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Mitigation

Radon mitigation: when to fix, how it is done, and how to hire for it

By Radon411 Editorial Team

Updated October 1, 2026

Methodology

Short answer

Radon mitigation is the work of lowering the radon level in a building, almost always by installing a vent pipe and fan that pull radon from under the foundation and release it outdoors. EPA recommends it when a confirmed test result reaches 4 pCi/L, recommends considering it between 2 and 4 pCi/L, and says a qualified contractor can bring most homes down to 2 pCi/L or below.

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

Key takeaways

  • Radon mitigation, radon remediation, radon abatement and radon reduction all mean the same work: lowering the radon level in a building that tested high.
  • Confirm a high first result with a second test, then fix. The line is 4 pCi/L, and a fix is worth considering between 2 and 4 pCi/L.
  • The usual fix is a soil suction system: a sealed pipe and a fan that pull radon from under the house and vent it above the roof.
  • Hire a contractor credentialed by your state or a national proficiency program, get more than one estimate, and get the work and any guarantee in a written contract.
  • Test again within 30 days of the system starting, by an independent tester if you can, and retest at least every two years.

What it is

What radon mitigation is

Radon mitigation is the work of reducing the radon in a home or other building. "", "radon reduction" and "fixing" mean the same thing, and you will also see it called remediation or abatement. Whatever it is called, the aim of every system is the same: to reduce the indoor radon level as low as reasonably achievable.

Up to 99%
How much some radon reduction systems can reduce the radon level in a home, according to EPA
2 pCi/L or below
Where a qualified contractor can bring most homes.
Within 30 days
Test again within 30 days of the system starting, but no sooner than 24 hours after.
Every two years
Retest at least every two years once a system is in.
Read moreA paragraph, 1 min

It works. Radon reduction systems work, they are not too costly, and even very high levels can be brought down to acceptable levels. Hundreds of thousands of homeowners have already fixed radon problems in their homes. This page covers the decision and the project; the hardware for each kind of house is on radon mitigation systems.

When to fix

When to mitigate: EPA's action level and a confirmed result

EPA recommends fixing a home when the radon level is 4 or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. The result that counts is one , or the average of two , at 4 pCi/L or more. A single short-term result is a reason to test again, not yet to fix.

From a first test to a decision

  1. Follow up a high first result

    If a first short-term test is at or above 4 pCi/L, take a long-term test or a second short-term test.

  2. Move fast on a very high one

    A first result more than twice the 4 pCi/L action level calls for a second short-term test immediately.

  3. Decide on the confirmed number

    Fix the home if one long-term test, or the average of two short-term tests, is 4 pCi/L or more.
Read moreTwo paragraphs, 1 min

How quickly to follow up depends on the first number. The higher the first short-term result, the more certain you can be that a short-term follow-up is the right choice, and a first result more than twice the 4 pCi/L calls for a second short-term test immediately. Results close to 4 are the least certain: an average of 4.1 pCi/L from two short-term tests gives about a 50 percent chance that the year-round average is somewhat below 4.

Below 4, the risk is still not zero: any radon exposure carries some risk, and lowering your radon level lowers your lung cancer risk. What a particular number means is on radon levels, and the question of when mitigation is required is answered in at what level does radon require mitigation.

How it works

How radon mitigation works

Most mitigation stops radon at the foundation rather than chasing it once it is inside. The method used most is a vent pipe system and fan that pulls radon from beneath the house and vents it outside, called a soil suction radon reduction system, and it does not require major changes to the home. Sealing foundation cracks and other openings makes this kind of system more effective and cost-efficient, and similar systems can be installed in houses with crawl spaces.

A sump pump standing on a covered pit in the corner of a concrete floor, in black and white
A sump pit with its cover on. Sealed, a pit like this can serve as the suction point.
Cross-section of a house with a sub-slab depressurization system: soil gas drawn from beneath the slab into a suction point, up a vent pipe, through a fan outside the living space and out above the roofline.
A soil suction (sub-slab depressurization) system, the method used most.
Read this figure as text
Sub-slab depressurization system in a house cross-sectionGround levelLiving spaceBasement12345
  1. Soil gas drawn from beneath the slab
  2. Suction point through the slab
  3. Vent pipe
  4. Fan, outside the living space
  5. Discharge above the roofline
Show the whole figure
Read moreA paragraph, 1 min

These systems keep radon from entering from below the concrete floor and from outside the foundation, and contractors may use other methods that suit a particular house. The right system depends on the design of the home and other factors. Each design, from sealed sumps to crawl space membranes, is explained on radon mitigation systems.

The process

The radon mitigation process, step by step

A mitigation project runs in ten steps. In order:

Steps in an installation

  1. A test shows a radon problem

    A confirmed result at or above the action level, or one you have decided to lower.

  2. Request bids

    Contact licensed or certified mitigation professionals and ask each for a proposal.

  3. Walk-through

    The professional walks through the home to lay out how the system will be built.

  4. Ask the key questions and get a proposal

    Use the contractor checklist below.

  5. Choose a professional

    Compare what each proposal includes, not only the price.

  6. Diagnostics

    The professional may test under the slab to choose the right fan size and placement.

  7. Sealing

    Cracks and openings in the basement are sealed.

