Construction and demolition debris; separated at the source for diversion and recycling, with regulated material kept on its own manifested path.In: Interior demolition strip-out
Change-advisory board, the group that reviews and approves planned changesIn: Data center MOP SOP EOP
Cabinet ventilation / gas pooling
Vent openings that let leaked gas escape the enclosure; without them gas pools and can reach an explosive concentrationIn: Outdoor kitchen construction guide
Cabinet width / depth
The enclosure footprint, commonly 600 or 800 mm wide and 1000 to 1200 mm deepIn: Rack readiness field guide
Cable fault
A break or disconnection in the sensing cable, reported separately from a leak by a supervised systemIn: Leak detection commissioning
Cable rail deflection
The bowing of a tensioned cable under load that opens the gap, controlled by spacing, tension, and intermediate postsIn: Metal railing and guardrail fabrication
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 fromIn: TIA-606 labeling and administration
Cable tray
A rigid support system that carries cables and conductors along a route in the open, governed by NEC Article 392In: Cable tray field guide
CAC
Cold-aisle containment, which encloses the cold supply aisle and lets the surrounding room run warmIn: Aisle containment QA
CAC (cost to acquire a customer)
Channel spend divided by the jobs it actually booked; the number that matters more than CPLIn: Lead generation and marketing
Cadence
The fixed rhythm of a recurring meeting, such as daily, weekly, or monthly, held at the same timeIn: Progress meetings field guide
A cabinet is a single enclosure; a cage is a fenced private area on the shared floor; a suite is a dedicated roomIn: Colocation fit-out field guide
Calibrated torque tool
A torque wrench or screwdriver, click or dial type, that reads a known torque value and carries a current calibration certificateIn: Termination torque QA field guide
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.In: Warranty reserve and cost management guide
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.In: Excavation shoring field guide
A multi-year forecast of roof actions and costs across the portfolioIn: Roof asset management
Capital reserve
Money set aside on a schedule to fund the replacements the plan forecasts; a sinking fund for the roofsIn: Roof asset management
Capping
Making the cylinder ends plane and square before the break, by bonded sulfur caps (ASTM C617) or unbonded pads (ASTM C1231)In: Strength cylinders and acceptance
The IGBT switching rate, commonly 2 to 16 kHz, trading motor noise against drive heat and bearing currentIn: VFD install and commissioning
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 wallIn: Fixture carriers and supports guide
The pipe lining the hole plus the grout sealing the annulus, which stops surface contamination from running down into the aquiferIn: Water well drilling and well systems
The most contaminated water-restoration category, including sewage, grossly contaminated and carrying bacteria, viruses, and parasitesIn: Biohazard and trauma cleanup guide
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 buffersIn: Elevator modernization and maintenance
Sacrificial-anode or impressed-current protection that stops buried steel from rusting, tested to about negative 850 millivoltsIn: Fuel storage tank field guide
An electrical method that makes a metal structure the cathode of a circuit so it stops corroding and an anode corrodes insteadIn: Cathodic protection field guide
Constant air volume (fixed airflow, varied temperature) and variable air volume (fixed cold supply temperature, varied airflow)In: VAV vs CAV air distribution
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 energyIn: Lab fume hood exhaust guide
Cavity wall is two wythes with a drained air space; veneer is a non-structural skin on a separate backupIn: Masonry construction
CBA
Collective bargaining agreement, the union contract that governs wages, fringe, overtime, and travel on a union jobIn: Hours, overtime, and per diem proof
Chemistry coefficient, 1.0 for common cement types without retarders, higher for retarded or heavily blended mixes; verify against ACI 347In: Formwork, shoring, and reshoring
Construction change directive (AIA G714); directs the contractor to proceed with a change before cost and time are agreedIn: Document control field guide
CCID
Charging-circuit interrupting device, the EVSE's built-in ground-fault protection, commonly tripping at 20 mAIn: EVSE install and commissioning
CCS / NACS (J3400)
The two dominant North American DC connectors; CCS is the Combined Charging System, NACS is SAE J3400In: DC fast charging station design
Common data environment: the single cloud source of truth for the models and data, with version control so everyone is on the current modelIn: BIM VDC coordination
Cell is the hollow core that takes grout and rebar; web is the cross wall between cellsIn: CMU block wall construction
Cell tower / cell site
The structure and the equipment that radiate and connect a wireless cell: tower, antennas, radios, cable, grounding, and shelterIn: Cell tower and antenna install
Cellular / foamed concrete
