Radon and vapor-intrusion mitigation field guide for slabs

Radon and vapor-intrusion mitigation, and the air coming up through the floor

Radon and vapor-intrusion mitigation is the set of methods that keeps soil gas from being pulled up through the slab and the foundation into the building, where it accumulates and people breathe it. The air under a slab is not still and clean. It carries gas from the soil, and the building tends to pull that air up through every crack, joint, and penetration in the floor.

Two gases drive the work. Radon is a radioactive gas from the natural decay of uranium in soil and rock, and it is a leading cause of lung cancer. Volatile organic compounds, the VOC vapors that rise off contaminated soil or groundwater, are the other, and they show up on sites with a petroleum or solvent history. Both move the same way. The building runs at a slight negative pressure relative to the soil, and that pressure difference draws soil gas indoors.

The fix is not a coat of something. You depressurize the soil under the slab so the gas vents outside through a pipe instead of being pulled inside, using a gas-permeable layer to spread the suction, a vapor barrier over the soil, a vent pipe, and a fan, with the obvious entry routes sealed to help the suction hold. The only proof any of it worked is a measurement. This sits next to two related problems. Below-grade waterproofing keeps liquid water out, covered in the below-grade waterproofing guide, and the vapor retarder under a new slab is part of the slab-on-grade guide. Soil-gas mitigation overlaps both and is its own job.

Why the soil gas is the biggest hazard in the building

Radon is the second leading cause of lung cancer behind smoking, by the accounting EPA and the surgeon general use, and the first cause among people who never smoked. That is the reason this work matters more than any finish or detail you will touch on the same building. You cannot see it, smell it, or taste it, and the dose is cumulative over years of breathing it.

The mechanism is plain. Soil gas sits under pressure in the ground. The building, warmed and exhausted by its own systems, runs slightly negative against that soil, so it acts like a weak vacuum on the floor and pulls the gas up through anything open. A slab is not airtight. It has shrinkage cracks, the joint where it meets the wall, plumbing and conduit penetrations, and often an open sump. Every one of those is a path.

On a contaminated site the same physics carries industrial vapor into the building, which is the vapor-intrusion problem the environmental side worries about. Treat the levels, the methods, and the testing as governed by EPA, the ANSI/AARST standards, the state radon or environmental program, and the authority having jurisdiction. The hazard is real and the numbers are not yours to set.

What the soil gas actually is

Radon comes from uranium. Uranium decays through radium to radon, a colorless inert gas, and because it is a gas it migrates out of the soil grains and through the pore spaces toward the surface. Under an open field it dilutes into the air and means little. Under a slab it has nowhere to go but up through the floor, so it concentrates indoors. Radon then decays further into solid particles that lodge in the lungs, which is where the dose comes from.

VOC vapors are a different source with the same delivery. On a site with contaminated soil or groundwater, chemicals like chlorinated solvents (think the dry-cleaner and degreaser family, TCE and PCE) or petroleum hydrocarbons off a leaking tank give off vapor that rises through the same soil-gas pathway. Petroleum vapors tend to biodegrade as they move up through aerobic soil. Chlorinated solvents generally do not, so they travel farther and are the more stubborn vapor-intrusion problem.

The distinction matters for who is involved. Radon is a natural hazard handled under the radon programs. Vapor intrusion from contamination is an environmental-cleanup matter, often with a consultant and a regulator on the site, and the screening levels and methods come from EPA and ITRC guidance, not the radon action level alone. Confirm which problem you have before you design for it.

How soil gas gets into the building

The building pulls it in. Three drivers stack up. The stack effect, warm air rising and leaving high in the building, pulls makeup air in low, including through the floor. Exhaust fans, dryers, and combustion appliances pull air out and the soil helps replace it. Wind loads one side of the building and unloads another. The net result through much of the year is a floor under slight negative pressure relative to the soil beneath it.

Give that pressure a path and it takes it. The common routes are shrinkage and settlement cracks in the slab, the perimeter joint where the slab meets the foundation wall (the cold joint that is rarely tight), penetrations for plumbing, conduit, and floor drains, the open or loosely covered sump pit, and porous block walls below grade that breathe through their cores. Crawl spaces with bare soil or an unsealed liner are a wide-open path.

