of free water divided by mass of cementitious material; w/cm when supplementary cementitious materials are included
w/c (w/cm): Mass of water divided by mass of cementitious material; the master variable for strength and permeability
W/D or A/P ratio: Section factor, weight or area over heated perimeter, that drives the thickness; heavier members need less
W/ft: Watts per foot, the cable's heat output, matched to the pipe's heat loss
w_c: Weight correction factor for three conductors in the conduit, often around 1.4 when they ride cradled in the bottom, and closer to 1.2 for a true triangular (trefoil) arrangement
WAGD: Waste anesthetic gas disposal, the system that scavenges exhaled anesthetic so it does not pool in the room
Wage determination (WD): The official schedule of classifications and their base and fringe rates for a locality and construction type
Waiver of subrogation: Giving up your carrier's right to recover from a third party it would otherwise pursue
Walk-in: An insulated box, cooler or freezer, built from foamed panels with a sealed door and vapor barrier, cooled by a unit cooler fed from a remote condensing unit
Walking body voltage: Peak voltage a person builds walking the floor in their footwear; commonly held under 100 V peak per STM97.2
Walkway pad: A sacrificial wear surface adhered or welded to the membrane to protect it from foot traffic and tools
Wall saw / track saw: Track-mounted diamond blade for vertical and precise deep cuts
Wall sleeve: The permanent steel box in the wall, standard 42 by 16 inches, that the chassis slides into
Wall tie: The corrosion-resistant anchor that ties a veneer back to its structural backup
Wall tie / free-standing height: The engineered anchor tying the mast to the building, and the height the mast can stand before it needs the first tie
Warm wall line: The inside face of the exterior wall, the line the eave ice barrier must extend past
Warm-season grass: Turf adapted to southern climates that grows best at 80 to 95 degrees F and goes dormant after frost [https://anvilfield.com/field-guides/glossary/warm-season-grass/]
Warning line / designated area: A warning-line-bounded zone on a low-slope roof where infrequent, temporary work is allowed away from the edge without conventional protection
Warping: Often used the same as curling; some references reserve it for the moisture-gradient edge lift
Warranty claim: A request to the manufacturer to cover a part that failed under its warranty term [https://anvilfield.com/field-guides/glossary/warranty-claim/]
Warranty reserve: Money set aside against the warranty cost a job is expected to generate later, so the cost is matched to the job instead of surprising a future month. Also called a warranty accrual. Treatment is the CPA's.
Warranty rider: A written manufacturer approval keeping the watertight warranty in force with the array installed
Wash-water containment / reclaim: Capturing the runoff with drain covers, berms, and a vacuum, then reusing or disposing of it legally
Washboarding: Regular corrugations from traffic on a dry, loose, poorly bound surface; also called corrugation
Washout: The contained area for cleanout slurry and waste prime, kept out of storm drains and off-site soil
Washout test: Washing a fresh sample to recover and weigh the fibers, confirming the dose in the load
Waste factor: The percentage added to the measured material to cover cuts, offcuts, and damage [https://anvilfield.com/field-guides/glossary/waste-factor/]
Waste fitting: The cast hub built into a water closet carrier that the bowl discharges into and that connects to the branch or stack
Waste heat recovery: Capturing the heat a data center would reject and putting it to use instead of dumping it
Water balance / LSI: The Langelier Saturation Index from pH, temperature, alkalinity, calcium, CYA, and TDS; near 0 is balanced, high scales, low corrodes
Water bond: A conductive surface in contact with the water, commonly at least 9 sq in, tied into the grid
Water budget / seasonal adjust: A percentage that scales every zone's run time up or down by season; also a utility's annual gallon allocation for a site
Water closet: The plumbing trade name for a toilet, flushed by a gravity tank, a pressure-assist tank, or a flushometer
Water closet carrier: A floor-mounted carrier with the toilet's waste fitting built into the frame, the most common carrier on the job
Water delivery time: Time for water to reach the inspector's test connection, measured from when that connection is fully opened; commonly held to 60 seconds on qualifying systems
Water hammer: The hydraulic shock from filling a system too fast, which can split a fitting or mainline at spring startup [https://anvilfield.com/field-guides/glossary/water-hammer/]