Low-density concrete made with engineered air from a foaming agent rather than aggregateIn: Lightweight concrete
Cellular vs public-safety DAS
Cellular carries carrier phone signal as a service; public-safety carries responder radio as a code-mandated life-safety systemIn: DAS and public-safety radio
Central inverter / central battery
One UL 924 system feeding the emergency lighting circuits from a single battery bankIn: Emergency and egress lighting
Central station
The staffed, often UL-listed station that receives signals, verifies them, and dispatches per the call listIn: Intrusion alarm field guide
Central UPS
The large uninterruptible power supply in the electrical room, the centralized alternative to distributed rack BBUsIn: Rack BBU and ride-through
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.In: Ceramic and porcelain tile installation
The individual trained and credentialed to direct lead-safe work, and the EPA- or state-certified company; both are required on a covered jobIn: Lead-safe renovation (RRP)
A Compressed Gas Association standard outlet, sized and threaded by gas, that prevents the wrong regulator hookupIn: Compressed gas cylinder safety
CGP / NPDES
The Construction General Permit under the National Pollutant Discharge Elimination System, the permit that authorizes and conditions the stormwater dischargeIn: Erosion control and SWPPP
The thicker wall or service space that hides the carrier, the waste fitting, and the supplies, and provides service accessIn: Fixture carriers and supports guide
Chassis
The sealed working unit (compressor, coils, fans, heat) that slides into the sleeve and gets swappedIn: PTAC and PTHP field guide
Checkpoint
A saved snapshot of the model and optimizer state, written periodically so a failed job restarts from it instead of zeroIn: AI storage tier architecture
Chemical stabilization
Binding pulverized FDR material with cement, lime, fly ash, kiln dust, or a chemical agentIn: Asphalt recycling and FDR
Chilled water / CHW
Cooling where a central chiller makes cold water that is pumped to coils in air handlers and fan coilsIn: Chilled water vs DX cooling
A vertical zone of clean, free-draining stone behind a wall that carries water down to the base pipeIn: Hardscape drainage
Chip seal / BST
Sprayed asphalt binder with cover aggregate rolled in; a bituminous surface treatment or seal coatIn: Chip seal surface treatment
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-surfacingIn: Pavement preservation treatments
Chloramines
Combined-chlorine compounds that off-gas from the water, sting eyes and airways, corrode metal, and are heavier than airIn: Natatorium HVAC field guide
Chloride threshold
The chloride level at the steel above which the passive film breaks down and corrosion startsIn: Rebar corrosion protection
Chloride-induced corrosion
Corrosion of reinforcing steel after chloride from road salt crosses a threshold at the bar and breaks its passive filmIn: Parking structure restoration
The thin finer open-graded stone that bridges the gaps and levels the surface without plugging the reservoir voidsIn: Permeable pavement install
Choke / stonewall
The high-flow limit on the map where gas reaches sonic velocity and flow cannot increase; rarely reached in chiller serviceIn: Centrifugal chiller surge control
Choker / top course
The thin layer of fine material (DG or stone dust) screeded over the base so the turf rests on a tight planeIn: Artificial turf installation
Choker layer
A thin coarse-sand layer between the rootzone and gravel that stops the sand washing downIn: Sports field construction
The pump running against a closed discharge with no flow, reading its highest pressure; capped at 140 percent of rated pressureIn: Fire pump acceptance test
Churn (shutoff)
The no-flow condition where the pressure is highest, held to no more than 140 percent of ratedIn: Fire pump and standpipe guide
One vent serving a battery of 2 to 8 fixtures on a horizontal branch, used for rows of like fixturesIn: Wet venting and common vent guide
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 packetIn: Optical circuit switch and photonics
Circular mil (cmil)
Cross-sectional area unit used to take the proportional 250.122(B) increase when phase conductors are upsizedIn: EGC sizing (NEC 250.122)
Circular-mil area
The conductor's cross-sectional area; paralleled conductors of a phase must match itIn: Parallel conductors, NEC
CISCA class
A spec's design concentrated load and the companion rolling, deflection, set, ultimate, and pedestal values; the values are manufacturer and spec specificIn: Raised floor load rating test
The material type (I gas, II dust, III fibers), the likelihood (Div 1 normal, Div 2 abnormal), and the specific material familyIn: Hazardous classified locations
A graded crushed-aggregate base, fines to about 3/4 in, that compacts into a stable, draining foundationIn: Artificial turf installation
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 enterpriseIn: TIA-606 labeling and administration
Clay tile is fired earth with color baked through; concrete tile is molded sand, cement, and pigment, usually heavier and prone to fadeIn: Tile roof installation