This is why sealing alone never solves it. You can chase and caulk every crack you find and the building will keep pulling gas through the ones you did not find, through the slab itself, and through the block. Sealing reduces the leakage. It does not reverse the pressure that drives the gas in. Reversing that pressure is the whole point of the next section.

What is sub-slab depressurization?

Sub-slab depressurization, SSD, is the primary method for radon and soil-gas mitigation, and it is the one that actually works. A fan draws a vacuum in the soil and aggregate under the slab, so the pressure under the floor is lower than the pressure in the building above it. The gas follows the lower pressure into a pipe and out above the roof instead of being pulled up into the rooms. You are not blocking the gas. You are giving it an easier exit than the floor.

The standards-of-practice from ANSI/AARST and the EPA guidance treat active SSD as the default for most buildings because it is the only approach that consistently drives radon well below the action level. Active soil depressurization commonly cuts indoor radon by 80 to 99 percent, with a starting level near 4 pCi/L often dropping to under 1.5 pCi/L after a working system goes in.

The reason it beats sealing is the pressure. SSD inverts the pressure difference at the slab. Once the soil under the floor is more negative than the room, the small openings that used to admit gas now leak a trickle of room air downward into the system, which is harmless. Seal those openings and you make the fan's job easier, but the fan is doing the work. Treat sealing as support for SSD, never as a substitute for it.

The suction field under the slab

A working SSD system depends on the suction reaching the whole footprint of the slab, not just the soil right under the pipe. That zone of measurable vacuum is the suction field, and confirming it is the difference between a system that reads good on the manometer and one that actually lowers radon.

The gas-permeable layer is what spreads it. Clean coarse aggregate under the slab lets the vacuum extend out from the suction point for many feet in every direction. Where there is no aggregate, just tight native soil or fill, the field collapses to a small zone and a single suction point may not reach the far corners. That is when a system reads suction at the pipe and still fails the post-mitigation test.

Pros prove the field with a communication test, also called pressure field extension or a sub-slab pressure test. You drill a few small test holes through the slab away from the suction point, run a fan or a shop vacuum on the suction pit, and read the vacuum at each hole with a micromanometer. Chemical smoke at a crack shows whether air is being pulled down. If the far holes show no measurable pull, you add a suction point or relocate, because no communication means no coverage no matter what the main gauge says. Confirm the diagnostic method and the acceptance against the AARST standard and the AHJ.

Passive versus active systems

A passive system is a vent stack with no fan. It runs a sealed pipe from the gas-permeable layer up through the warm interior of the building and out the roof, and it relies on the stack effect, the warm pipe drawing upward, to pull soil gas out. An active system adds a fan to that pipe and creates a real, steady vacuum under the slab.

The honest version: passive helps, but it often does not finish the job. Passive systems commonly cut radon by something like 30 to 50 percent, which is real but unreliable, and it varies with weather and the season because the stack effect is weak and inconsistent. Active systems with a fan commonly reach 90 to 99 percent. If a passive system tests above the action level, it goes active. That is not a failure of the design. It is the design working as intended, because radon-resistant new construction is built passive on purpose with the fan ready to add if the test says so.

Plan for the fan even when you build passive. Route the stack so a fan can be added later in an unconditioned space, and provide the power. A passive stack that was run through finished living space leaves no good place for the fan and forces an ugly retrofit when the test comes back high.

The radon fan and the manometer

The fan is what makes the system active, and where it sits is a safety rule, not a preference. The radon fan goes in an unconditioned space, an attic, the garage attic, or outside on an exterior wall, never in the living space or a basement. The reason is the pipe after the fan is under positive pressure. If that section leaks inside the conditioned space, it pushes the soil gas it just collected back into the building. Keep the fan and all of its positive-pressure pipe out of occupied areas so a leak vents to the outside, not the rooms.

Fans are rated by airflow and the static pressure they can pull, and the right one depends on the soil. Tight soil needs a high-suction fan moving little air. Loose aggregate needs more flow at lower suction. Size it to the sub-slab diagnostics, not by habit, and confirm against the manufacturer and the AARST standard.

Every active system needs a working failure indicator, and the standard is a U-tube manometer plumbed into the pipe. It is a clear tube with liquid in it, and the suction in the pipe offsets the two columns. Uneven columns mean the fan is pulling. Level columns mean the fan has quit or the pipe is blocked, and the occupant is back to breathing soil gas without knowing it. Show the homeowner the gauge and tell them what level columns mean, because that is the only on-site sign the system died.

