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What is radon mitigation?

By Radon411 Editorial TeamUpdated How we research

Short answer

Radon mitigation is work that lowers the radon level in a building, usually a vent pipe and fan system that pulls soil gas from under the home and releases it outdoors before it can enter. A qualified contractor designs it for the foundation, and a follow-up test confirms that it worked.

Next step: a certified professional designs and installs the fix. Find a mitigation professional

EPA recommends fixing a home when a confirmed test result reaches its , and considering a fix between 2 and 4 . The most common method is a vent pipe system and fan that pulls radon from beneath the house and vents it outside, and some radon reduction systems cut levels by up to 99 percent.

How do you mitigate radon, then? A qualified contractor inspects the home and picks the method that suits its foundation: soil suction under a basement or slab, a sealed plastic sheet with suction in a crawlspace, and water treatment where radon comes in through a private well. Sealing cracks and openings helps any of these work, but sealing alone is not recommended.

What to do next: if you have a single short-term result above the action level, confirm it with a follow-up test, then get quotes from certified professionals. After the system is installed, test again, and keep testing from time to time.

What mitigation means

Radon is any work that lowers the radon level in a building. There are two broad approaches: some techniques prevent radon from entering the home, while others reduce radon after it has entered. EPA generally recommends the first kind, and the method that does it, soil suction, draws radon from below the home and vents it through a pipe to the air above the roof, where it is quickly diluted.

Radon mitigation at a glance
QuestionAnswer
What is the goal?To reduce the indoor radon level as low as reasonably achievable, below EPA's action level, and often below 2 pCi/L.
What is the main method?A vent pipe and fan that pull soil gas from under the home and release it outdoors, with cracks and openings sealed.
Who does it?A qualified, often state-licensed or certified, radon mitigation contractor.
How do you know it worked?A follow-up radon test within 30 days of installation.
What does it take afterward?A fan that runs all the time, a glance at the warning device, and a retest at least every two years.

Radon reduction systems work: some cut levels by up to 99 percent, and hundreds of thousands of people have already reduced the radon in their homes.

How do you mitigate radon? It depends on the foundation

A home's foundation type largely decides the system. Homes are grouped as basement, slab-on-grade (concrete poured at ground level) or crawlspace (a shallow unfinished space under the first floor), and many have more than one, which can call for a combination of techniques.

Basement, slab-on-grade and crawlspace foundations, each with a section drawing and the radon reduction methods EPA lists for it, such as active subslab suction and submembrane suction.
Read this figure as text

  • Basement

    • Active subslab suctionThe most common and usually the most reliable radon reduction methodOne or more suction pipes are inserted through the floor slab into the crushed rock or soil underneath.
    • Drain-tile suctionSuction on drain tiles or perforated pipe is often effective in reducing radon levels.
    • Sump-hole suctionThe sump can be capped so that it can continue to drain water and serve as the location for a radon suction pipe.
    • Block-wall suctionUsed in basement homes with hollow block foundation walls, often in combination with subslab suction.
    • Passive subslab suctionRelies on natural pressure differentials and air currents instead of a fan; generally not as effective in reducing high radon levels as active subslab suction.

  • Slab-on-grade

    Concrete poured at ground level.

    • Active subslab suctionThe most common and usually the most reliable radon reduction methodSuction pipes may also be inserted below the concrete slab from outside the home.
    • Drain-tile suctionSuction on drain tiles or perforated pipe is often effective in reducing radon levels.
    • Passive subslab suctionUsually associated with radon-resistant features installed in newly constructed homes.

  • Crawlspace

    A shallow unfinished space under the first floor.

    • Submembrane suctionWhen properly applied, the most effective way to reduce radon levels in crawlspace homesA high-density plastic sheet covers the earth floor, and a vent pipe and fan draw the radon from under the sheet and vent it to the outdoors.
    • Active crawlspace depressurizationA less-favorable option that draws air directly from the crawlspace using a fan; it generally does not work as well as submembrane suction.
    • Crawlspace ventilationIn some cases, radon levels can be lowered by ventilating the crawlspace passively, or actively, with the use of a fan.