The RRP cleanup endpoint: a damp white cloth wiped on surfaces and compared to the EPA verification card, distinct from lab dust-wipe clearanceIn: Lead-safe renovation (RRP)
The gap from the siding to soil, roof, or deck, commonly about 6 in to grade, that keeps the cut edges off the wetIn: Siding installation
Clearing time
The time from the start of an arcing fault to the device opening and starving the arc; the variable every method shortensIn: Arc energy reduction methods
Clearinghouse
The FMCSA database of CDL drug-and-alcohol testing violations, with pre-employment and annual query dutiesIn: DOT compliance for contractors
Cleave angle
Angle of the cleaved end face from perpendicular; target under about 0.5 degreesIn: Fiber splice loss budget
The code map that ties vapor retarder class and placement to the climate; Zones 6A, 7, and 8 are where NRCA flags vapor retardersIn: Roof vapor retarder and air barrier
Clip spacing
The distance between clips, tightened at corners and edges for wind upliftIn: Standing seam metal roof
Make-before-break transfer, with a brief source overlap and no interruption to the loadIn: ATS commissioning field guide
Closed-cell foam
Foam with sealed cells, giving low water absorption, strength, and about 6 to 7 R per inchIn: SPF roof field guide
Closeout
The whole handoff: punch correction, documentation, training, warranties, spares, and the commissioning record turned over to the ownerIn: Punch list and closeout
Closeout package
The set of records and certifications delivered at closeout: as-builts, O&M manuals, warranties, releases, and certificatesIn: Closeout and warranty management
Closet flange
The fitting that connects the toilet to the drain, set on top of the finished floor to seat the wax ring or gasketIn: Fixture rough-in and setting guide
Cloud / plugging / pour point
Temperatures where wax clouds the fuel, plugs the filter, and stops the fuel flowing, in that order as it coolsIn: Generator fuel system and day tank
Cluster commissioning
Bring-up and proof of the GPU cluster: rack, fabric, GPU, and software, after the facility is commissionedIn: AI cluster commissioning
Communications plenum cable, listed for ducts, plenums, and environmental-air spaces, tested to the NFPA 262 plenum flame testIn: Cabling pathways and firestop
CMU
Concrete masonry unit, the precast concrete block; nominal 8 by 8 by 16, actual 7 5/8 by 7 5/8 by 15 5/8In: CMU block wall construction
CMV
Commercial motor vehicle, generally a vehicle or combination at 10,001 lb or more in interstate commerce, or carrying hazmat or 16-plus passengersIn: DOT compliance for contractors
Optical engines integrated in the switch or NIC package next to the ASIC, instead of pluggable modules, for lower powerIn: Optical circuit switch and photonics
CO/ALR
Copper-aluminum revised, the listing for 15 and 20 A receptacles and switches rated for direct aluminum connectionIn: Aluminum branch wiring
Carbon dioxide stands in for outdoor air per person, because exhaled CO2 builds up when ventilation cannot keep pace with occupancyIn: IAQ monitoring and sensors field guide
CO2 differential
Indoor CO2 above outdoor CO2, the value that tracks per-person ventilation, not a fixed 1000 ppmIn: Economizer and DCV field guide
Coagulation / flocculation
Coagulation neutralizes the charge on fine particles so they can stick; flocculation gently mixes them into settleable flocIn: Treatment plant systems field guide
COBie / structured data
A non-proprietary format for delivering equipment and asset data at handover in a form software can readIn: Digital twin for operations
The 200 lbf load applied at any point on the top in any direction, plus a 50 plf uniform load, checked separatelyIn: Metal railing and guardrail fabrication
CODIT / sealing
Compartmentalization of decay in trees, the tree walling off a wound rather than healing it backIn: Tree pruning and maintenance
Codominant stem / included bark
Two near-equal stems in a tight union with bark trapped inside it, a weak fork prone to splittingIn: Tree pruning and maintenance
Codominant stems
Two or more stems of nearly equal size from one point, with no single dominant leaderIn: Tree cabling and bracing
Codominant stems / included bark
Two equal stems from one point with bark turned inward at the union, a built-in weak plane prone to splittingIn: Tree risk assessment
CODS
Critical operations data system, the 645 path that can omit the EPO under documented, supervised, AHJ-approved conditionsIn: EPO testing field guide
Coefficient of thermal expansion (α)
How much a material grows per unit length per degree of temperature changeIn: Pipe thermal expansion
Optics that encode data in the light's amplitude and phase and use receiver DSP to recover it and compensate dispersion over distanceIn: Data center interconnect (DCI)
Placing and protecting concrete when the air is at or expected below about 40 F during the protection period, per ACI 306In: Cold weather concreting
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 loopIn: Liquid cooling loop chemistry
Cold-shrink
A pre-expanded rubber termination that contracts onto the cable under its own tension when the core is pulled, with no heatIn: MV cable termination and testing