The vent pipe and where it discharges

The vent pipe carries the soil gas from under the slab to a discharge above the roof, and the routing has two jobs: keep the gas moving up and keep the discharge away from anywhere people breathe. It is typically solid PVC, commonly 3 in or 4 in, run as straight and vertical as the building allows so the fan is not fighting unnecessary friction and so condensate drains back down to the soil instead of pooling.

The discharge point is where amateurs cut corners and where the standard is specific. The pipe terminates above the roof, not at a soffit or a basement window well, and it is held clear of windows, doors, and air intakes so the vented gas does not get pulled straight back inside. The AARST standards-of-practice set the discharge above the roof line, a set height above grade, and a minimum separation from any opening, with the typical figures being roughly 10 ft from or 2 ft above an opening within 10 ft, and above the eave. Confirm the exact clearances against the adopted standard and the AHJ, because the numbers get amended.

A discharge dumped next to a bedroom window is a classic failure. The fan faithfully pulls radon out of the soil and the building draws it right back in through the window a few feet away, and the post-mitigation test never improves. Get the termination right and away from openings, or the rest of the system is wasted.

The gas-permeable layer in new construction

In new construction the cheapest, most reliable place to handle radon is under the slab before it is poured, which is radon-resistant new construction, RRNC. The core of it is a gas-permeable layer: a 4 in bed of clean, coarse aggregate under the slab that lets soil gas, and the suction that collects it, move freely across the whole footprint. EPA's RRNC techniques and the ANSI/AARST new-construction standard build the system around this layer.

That aggregate layer is what makes a single suction point reach the entire slab. With it, one pipe pulls a vacuum across the building. Without it, on tight soil, the suction field shrinks to a small zone and the system struggles, which is exactly the retrofit problem you are trying to design out. Spend the gravel.

RRNC stacks the rest of the system on that layer: the soil-gas retarder over the aggregate, a vent pipe teed into the aggregate and run up through the building and out the roof, sealed entry routes, and electrical roughed in near the pipe for a fan that gets added only if the test calls for it. Built into a new pour the whole package is a small fraction of a retrofit. Skip it and you pay several times more to core a finished slab later.

The vapor and soil-gas retarder under the slab

A vapor and soil-gas retarder is a continuous sheet, commonly polyethylene, laid over the gas-permeable aggregate before the slab is poured. It does two jobs at once. It slows soil gas from passing up through the slab, and it keeps wet concrete from clogging the aggregate during the pour so the gas-permeable layer stays open for the suction. For radon work a 6-mil poly is a common minimum, and heavier sheet is often specified because thin film tears under foot traffic and rebar chairs.

The retarder only works if it is continuous. Lap the seams, seal them, and seal around every penetration, the pipe boots, the plumbing, and the perimeter, or the suction leaks and the gas finds the gaps. A torn or open retarder is the same failure as an unsealed slab. This is also the same membrane the slab-on-grade guide covers for moisture control, so on most jobs one well-detailed sheet serves both the moisture and the soil-gas purpose. Coordinate the spec so you install it once and to the higher standard.

For ordinary radon, poly is enough. On a contaminated site the retarder becomes a chemically resistant vapor-intrusion membrane, which is a heavier specification covered further down. Match the membrane to the gas you are stopping.

Sealing the entry routes

Sealing closes the obvious openings in the floor so the fan does not waste its suction pulling room air down through them. It helps the SSD work, and it is part of every good system. It is not the system. A house sealed tight with no depressurization still pulls radon through the slab and the cracks you missed, because the pressure that drives the gas is still there.

Seal the perimeter joint where the slab meets the wall, the shrinkage and settlement cracks, the gaps around plumbing and conduit penetrations, floor drains where appropriate, and any open block-wall top course below grade. Use a durable flexible sealant rated to move with the crack, commonly polyurethane, not a hard filler that cracks loose the first season. Closing these openings raises the vacuum the fan can hold under the slab and shrinks the airflow it has to move.

The order matters. Seal as support for the SSD, and never sell sealing on its own as radon mitigation. A homeowner who paid to have cracks caulked and was told they were protected is the most common way people end up with a false sense of safety and a radon level that never moved.