Water hammer arrestor: A sealed device with a permanent air or gas charge that absorbs the surge, listed to ASSE 1010 / PDI WH-201
Water mist: A system of very fine water droplets that cool and locally smother with far less water than a sprinkler, governed by NFPA 750
Water mitigation: Emergency work of stopping the source, extracting, and drying to limit the loss before repairs
Water test / hose test: Reproducing a leak with controlled water, worked in small zones from low to high
Water to cement ratio (w/c): Mass of water over mass of cementitious material; low w/c mixes bleed less and crack plastically more easily [https://anvilfield.com/field-guides/glossary/water-to-cement-ratio-w-c/]
Water vs wastewater treatment: Drinking-water treatment makes raw water safe to consume; wastewater treatment cleans used water before discharge to the environment
Water well: A cased hole drilled to an aquifer, with a pump that lifts groundwater to the building
Water-based stain (non-reactive): Pigment in water or solvent that lodges in the pores for a wider, more uniform color, with no chemical reaction
Water-cement ratio (w/c): The mass of water to cement; lower means higher strength and lower permeability
Water-cement ratio (w/c, w/cm): Weight of water to cementitious material, tight in pervious at roughly 0.27 to 0.34 per the mix design
Water-powered backup: A backup that uses municipal water pressure through a venturi to pump the sump, no battery needed
Water-resistive barrier (WRB) / drainage plane: The lapped layer behind the siding, house wrap or felt, that drains water that gets past the cladding down and out
Waterfront permit: The federal, state, and local authorizations required to build in the water, including Army Corps and submerged-land approvals
Waterline tile / coping: The tile band set at the water level on the bond beam, and the coping cap on the pool edge that sheds water away and transitions to the deck across an expansion joint.
Waterlogged: A failed expansion tank whose bladder has ruptured, so water has filled the air side and there is no cushion left
Waterproofing: A treatment that resists water under hydrostatic pressure, typically a membrane
Waterproofing / wall protection: The moisture barrier, air gap, drainage plane, and root barrier that keep constant water and roots off the building structure
Waterproofing membrane / flood test: An ANSI A118.10 bonded sheet or liquid layer under tile in wet areas, proved by holding about 2 in of water in the pan for 24 hours before tiling.
WaterSense: The EPA efficiency label for irrigation controllers verified to save water, and the gate for most utility rebates [https://anvilfield.com/field-guides/glossary/watersense/]
Waterside economizer: An economizer that makes cold water with the cooling tower and a plate-and-frame heat exchanger, chiller off
Waterside economizer / free cooling: Making chilled water with the cooling tower alone, chiller off or unloaded, when the wet-bulb is low enough
Waterstop: A continuous barrier cast into or applied across a concrete joint to block water [https://anvilfield.com/field-guides/glossary/waterstop/]
Watertight / hosedown: The Type 4 duty: keeps out splashing and hose-directed water, and is dust-tight
Watt density: Electric snow-melt load in watts per square foot, set by cable spacing and climate
Watts: Power a string or display draws; sum the watts on a run or circuit to find the load
Wave equation: A model of the hammer, pile, and soil that relates blow count and stress to capacity, run in GRLWEAP
Waviness index: ASTM E1486 measure of mid-wavelength deviation, 2 to 10 ft, that affects rolling ride and FF does not sense
Wax ring: The seal between a toilet outlet and the closet flange; a failure leaks gas and water at the base
Wax ring / gasket: The seal between the toilet bowl horn and the closet flange, compressed when the bowl is set and bolted down
WBGT: Wet bulb globe temperature, which adds sun, wind, and radiant heat, the measure NIOSH and ACGIH use for occupational heat
WBS: Work breakdown structure: the job split into the activities you schedule, broken by area and operation
WCR: Withstand and closing rating, the short-circuit current the switch can survive and close into, per UL 1008
WDM: Wavelength-division multiplexing, carrying several signals on one fiber by using different colors of light
Weaning: Stretching the watering interval and widening the wetted zone over time so the tree learns to find water on its own
Wearing course: The surface gravel a road's tires ride on, dense-graded with clay binder
WEEB: Washer for electrical equipment bonding; teeth bite the frame coating to bond the array