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 torchIn: MV termination and splicing
Cold-water sandwich
The cool slug between two hot draws on a tankless while the burner re-firesIn: Water heater types
Coliform
Indicator bacteria common in soil and gut; their absence is the accepted sign the line is microbiologically safeIn: Potable water disinfection guide
Collective / NCCL
Group communication across GPUs such as all-reduce; NCCL is the common library whose bandwidth tests prove itIn: AI cluster commissioning
Colocation
Leasing space and power in someone else's facility, priced in dollars per kilowatt per monthIn: Data center TCO cost model
An oversized, shallow-slope horizontal drain that vents itself, used for island sinks, sinks, lavatories, and floor drainsIn: Wet venting and common vent guide
Combination-type AFCI
An AFCI that detects both series arcs and parallel arcs, the type the code generally requiresIn: GFCI and AFCI protection
The manufacturer-required distance from a grill or burner to combustible construction, held with a non-combustible enclosureIn: Outdoor kitchen construction guide
Combustible scrap
Burnable debris such as packaging, sawdust, and felt that has to be cleared at regular intervalsIn: Jobsite housekeeping
Combustibles
Materials that can ignite and burn, cleared within about 35 ft of the work or covered with fire-resistant blankets and shieldsIn: Hot work permit field guide
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 combustionIn: Combustion analysis field guide
Combustion analyzer
Reads flue-gas O2, CO, and temperature and calculates efficiency and CO air-free for gas-fired equipmentIn: HVAC test instruments field guide
Comfort / crossover valve
A thermostatic valve bridging hot to cold under the far fixture in a return-less retrofitIn: Hot water recirculation loops
Commercial ice machine
A refrigeration system that freezes potable water into cube, nugget, or flake ice for food service, healthcare, and industryIn: Commercial ice machine field guide
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 NSFIn: Kitchen equipment install field guide
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 dutyIn: Commercial refrigeration field guide
The competent person spots and corrects hazards and inspects the rig; the qualified person designs the rigging and anchorsIn: Suspended scaffold and swing stage safety
A slab poured on corrugated steel decking; the steel pan reflects the radar and hides what is at or below itIn: Concrete scanning before you drill
Compound gauge
The manifold's low-side gauge; its vacuum scale stops near 30 in Hg, far short of the micron rangeIn: Refrigerant evacuation field guide
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 shellIn: Compressed gas cylinder safety
Compression tank
The older plain-steel tank with air and water in direct contact, which waterlogs over time and is drained to rechargeIn: Expansion tank and air field guide
Compressive strength
Resistance to crushing under load, in psi, the cover board's protection against point loadsIn: Roof insulation and cover board
Concealed damage
Damage found after delivery with no external sign at the dock; the hardest freight claim to winIn: Switchgear receiving inspection
Concealed work
Buried or hidden work that can only be recorded before cover-up, after which the as-built is the only recordIn: As-built record drawings
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 floorIn: Fixture carriers and supports guide
Weight delivered through a small contact area, such as a rack foot or caster, checked separately from the uniform loadIn: Structural design for AI racks
The coil or heat exchanger where the vapor gives up its latent heat and condenses back to liquid, rejecting heat to facility waterIn: Two-phase cooling
A furnace, boiler, or water heater that condenses flue-gas vapor to recover latent heat, making acidic condensateIn: Condensate neutralizer field guide
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 sidesIn: Working clearance (110.26)
Condition monitoring
Measuring a machine's vibration, heat, oil, or sound to assess its health while it runsIn: Predictive maintenance guide
The vertical storm pipe carrying flow from a roof drain or scupper down through the building; conductor inside, leader often outsideIn: Interior storm drainage piping sizing
Conductor fill
The summed area of all conductors as a fraction of the trough's interior area, held to 20 percentIn: Wireway and gutter field guide
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 gapIn: Interior storm drainage piping sizing
Conductor head / leader head
The open collector box at the top of a downspout that catches and funnels flow and spills overflowIn: Gutters and downspouts
Conductor insulation
The cloth and rubber covering on the wire, distinct from attic thermal insulationIn: Knob and tube wiring
Conductors per phase
How many conductors share one phase, equal to the number of parallel setsIn: Parallel conductors, NEC
A compound-filled fitting that blocks gas, vapor, and flame from traveling through the conduit between enclosures or across the boundaryIn: Hazardous classified locations