Any type of home

  • Sealing cracks and openingsA basic part of most approaches, but EPA does not recommend the use of sealing alone to reduce radon.
  • House or room pressurizationShould only be considered after the other, more-common techniques have not sufficiently reduced radon.
  • Heat recovery ventilator (HRV)More effective in reducing radon levels when used to ventilate only the basement.
  • Natural ventilationShould normally be regarded as only a temporary radon reduction approach.

Some homes have more than one foundation design feature. In these situations, a combination of radon reduction techniques may be needed to reduce radon levels to below 4 pCi/L.

The radon reduction methods for basement, slab-on-grade and crawlspace homes, and the methods that work in any home.
  • Basement and slab homes: usually one of four kinds of soil suction: subslab, drain-tile, sump-hole or block-wall. Subslab suction is the most common and usually the most reliable. See reducing radon in a basement.
  • Crawlspace homes: a high-density plastic sheet covers the earth floor and a vent pipe and fan draw radon from under it. This submembrane suction, properly applied, is the most effective way to reduce radon in a crawlspace home.
  • Any home: sealing, house or room pressurization, heat recovery ventilation and natural ventilation can help, but they are add-ons or stopgaps, not the main fix.

Mitigating radon in well water

When radon comes in through a private well, mitigation means treating the water. The radon in water poses an inhalation risk and a small ingestion risk, and most of the risk comes from radon released into the air when water is used for showering and other household uses, so the treatment that counts is the one that covers all the water entering the home.

Treating well water for radon
TreatmentWhat it doesTypical reduction
Point-of-entry aerationTreats all the water before it reaches the home's pipes; needs annual cleaning and vents radon outdoors95 to 99 percent
Point-of-entry granular activated carbon (GAC)Treats all the water; costs less than aeration but collects radioactivity and may need special disposal; for moderate levels85 to 95 percent
Point-of-use device at a tapTreats only a small part of the water, such as drinking water; does not reduce the risk from radon released into the airNot effective for the air

Test the air first. Radon entering through the soil is usually a much larger risk than radon from water. The radon in water hub and how to get radon out of water go further.

The mitigation process, start to finish

  1. Confirm the result

    Act on one long-term test or the average of two short-term tests, not a single short-term result.

  2. Find qualified contractors

    Start with your state radon office; many states require radon professionals to be licensed, certified or registered. Get bids from more than one.

  3. Walk-through and proposal

    The contractor inspects the home, may run diagnostic tests, and gives a written proposal and contract.

  4. Installation

    Suction point, pipe, fan in unconditioned space, sealing, a warning device and a label.

  5. Follow-up test

    Test within 30 days of installation, ideally with an independent tester, to confirm the level came down.

  6. Upkeep

    Keep the fan running, check the warning device, and retest at least every two years.

Cost and upkeep

Most homes can be fixed for about the same cost as other common home repairs. The price depends on the home's size and design and the methods needed, so estimates from qualified contractors are the only reliable figure for a given house; the mitigation cost page has the published ranges.

Running costs and upkeep of a mitigation system
ItemWhat to expect
ElectricityFan systems are more effective but slightly increase the electric bill.
Heating and coolingMost systems cause some loss of conditioned air; how much depends on climate, system and construction.
The fanRuns continuously; may last five years or more, then may need repair or replacement.
The warning deviceUsually a manometer; check it on a regular basis.
RetestingAt least every two years, and after any major remodel.

Questions about radon mitigation

Is radon mitigation worth it?

Lowering radon lowers lung cancer risk, even for someone who has lived with a radon problem for a long time, and some systems cut radon by up to 99 percent for about the cost of a common home repair.

Does mitigation remove all radon?

No. Outdoor air itself carries about 0.4 pCi/L. The aim is as low as reasonably achievable: below the action level, and in most homes 2 pCi/L or below.

How long does a mitigation system last?

The pipe and seals are permanent; the fan is the part that wears, lasting five years or more before it may need repair or replacement. Retest at least every two years to be sure levels stay low.

Can I mitigate radon myself?

Some people do, but EPA recommends a qualified contractor, because without the right equipment and knowledge you could raise the radon level or create other hazards. See do-it-yourself radon mitigation.

Do air purifiers mitigate radon?

They are not a radon fix; the methods that work stop radon getting in. See do air purifiers get rid of radon.

Does a mitigation system hurt resale value?

Where radon problems have been fixed, home sales have not been blocked, and the added protection can be a selling point. See does a radon mitigation system hurt resale.

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