The sump as an entry route

An open sump pit is one of the largest soil-gas holes in the building, because it is a direct opening straight into the wet, gas-rich soil and drain tile under the slab. A loose lid does almost nothing. The building pulls air up out of the pit all day.

On a mitigated building the sump gets a sealed, gasketed lid with sealed penetrations for the discharge line and the float wire, and it is often a good location to tie the SSD suction into, because the pit already connects to the sub-slab drain tile that spreads the vacuum. A sealed sump that doubles as the suction point can be an efficient system on a house with a perimeter drain.

Keep the radon work compatible with the sump's day job of moving water. The lid has to stay serviceable, the pump has to breathe and discharge, and any air vent for the pump stays outside the depressurized side. Seal it tight and keep it pumping.

New construction versus retrofit

The same physics, two very different jobs. In new construction you build the system into the slab before the pour, which is RRNC, and it is cheap because the aggregate, the membrane, and the pipe go in while the floor is open and the trades are already there. In an existing building you retrofit, which means coring the finished slab, digging a suction pit, and adding the pipe and fan after the fact.

The cost gap is large and it is the whole argument for building it in. RRNC adds a modest amount to a new house. A retrofit costs several times that and leaves visible pipe and a fan on a finished building. If you have any say at design in a radon-prone area, build the passive system in and rough the fan, every time.

The performance can also differ. New construction gets a clean, continuous gas-permeable layer and a sealed membrane under the whole slab, so the suction field is excellent. A retrofit works with whatever is actually under the existing slab, which might be tight fill with no aggregate, and that is why retrofit design leans on the sub-slab diagnostics to find where the suction will reach. Confirm the new-construction requirements against the ANSI/AARST standard, the adopted building code, and the state radon program, because some jurisdictions and zones now require RRNC.

Installing a retrofit system

A retrofit SSD on an existing slab follows a set sequence. Run the sub-slab diagnostics first to find a suction point that communicates across the slab, using a test hole and a micromanometer, because picking the location blind is how you get a system that reads fine and tests high. Then core the slab at the chosen point.

Dig out a suction pit under the core, a void in the soil or aggregate that lets the vacuum spread out from the pipe rather than choking at a small hole. Set the suction pipe into the pit and seal it to the slab. Route the pipe up to the fan in an unconditioned space and out above the roof. Add the fan, the manometer, and a label that says what the system is and to keep it running. Seal the obvious entry routes, the perimeter joint, the cracks, and the sump.

Then test, and this is the step that closes the job, not the install. A system is not done when the fan spins. It is done when a post-mitigation radon test confirms the level dropped below the action level. If it did not, you go back to diagnostics, add a suction point, or seal more, and you test again. No post-mitigation test, no finished system.

What is vapor intrusion from contamination?

Vapor intrusion is the migration of VOC vapors from contaminated soil or groundwater up into a building through the same soil-gas pathway radon uses. The source is not natural decay. It is a release: a leaking underground tank, an old dry cleaner, an industrial degreaser, a brownfield with a chemical history. The vapors rise off the contaminated soil or the water table and the building's negative pressure pulls them in.

The contaminant changes the math. Petroleum vapors biodegrade as they pass up through aerobic soil, so they often attenuate over a vertical separation. Chlorinated solvents like TCE and PCE generally do not biodegrade on that path, so they travel farther and trigger evaluation at greater distances. Vapor-intrusion guidance commonly flags buildings within about 100 ft of known chlorinated contamination above screening levels for a closer look. Treat those screening distances and levels as set by EPA and ITRC guidance and the state environmental program, not by the radon action level.

Mitigation looks similar to radon SSD, an active sub-slab system that depressurizes the soil and vents it outside, usually paired with a stronger membrane. The differences are the design targets, the chemical resistance of the materials, and the oversight. On a contaminated site a consultant and a regulator are usually driving the cleanup, and the mitigation system is part of a larger remedy. Ignoring vapor intrusion because the building only got tested for radon is a real and expensive mistake on a brownfield.

Vapor-intrusion membranes

On a contaminated site the thin poly that handles radon is not enough, because industrial vapors can attack or pass through ordinary polyethylene and the consequence of a leak is exposure to a known toxin, not just high radon. Vapor-intrusion work uses a heavier, chemically resistant membrane chosen for the specific contaminant.