A site instrumented with internet-connected sensors on people, equipment, materials, and the environment, feeding data to a platformIn: Connected jobsite and RTLS
Anything that must be in place before a task can be done: material, information, predecessor work, labor, equipment, space, or external itemsIn: Lean construction field guide
Constructability
Whether the design can actually be built and sequenced, reviewed on paper before the conflicts reach the field.In: Preconstruction field guide
Transferring the design points, lines, and elevations from the drawings or model onto the ground and structure so each trade builds in the right placeIn: Construction layout
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 tradeIn: Construction robotics
Construction wind speed
The reduced wind the temporary bracing is designed to, lower than the building's final design windIn: Tilt-up bracing and erection
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 hazardIn: Water service and meter tap guide
Containment vs isolation
Protection at the service to guard the public main versus protection at each fixture to guard the buildingIn: Cross-connection control
Continuous means the inspector observes the full time work is performed; periodic means part-time or at intervals, as the code tables and statement assignIn: Data center structural QA
The surveyed set of reference points, control points for horizontal position and benchmarks for vertical, that everything is laid out fromIn: Construction layout
Control stop
The angle stop at the supply that shuts off and trims flow to the valve; not the volume adjustment.In: Flushometer flush valve types
Control vs expansion joint
Control joint relieves CMU shrinkage; expansion joint relieves clay brick growthIn: Masonry construction
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 controlsIn: Steel erection and connections
Machinery that moves product through a building, the broad trade covering belt, roller, chain, screw, pneumatic, overhead, and sortationIn: Conveyor system installation
Cool-season annuals bloom in mild weather and decline in heat; warm-season annuals need warm soil and air and die at frostIn: Seasonal color and annual rotation
Prefabricated mechanical plant: chillers, pumps, heat rejection, and coolant distributionIn: Modular data center deployment
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 toleranceIn: Coordination study field guide
Valves at the service ports that let you isolate the system from the pump and hoses to run an honest decay testIn: HVAC test instruments field guide
Core-removal tool
A valve that lets you take out the Schrader cores while the system stays sealed, removing a major flow restrictionIn: Refrigerant evacuation field guide
Cores
Cut samples through the roof that confirm wet versus dry and verify survey readingsIn: Reroof: recover vs tear-off
Corner bead
Metal, paper-faced, or vinyl reinforcement that straightens and protects an outside corner and gives a hard line to finish toIn: Drywall and gypsum board finishing
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 serviceIn: Water service and meter tap guide
The relationship between ICMV and core density built on a test section, reported as a coefficient, that lets the ICMV map be read with confidenceIn: Intelligent compaction for asphalt
Corrosion control
Utility treatment, often orthophosphate, that coats lead pipe to limit how much lead dissolvesIn: Lead service line guide
Prevention plus appraisal (conformance) against internal plus external failure (rework and callbacks); failure cost dwarfs preventionIn: Construction QA/QC program
Cost per MW
Build cost per megawatt of IT capacity, the headline metric; varies widely by market and timeIn: Data center TCO cost model
Cost to complete
An honest estimate of what it will take to finish the remaining work, not what is left in the budgetIn: Construction cash flow and WIP
Change of value, logging or reporting a point only when it moves past a threshold rather than on a fixed intervalIn: BMS and DDC controls commissioning
Cove / detail
The membrane turned up at a wall or curb over a fillet, plus the reinforced treatment at drains, penetrations, and terminationsIn: Traffic deck coating
Cover
The depth of concrete from the surface to the reinforcing steel, which protects the bar and sets a shallow anchor's clearanceIn: Concrete scanning before you drill
The dense board over the insulation that protects the membrane and gives it a bondable baseIn: Roof insulation and cover board
Coverage / yield
Roof area one gallon covers at a target thickness; theoretical is 1604 times solids over DFT milsIn: Roof coating mils and yield
Coverage grid / DAQ
The floor divided into squares and measured for signal level and quality; DAQ is delivered audio quality, how clearly voice is understoodIn: DAS and public-safety radio
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 factorIn: Construction labor productivity tracking
CPI / coalescing plate
Corrugated-plate separator whose inclined plates merge small oil droplets for better effluent in a smaller tankIn: Oil/water separator field guide