Weekly work plan / commitment: The week's set of reliable promises, made only to work whose constraints are cleared
Weep / drained glazing pocket: Sill openings that drain water out of the glazing pocket so the IGU edge does not sit in standing water
Weep channel: A condensation gutter in the skylight frame that drains collected moisture to weep holes outside
Weep hole: The opening at the flashing line that drains the collected water back out [https://anvilfield.com/field-guides/glossary/weep-hole/]
Weep holes: Openings at liner level in a clamping drain that let water in the mortar bed drain out [https://anvilfield.com/field-guides/glossary/weep-holes/]
Weep screed: The metal base termination that drains water out and holds the cladding off the ground
Weir: The downstream lip of the trap where water spills over toward the drain [https://anvilfield.com/field-guides/glossary/weir/]
Well disinfection: Shock chlorination of the well and plumbing after drilling or repair, followed by a confirming retest
Well screen: The slotted intake in the aquifer that admits water and holds back sand, sized by slot to the formation or gravel pack
Wellpoint: A small-diameter, shallow well on a common header and vacuum pump, used in groups to draw down sand
Wenner method: The four-pin soil resistivity test, where the reading reflects soil to about the pin spacing
Western red cedar / grade: The standard cedar species; CSSB grades it No. 1 (Blue Label, clear heartwood, edge-grain), No. 2, and No. 3
Wet / damp / dry location: NEC location categories that decide the method and the conductor
Wet bulb: Temperature that reflects air moisture, used to read the split against humidity
Wet bulb / dry bulb: Air temperatures with and without evaporative cooling; together they give humidity and the load input for a superheat chart
Wet chemical: The potassium-based liquid agent that saponifies and cools a grease fire; the system type UL 300 requires for cooking hazards
Wet cleaning: Removing bonded residue with a chemistry matched to the residue and surface, after dry cleaning
Wet location: Underground, outdoor, or fillable raceway; requires a W-rated insulation
Wet mils: Thickness of a liquid membrane while wet, in thousandths of an inch, set by the maker
Wet pipe: A sprinkler system charged with water at the heads, ready to flow on a fused head; the code baseline, avoided over live racks
Wet pipe system: Pipe kept full of water; the head opens and water flows immediately; the default for heated space
Wet screed: Striking off to wet reference pads or form edges by eye; cheap and least accurate
Wet smoke: Smeary, sticky residue from a slow, low-heat fire in plastics and synthetics, the hardest to clean
Wet soot: Greasy, sticky residue from a slow, smoldering fire; wet-cleaned with a degreaser and mechanical action
Wet stacking: Unburned fuel and soot building up in a diesel run too lightly to reach full combustion temperature [https://anvilfield.com/field-guides/glossary/wet-stacking/]
Wet tap: Tapping a main under pressure with a sleeve, valve, and tapping machine, cutting and retaining a coupon without taking the main out of service
Wet vent: A drain pipe, oversized so it never runs full, that also serves as the vent for downstream fixtures, common on bathroom groups [https://anvilfield.com/field-guides/glossary/wet-vent/]
Wet vs dry glazing: Sealing the glass with tape or sealant against the frame, versus holding it with compression gaskets
Wet well: The tank that collects the incoming wastewater between pump cycles; its working volume is the storage between the pump-on and pump-off levels
Wet-bulb: The lowest temperature evaporation can reach, the floor the tower works against and the driver of free-cooling hours [https://anvilfield.com/field-guides/glossary/wet-bulb/]
Wet-bulb depression: The gap between dry-bulb and wet-bulb; the cooling potential available to an evaporative system
Wet-bulb temperature: The temperature air reaches when saturated by evaporation; the floor an evaporative cooler approaches but never beats [https://anvilfield.com/field-guides/glossary/wet-bulb-temperature/]
Wet-film / dry-film mils: Wet film is thickness as applied; dry film is what remains after cure, the number the spec is written to
Wet-mix / dry-mix: Water batched before the hose (wet) versus water added at the nozzle by the nozzleman (dry)
Wet-rotor circulator: An inline circulator whose motor rotor spins in the pumped water, cooling and lubricating the bearings with no mechanical seal to leak
WFT: Wet film thickness in mils, the coating depth right after application, before it cures
WFT / DFT: Wet film thickness, the gauge reading right after application, and dry film thickness, the cured depth the warranty is written to