These come as thick sheet membranes with welded or taped seams or as spray-applied membranes that form a continuous monolithic layer over the prepared subgrade, sometimes with a reinforcing layer and a chemical-resistant core. The selection turns on what is in the soil, because a membrane that resists petroleum may not resist a chlorinated solvent, and the design engineer matches the material to the contaminant. Detailing at penetrations and the perimeter is where these systems pass or fail, the same as any membrane.

The membrane rarely stands alone on a contaminated site. The common design pairs the chemically resistant barrier with an active sub-slab depressurization or venting system underneath it, so the membrane is a barrier and the SSD relieves the pressure and carries vapor away, two defenses instead of one. Specify the membrane and the venting together, and follow the EPA and ITRC vapor-intrusion guidance and the regulator for the site.

Testing is the only proof it works

Nothing about a radon system tells you it worked except a measurement. The fan can spin, the manometer can show suction, the pipe can run clean above the roof, and the indoor radon can still be above the action level because the suction field did not reach where the gas comes in. You test before to know you have a problem, and you test after to prove you fixed it. Skip the post-mitigation test and you do not have a finished job, you have a guess.

Short-term tests run a few days, typically 2 to 7, and are the quick screen. Long-term tests run 90 days or more and give the truer picture because radon swings with weather and season. Continuous radon monitors log readings over a minimum measurement period, commonly at least 48 hours, and let a pro see the hourly pattern and confirm closed-house conditions. For a short-term test the protocol calls for closed-house conditions, windows and exterior doors kept shut except normal entry, starting at least 12 hours before and held through the test, or the result reads artificially low.

Follow the testing protocol from EPA and the ANSI/AARST testing standards and the state radon program, and on a contaminated site follow the EPA and ITRC vapor-intrusion sampling guidance instead, which is a different and more involved protocol. Test before and after, against the action level, every time. That is the part that is not optional.

What is the radon action level?

The radon action level in the United States is 4 pCi/L, the indoor radon concentration at or above which EPA recommends you fix the building. It is picocuries per liter of air, a measure of radioactivity, and 4 pCi/L is the number that triggers mitigation in nearly every program and real-estate transaction in the country.

It is not a safe-versus-unsafe line. EPA is explicit that there is no known safe level of radon, and it recommends that people also consider fixing a building in the 2 to 4 pCi/L range, because the risk does not drop to zero below 4. The World Health Organization references a lower reference level. So 4 pCi/L is the action threshold most programs enforce, not a guarantee that 3.9 is fine.

Treat the number as governed, not chosen. The action level, the disclosure requirements, and any tighter local threshold come from EPA, the state radon program, and the AHJ, and some states and zones set their own rules. Confirm the operative level and the disclosure obligations for the jurisdiction before you advise anyone on a result.

Monitoring and re-testing over time

A radon system is not set-and-forget, because the one part that does the work, the fan, will eventually fail and gives no audible warning when it does. The manometer is the minimum monitor, a passive U-tube that shows at a glance whether the fan is pulling, and the occupant has to actually look at it and know that level liquid means the fan died.

Better installations add an active alarm that sounds or signals on loss of suction, and a continuous radon monitor gives an ongoing reading rather than a snapshot. On schools and large buildings the ANSI/AARST standards lean toward continuous monitoring and documented checks because the stakes and the occupant count are higher.

Re-test on a schedule even when everything looks fine. Radon fans have a service life, soil and drainage conditions change, and renovations can open new entry routes or change the building's pressure. A common recommendation is to re-test every couple of years and after any major work or any change to the heating, cooling, or ventilation. Confirm the monitoring and re-test cadence against the AARST standard and the state program.

Code, disclosure, and the AHJ

Radon requirements are uneven across the country, so the rules depend entirely on where the building is. Some states and some high-radon zones require radon-resistant new construction in the building code, some require disclosure of known radon levels and systems in a real-estate sale, and many leave it to the buyer and seller. There is no single national radon code the way there is a national electrical or building code.

Real-estate disclosure is where most people first meet the issue, because a radon test is a routine part of a home inspection and a high result becomes a negotiation. Mitigators and inspectors operating in a transaction follow the state's testing and disclosure rules, which carry specific protocols for tamper resistance and closed-house conditions during a real-estate test.

On a contaminated site the regulatory path is different again, run through the state environmental program and EPA cleanup oversight rather than the radon program. Confirm what applies, the building-code requirement, the disclosure law, the testing protocol, and the cleanup oversight, against the adopted code edition, the state radon or environmental program, and the AHJ before you rely on any of it.