Critical path method: a schedule of logic-linked activities whose dates and critical path the software calculates from the relationships and durationsIn: Construction scheduling field guide
CPR
Cardiopulmonary resuscitation: chest compressions, with or without rescue breaths, to keep blood movingIn: Electrical shock first aid
CPSI
Certified Playground Safety Inspector, the NRPA credential for auditing a playground against CPSC and ASTM standardsIn: Playground safety surfacing
CPT
Control power transformer, steps line voltage down to feed the control circuit, with primary and secondary fusingIn: MCC commissioning
CPT / SPT verification
Cone penetration and standard penetration tests run before and after treatment to confirm the soil actually improvedIn: Ground improvement and grouting
Computer room air handler (chilled water coil) or air conditioner (DX with a compressor); in-row units come in both formsIn: In-row cooling commissioning
Crazing
A shallow random map of hairline cracks under about 1/8 in deep; cosmetic, from fast surface dryingIn: Concrete surface defects diagnosis
CRCP
Continuously reinforced concrete pavement; heavy continuous steel, no transverse contraction jointsIn: Concrete pavement types
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 controllerIn: Access control system field guide
The power, cooling, and supporting systems whose failure stops the load, and the people and program that keep them runningIn: Data center staffing and workforce
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.In: Data center operations and the NOC
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 heightIn: Playground safety surfacing
Critical lift
A lift with extra consequence or less margin, near capacity, multi-crane, or over occupied space, needing added planningIn: Crane and rigging safety
The worst-case box driving the reset, the one needing the most static or coldest air at any momentIn: VAV box commissioning field guide
Critical-environment mindset
The discipline to follow procedure, treat systems as live, and value not making it worse over working fastIn: Data center staffing and workforce
Criticality / RCM
Ranking assets by consequence and likelihood of failure; reliability-centered maintenance assigns the strategy per failure modeIn: Predictive maintenance guide
CRM
Customer relationship management; the system and practice of keeping the single organized record of every customer and interactionIn: Customer database and CRM
A physical cable joining two circuits patch field to patch field, the manageable interconnection model and the unit the record tracksIn: Cross-connect patch records
Primary amps to secondary output, such as 100:5 or 200 A to 333 mV, set in the meter to match the CTIn: Submetering and energy monitoring
CU
Coefficient of utilization, fraction of source lumens reaching the work plane, from the photometric tableIn: Commercial lighting design
CU/AL
The marking on breakers and larger equipment terminals; not a rating for standard aluminum branch devicesIn: Aluminum branch wiring
Cube / nugget / flake
Hard clear ice for drinks; soft chewable pellets for fast food and healthcare; soft shaved layers for display and medicalIn: Commercial ice machine field guide
Design signals like a mowed edge or signage that show a native planting is intentional, not neglectedIn: Native and pollinator planting
CUI
Corrosion under insulation, the hidden rust of a pipe held wet beneath failed insulation or jacketIn: Pipe insulation field guide
Cultural control
Changing mowing, watering, fertility, or variety so site conditions no longer favor the pestIn: Landscape IPM field guide
Cumulative sampling
The effect by which many sampling holes pull from the mixed room air at once, the reason ASD works in high airflowIn: Aspirating smoke detection
Cupric oxide scale
Black flaky copper-oxide formed inside the pipe when copper is brazed with oxygen present; breaks loose and plugs the systemIn: Refrigerant line brazing field guide
The utility's shutoff valve at the property line and the access pipe over it operated from the surface with a curb keyIn: Water service and meter tap guide
Protective current per unit of bare steel area; set by coating quality and soil resistivity, and the basis for sizingIn: Cathodic protection field guide
Current-carrying conductor
A conductor counted for derating, the count that triggers ampacity adjustment when it crosses the thresholdIn: Wireway and gutter field guide
A fuse that interrupts within the first half-cycle of a high fault, limiting let-through energy and clearing the arc fastIn: Arc energy reduction methods
Curtailment
Cutting the site's grid draw on the grid's worst days, often under a program or interruptible tariffIn: Data center grid flexibility
Curtain wall
A non-structural aluminum-and-glass building skin hung off the structure, carrying only its own weight and wind.In: Curtain wall and glazing
The full revenue a customer generates across every job and referral, not just the first ticketIn: Customer database and CRM
Customer lifetime value (LTV)
The total profit a customer produces over the whole time they do business with you, including fees, pull-through, and replacementIn: Service agreements and recurring revenue