While-in-use cover: A weatherproof receptacle cover, the bubble cover, that stays weatherproof with a cord plugged in
Whip: The flexible conduit branch drop from the panel to a receptacle at the rack
White space: The conditioned data hall where the IT racks and servers sit
White space / gray space: The conditioned data hall for IT gear, and the support area for the mechanical and electrical plant
Whitetopping: A concrete overlay placed over existing asphalt, forming a composite pavement
Widowmaker: A dead, broken, or hung-up limb overhead that can drop when the tree is worked
Win rate / hit rate: Jobs won divided by jobs bid; also expressed as a bid-to-win ratio like 4-to-1
Wind bracing / flange brace: Rod or cable X-bracing that resists lateral load in braced bays, and the short angle that holds a frame flange from buckling
Wind clip: A metal clip at the tile nose or side that resists uplift, standard in coastal and high-wind work
Wind load: The force and overturning moment the wind puts on the sign's exposed area, the load that controls structural design
Wind rider: An add-on extending coverage to wind damage up to a stated speed, such as 55, 72, or 110 mph
Wind uplift: The lifting force wind exerts on the array and roof, worst at corners and perimeter, set by ASCE 7 [https://anvilfield.com/field-guides/glossary/wind-uplift/]
Wind uplift / lateral load: The upward pull and sideways push wind delivers; uplift lifts the structure, lateral load racks it
Window film: A thin polyester layer applied to existing glass to add solar control, safety, security, privacy, or graffiti resistance
Windrow: The continuous line of snow a plow casts to the side as it pushes
Windshield time: The non-billable hours a technician spends driving between jobs
Winter heating penalty: The small rise in heating energy from a reflective roof turning away weak winter sun
Winterizing: Shutting off, draining, and blowing out the water lines and protecting the trap so they do not freeze and split in a cold climate
WIP: Work in progress: tracks percent complete against percent billed on multi-period jobs
WIP (work-in-progress) schedule: A report of all open contracts showing contract value, costs, completion, earned revenue, and billings
WIP schedule: Work-in-progress report comparing cost incurred and percent complete to billings, job by job, to show over/underbilling and fade
Wire mesh / basket tray: Welded mesh tray, light and field-formed, the standard for LV, data, and fiber
Wire saw: Diamond-beaded wire for thick, massive, or odd-shaped cuts a blade cannot reach
Wireway: A covered metal or nonmetallic trough used as a raceway for many conductors, NEC Article 376 or 378
Within sight (in sight from): Visible and not more than 50 ft from the equipment, per the NEC definition; confirm against the adopted edition
Withstand rating: Fault current the bus and structure can take, with short-time gear rated to hold it for an interval such as 30 cycles
Witness / signoff: The independent person who attests a test happened as recorded, and the signature that closes an item; the inspect, witness, and accept chain
Witness mark: A brittle paint stripe across a torqued fastener and its body that shows it was torqued and cracks if it later moves
Witness point: An inspection the witnessing party is notified of and may attend; work may proceed if they do not, after notice [https://anvilfield.com/field-guides/glossary/witness-point/]
WLL (working load limit): The maximum load a sling or fitting is rated to carry, marked by the manufacturer, with the design factor already included
WMA: Warm mix asphalt, the same mix produced and placed roughly 30 to 100°F cooler than hot mix [https://anvilfield.com/field-guides/glossary/wma/]
WMA / warm mix asphalt: Asphalt produced at a lower temperature using an additive or foaming process
WOG / CWP: Water-oil-gas or cold working pressure, the maximum non-shock pressure at ambient temperature
Wood shake vs wood shingle: A shake is split, so it is thick, rough, and irregular; a shingle is sawn on both faces, so it is thinner, smooth, and uniform
Wood-burning vs gas: Open wood fire with sparks and smoke, versus a controllable gas burner over rated media
Work in progress (WIP): Cost put into a job that is not billed yet; underbilling ties up your cash inside the job
Work letter: The lease exhibit that defines who builds and pays for what, the base-building scope, and the allowance terms
Work order (job ticket / service order): The single record of one job from the call to final payment
Worker tag (RFID / UWB): The transponder a worker carries so a machine's antenna can detect them. RFID covers a broader range; ultra-wideband resolves position to the centimeter for tighter, tunable zones.