What to record on the job

The record is what proves the building is protected, and on a radon or vapor-intrusion job it is also a liability document, because someone will rely on it during a sale or a regulatory closeout. Capture the pre-mitigation test result and protocol, the system you installed and where the suction points and the discharge are, the fan model and its rating, the sub-slab diagnostics or communication test results, the post-mitigation test result against the action level, and the date and who tested.

Tie the test results, the system details, and the post-mitigation confirmation to the property in a field tool like FieldOS so the proof travels with the building instead of living on a clipboard that gets lost. A radon system with no documented post-mitigation test is the same problem on paper as a system that was never tested: there is no proof it worked.

Note the discharge location and the manometer baseline reading too. The next person who services the system needs to know what normal suction looked like the day it was commissioned.

Common mistakes

• Relying on sealing alone with no sub-slab depressurization, so the pressure that drives the gas in is never reversed.
• Leaving a passive system passive when the test came back above the action level instead of adding the fan.
• Never running a post-mitigation radon test, so there is no proof the level dropped.
• Putting the fan in the living space or basement, where a leak in the positive-pressure pipe pushes soil gas back inside.
• Discharging the vent too close to a window, door, or air intake, so the building pulls the vented gas right back in.
• Skipping the sub-slab communication test and placing the suction point blind, so the suction field never reaches the entry routes.
• Ignoring vapor intrusion on a contaminated or brownfield site because the building was only screened for radon.

Field checklist

Standards and references

EPA sets the framework for radon: the 4 pCi/L action level, the recommendation to consider fixing between 2 and 4 pCi/L, the radon-resistant new construction techniques, and the Map of Radon Zones that flags higher-potential areas. EPA points to the consensus standards for the actual work.

The ANSI/AARST standards-of-practice are where the methods live. For existing one- and two-family homes, soil-gas and radon mitigation is covered by the standard commonly known as SGM-SF, which addresses radon and other hazardous soil gases. Schools and large buildings are covered by RMS-LB and the consolidated SGM-MFLB for multifamily, school, and commercial buildings. New construction is covered by the rough-in and control standards, commonly CCAH for dwellings and CC-1000 for larger buildings, and there are separate AARST testing standards for measurement. The exact designations and editions change as the standards are revised and consolidated, so confirm the current document.

For vapor intrusion from contamination, the guidance comes from EPA's vapor-intrusion technical guidance and the ITRC vapor-intrusion documents, plus the EPA petroleum vapor-intrusion guidance for fuel sites, run through the state environmental program. Hedge the levels, the methods, and the testing to EPA, AARST, the state radon or environmental program, and the AHJ. The points that do not bend: sub-slab depressurization vents the gas out, it is not just sealing; the fan and discharge belong above the roof and away from openings; and you test before and after against the action level.

Units and terms

Radon work mixes a radioactivity unit, a few system terms, and the building-pressure idea that makes the whole thing work, so the same concept reads differently across a test report, a spec, and an environmental document.

Radon concentration is given in picocuries per liter (pCi/L) in the United States and in becquerels per cubic meter (Bq/m3) elsewhere, where roughly 37 Bq/m3 equals 1 pCi/L. Sub-slab suction is read in inches of water column on the manometer. Keep the soil-gas problem separate in your head from the liquid-water problem in the below-grade waterproofing guide and the moisture-retarder detail in the slab-on-grade guide, because the same slab can need all three.

Radon

A radioactive gas from the natural decay of uranium in soil and rock, a leading cause of lung cancer indoors

Soil gas

The air in the pore spaces of the soil under and around a building, carrying radon or contaminant vapors

Vapor intrusion

Migration of VOC vapors from contaminated soil or groundwater up into a building through the soil-gas pathway

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

Passive vs active

Passive vents by stack effect with no fan; active adds a fan and is the reliable approach

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

pCi/L / action level

Picocuries per liter, the radon unit; 4 pCi/L is the EPA action level at which mitigation is recommended

Related tools

Calculators and readiness checks for this work

Compare your options

FAQ

People also ask

• What is the difference between dampproofing and waterproofing?
• How thick should a slab on grade be?
• What is the difference between integral color and stain?
• What is an under-slab vapor barrier?
• What is an intrusion alarm system?