Workforce development: Defining roles, training and certifying people, building hiring pipelines, transferring knowledge, and retaining the team
Working capital: Current assets minus current liabilities, the short-term cash strength a reviewer and a surety read most closely [https://anvilfield.com/field-guides/glossary/working-capital/]
Working crack: A crack that opens and closes more than about 1/8 in with temperature, needing a flexible seal
Working distance: The distance from arc source to the worker's face and chest the incident energy is reported at; typically 18 to 36 in by gear type
Working envelope: The range of reach, height, and angle the machine is rated to operate within
Working space: The clear depth, width, and height the code reserves in front of gear worked on energized, for access and escape
Working time / flow life: The window after mixing to place and roll the material, often about 15 to 20 minutes at 70 degrees F
Working vs non-working crack: A crack that opens and closes with temperature versus one that barely moves; sets seal vs fill
Workmanship warranty: Your promise that the install was done correctly. Covers your labor and your details, commonly for about a year, but your contract controls the scope and the term. [https://anvilfield.com/field-guides/glossary/workmanship-warranty/]
Workweek: A fixed, recurring seven-day period the employer sets, the basis for the FLSA 40-hour overtime threshold
World Athletics certification: Class 1 or Class 2 testing and measurement that qualifies a track for sanctioned competition
Woven vs nonwoven: Woven is high strength and low flow for separation and reinforcement; nonwoven is high flow for filtration and drainage.
WPS: Welding procedure specification, the recipe bounding process, filler, preheat, interpass, and parameters
WPS / PQR: Welding procedure specification and the procedure qualification record that backs it, per ASME Section IX [https://anvilfield.com/field-guides/glossary/wps-pqr/]
WQv: Water quality volume, the runoff the basin is sized to capture and treat, set by the local manual and permit [https://anvilfield.com/field-guides/glossary/wqv/]
WRB / drainage plane: The water-resistive barrier and the gap behind the cladding that drains water down and out
WSFU: Water supply fixture unit, a dimensionless load value for a fixture, folding flow, duration, and frequency of use
WSP: Working steam pressure, the separate lower rating for saturated steam
WUCOLS: Water Use Classification of Landscape Species, the UC reference rating plant water use from very low to high by region
WUE: Water usage effectiveness, water used per unit of IT energy, in liters per kilowatt-hour; lower is better [https://anvilfield.com/field-guides/glossary/wue/]
WUE / PUE: Water usage effectiveness and power usage effectiveness; the water-versus-energy scorecard for data-center cooling
Wye (star, Y): A connection with a common neutral point; line-to-line voltage is 1.732 times line-to-neutral, line current equals phase current
Wythe: One unit thickness of a masonry wall
X-factor: ASHRAE's relative hardware failure rate indexed to a 20 C inlet baseline of 1.0
X/R ratio: System reactance over resistance, which sets how high the asymmetrical first-cycle peak runs
Xeriscape: Low-water landscaping that fits plants, soil, and irrigation to a dry climate; coined by Denver Water in 1981 from xeros, dry
XHEZ: UL category code for through-penetration firestop systems in the directory
XHHW / XHHW-2: Cross-linked polyethylene, high heat, wet rated; XHHW-2 is 90C wet and dry
Yield: The gpm the well sustains over time, the ceiling on pump sizing [https://anvilfield.com/field-guides/glossary/yield/]
Yield / spread rate: Tons placed per area, in lb per square yard, compared to a target near 110 lb per square yard per inch of thickness
Yoke / strap: The mounting frame of a device, the reason a receptacle or switch counts as two
Zero-pressure accumulation: Zone logic that backs product up without the cases pressing on each other, so a sorter or scanner can meter them
Zero-sequence sensing: A single window CT around all conductors that reads the net imbalance directly
Zeroscape: Gravel and rock with few or no plants; the bare, hot look xeriscape is mistaken for, not the same thing
Zinc whisker: A conductive zinc crystal grown from electroplated zinc by internal stress, which breaks loose and shorts electronics
Zinc-rich primer: A primer loaded with metallic zinc that protects the steel galvanically even at a scratch or holiday
Zombie server: A powered-on machine doing no useful work that holds power, cooling, space, and ports for nothing
Zone: An area conditioned and controlled on its own, with its own thermostat and damper [https://anvilfield.com/field-guides/glossary/zone/]
Zone control panel: The board that reads thermostat calls, drives the dampers, and stages the equipment
Zone damper: A motorized blade in the duct that opens and closes to direct air to a zone
Zone flow demand: The sum of every emitter's GPH on the zone, converted to GPM, that the supply must deliver
Zone of protection: The volume under the chord of the rolling sphere where the structure is shielded by the terminals
Zoning: Dividing the system so a page or message reaches one area without sounding everywhere, and so priority can be enforced
ZSI: Zone-selective interlocking; breakers signal each other so the upstream device trips fast only for a fault in its own zone [https://anvilfield.com/field-guides/glossary/zsi/]
α: Coefficient of thermal expansion for the material, from the manufacturer
ΔL: Change in pipe length, the movement you have to absorb
ΔT: Temperature rise, the setpoint minus the cold inlet, in degrees F, taken on the coldest-month inlet
εr: Relative dielectric of the concrete, roughly 6 to 8 dry, higher when wet; sets the pulse velocity
η (eta): Thermal efficiency factor by process: SAW near 1.0, SMAW/GMAW/FCAW near 0.8, GTAW near 0.6
ρ (rho): Soil resistivity in ohm-meters, or ohm-centimeters in older tables
#15 / #30 felt: Asphalt-saturated felt by an old weight-per-square convention, #30 being the heavier, tougher roll
$/MW / $/kW: Cost per megawatt or kilowatt of IT capacity, the common way data center capital cost is benchmarked
% Gmm: In-place density as a percentage of Gmm; 100 percent minus % Gmm is roughly the air-void content
% Gmm / air voids: In-place density as a percentage of the theoretical maximum specific gravity; the remainder is roughly the air-void content [https://anvilfield.com/field-guides/glossary/gmm-air-voids/]
%Z: Transformer percent impedance from the nameplate, the percent of rated voltage that drives full-load current into a shorted secondary [https://anvilfield.com/field-guides/glossary/z/]
%Z (percent impedance): Winding impedance as a percent of rated values; sets the downstream available fault current
&alpha;: Fiber attenuation in dB per km, higher at shorter wavelengths, from the fiber data sheet
&rho; (rho): Soil resistivity, in ohm-meters or ohm-centimeters
-850 mV criterion / reference electrode: A polarized potential of -850 mV or more negative versus a copper/copper-sulfate electrode, the standard proof of protection in soil
0-10V: Analog dimming over a low-voltage control pair, 10 V full to about 1 percent floor, polarity-sensitive
0-10V dimming: Low-voltage control pair that tells the LED driver how to dim, separate from the line voltage
0.083 h: Five minutes expressed in hours, the standard non-voice alarm duration; use 0.25 h for 15 min voice
0U / vertical: A strip mounted in the rear channel that takes no rack-unit space from the 19 in field
0U PDU: Vertical rack power strip mounted in the side channel, taking no rack-unit space [https://anvilfield.com/field-guides/glossary/0u-pdu/]
1.25: Aging and derating margin applied to the summed ampere-hours
1/0 AWG: The minimum conductor size the NEC permits to be paralleled for power, with narrow exceptions
100 percent tie-off: Staying connected to an anchor at all times at height, including during transitions, the core of fall protection
11-month inspection: A full warranty walk before the one-year warranty expires, to catch defects while the contractor still owes the fix
13-week cash forecast: A rolling week-by-week projection of cash in against cash out for the next quarter
150 percent point: At 150 percent of rated flow the pump must produce at least 65 percent of its rated pressure [https://anvilfield.com/field-guides/glossary/150-percent-point/]
19 in rack: The 482.6 mm rail-to-rail mounting width standardized in EIA-310 and IEC 60297 [https://anvilfield.com/field-guides/glossary/19-in-rack/]
1:150 / 1:300 ratio: Square feet of attic floor per square foot of net free vent area required by code
1:48 slope: About 2 percent, the maximum slope in all directions for accessible spaces and aisles
2 AWG: The minimum bare copper conductor size for a ground ring, with heavier sizes common by design
2-pipe / 4-pipe: One coil on a seasonal changeover loop, versus separate heating and cooling coils available at once
2/10 net 30: A supplier term: 2 percent off for paying in 10 days, or the full amount due at 30 [https://anvilfield.com/field-guides/glossary/2-10-net-30/]
24/7 CFE: Carbon-free energy matched to consumption every hour, not averaged annually
25 percent of LEL: The 1 percent hydrogen by volume ceiling the codes commonly hold the room below
25 percent rule: The trigger to pump when grease plus solids reach 25 percent of the liquid depth
25 sync-check: ANSI device 25, the permissive relay that only allows a close when sync conditions are met
27: Cubic feet in one cubic yard, the divisor that takes the volume to orderable units
2N / N+1: Redundancy levels on the critical power and cooling path, full duplicate versus one spare unit
2N / system-plus-system / dual-bus: Two complete independent systems, each a full N, kept apart
3-2-1 rule: Three copies, two media, one offsite; extended to 3-2-1-1-0 with an immutable copy and tested restores
3-pole / 4-pole: Solid neutral switched through, or neutral switched with the phases, which sets the generator grounding [https://anvilfield.com/field-guides/glossary/3-pole-4-pole/]
3-pole vs 4-pole switch: 3-pole switches the phases and leaves the neutral solid (not SDS); 4-pole switches the neutral too (SDS). The single-phase equivalent is 2-pole versus 3-pole
32 reverse power: ANSI device 32, which trips a set that is motoring, drawing power from the bus instead of supplying it
4 to 1 ratio: Extension ladder base set out 1 ft for every 4 ft of working height, about a 75 degree angle
4-bolt rule: 1926.755 requirement that each column be anchored by a minimum of four anchor rods (anchor bolts), with a 300 lb eccentric-load strength criterion
4-inch sphere rule: No opening in a required guard may pass a 4-inch sphere; 6-inch at the stair tread-riser triangle
40 CFR 280: The federal EPA technical standards for underground storage tanks, adopted and enforced through state UST programs
40 percent depth: Where you drill on a slab drying from one side; 20 percent if it dries from two sides
400G / 800G ZR: OIF-defined coherent pluggables for amplified single-span DWDM, targeting roughly 80 to 120 km metro DCI; ZR+ variants extend the reach
450.3: The NEC transformer overcurrent rule, sized off the transformer current, not the conductor
4D / 5D: 4D ties the model to the construction schedule for sequencing; 5D ties it to quantities and cost
4PPoE: Four-pair PoE, the 802.3bt method that uses all four pairs for Type 3 and Type 4 power
4X / corrosion-resistant: Type 4 plus a corrosion-rated material such as stainless, fiberglass, or polycarbonate
5 lb electrode (2.27 kg): The defined-weight cylindrical probe STM7.1 uses; its contact pressure is part of the method
500: Constant for water, roughly 8.33 BTU/gal/degF times 60 minutes per hour
500 psi (freeze threshold): The commonly cited compressive strength fresh concrete should reach before it freezes, so ice no longer ruptures the paste
62 percent rule: The potential pin position, about 62 percent of the way to the current pin, where the reading is valid [https://anvilfield.com/field-guides/glossary/62-percent-rule/]
70V distributed audio: Constant-voltage speaker distribution where transformer taps set each speaker's power, used for many speakers over long runs
8 in flashing height: The commonly cited NRCA minimum height base flashing turns up above the finished roof, higher in heavy snow
8.33: BTU to raise one gallon of water 1 degree F, since a gallon weighs 8.33 lb at a specific heat of 1.0
80 percent fill / OPD: Filling to 80 percent by liquid for expansion room, enforced by the overfill prevention device
811 / one-call: The three-digit number and the center that notify utilities to mark their lines before you dig
811 locate / damage prevention: The one-call system and the law requiring utilities to be located and marked before any dig
90-day retention: Share of new hires still employed at 90 days; a read on whether onboarding works
95 / 99 / 100: Particulate filter efficiency in percent; 100 is HEPA-grade at 99.97 percent
96.25: The constant converting GPM over square feet to inches per hour; one GPM on one square foot is 96.25 in/hr