  8. Installation

    The pipe, fan, exhaust, warning device and label go in.

  9. Explanation

    The installer shows you how the system operates and leaves written instructions.

  10. Retest

    A new test confirms the system has reduced the radon level.

Hiring

Hiring a radon mitigation contractor

EPA recommends a certified or qualified radon mitigation contractor trained to fix radon problems. Start with your state radon office: many states require radon professionals to be licensed, certified or registered and to install systems that meet state rules, and most can provide a list of providers working in the state. States that receive federal indoor radon grants must give the public a list of only those providers credentialed either by the state or by one of the two national programs, the National Radon Proficiency Program () and the National Radon Safety Board ().

A checklist for comparing radon mitigation contractors

  • References, photographs and before-and-after test results from past jobs

    Shows the results of past radon reduction work

  • What the work involves, how long it will take and exactly how the system will work

    You should understand the design before you sign

  • Is there a fee for diagnostic tests?

    Many give free estimates but charge for diagnostics, which are sometimes necessary

  • Did they inspect the house before quoting?

    A quote made without seeing the house is a guess

  • Did they review your test results and whether the test was done properly?

    The contractor should review the measurements before any work

  • Proof of state certification or a proficiency credential

    Required in many states

  • Proof of liability insurance, bonding and local licenses

    Protects you if someone is hurt or something is damaged

  • A warning device, and testing after installation

    Both should be in the proposal

  • A guarantee to reach 4 pCi/L or below, and for how long

    Sets what happens if the first retest is high
Show all 9 cards
Read moreA paragraph and a note, 1 min

Choose a contractor the way you would for any other home repair: get more than one estimate, ask for references and call some of them. Your county or state consumer protection office may also have information. Certified installers in each state are listed in the mitigation professionals directory.

The contract

What a radon mitigation estimate and contract should include

Ask the contractor for a contract before any work starts, read it before you sign, and check that it matches the original proposal. It should describe exactly what work will be done before and during the installation, what the system consists of and how it will operate. Many contractors guarantee to adjust or modify the system until it reaches a negotiated radon level, such as 2 pCi/L or less, so read the conditions of that guarantee closely.

What a radon mitigation contract should contain
ItemWhat to look for
PriceThe total cost, including all taxes and permit fees; any deposit; when payment is due in full
ScheduleThe time needed to complete the work
Permits and codesAn agreement to obtain necessary permits and follow required building codes
InsuranceA statement that the contractor carries liability insurance and is bonded and insured
Damage and cleanupA guarantee that the contractor is responsible for damage during the job and cleanup after it
Radon guaranteeDetails of any guarantee to reduce radon below a negotiated level
Hardware warrantiesDetails of warranties or optional features for the system's components
TransferWhether warranties or guarantees transfer if you sell the home
Your partWhat the contractor expects you to do before work begins, such as clearing the work area
Show all 9 rows
Read moreA paragraph, 1 min

Optional additions cost more up front but may be worth it, such as an extended warranty, a service plan or improved appearance. When comparing quotes, a less expensive system may cost more to operate and maintain or look worse, a more expensive one may be best for your home, and the quality of the materials affects how long a system lasts.

By foundation

Radon mitigation by foundation: basement, slab and crawl space

The house's foundation decides the method. Homes are grouped as basement, slab-on-grade (concrete poured at ground level) or crawl space, and many combine two. Basements and slabs are usually fixed with one of four kinds of soil suction; crawl spaces with a plastic sheet over the earth floor and suction beneath it. Where a home has a basement under part of it and a slab or crawl space under the rest, a combination of techniques may be needed.

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.
The methods for each foundation type, and the ones that work in any home.
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.

Show the whole figure

Radon mitigation in a finished basement

Two paragraphs, 1 min

A finished basement can be mitigated, and timing helps. If you plan to finish or renovate an unfinished area, test before the project and after, because it is generally less expensive to install a radon-reduction system before or during renovations than afterwards. If test results show a problem, radon-resistant techniques can be inexpensively included as part of the renovation.

For a basement-specific walk-through, see how to reduce radon gas in a basement; for slab homes, can a house have radon without a basement.

Results

How much radon mitigation lowers radon

Radon levels in most homes can be reduced to 2 pCi/L or below with today's technology. Typical reductions run 50 to 99 percent for each of the active soil suction methods and for basement pressurization, 30 to 70 percent for a passive sub-slab system, and 0 to 50 percent for crawl space natural ventilation. Every system should get the level below 4 pCi/L, and a quality system may bring year-round levels below 2.

50 to 99 percent
Typical reduction for each active soil suction method and for basement pressurization.
30 to 70 percent
Typical reduction for a passive sub-slab system.
0 to 50 percent
Typical reduction for crawl space natural ventilation.
Read moreA figure and a paragraph, 1 min

Typical radon reduction, EPA

Basement and slab-on-grade homes

  • Subslab suction (subslab depressurization)50 to 99 percentWorks best if air can move easily in material under slab.
  • Passive subslab suction30 to 70 percentMay be more effective in cold climates; not as effective as active subslab suction.
  • Drain tile suction50 to 99 percentCan work with either partial or complete drain tile loops.
  • Block-wall suction50 to 99 percentOnly in homes with hollow block-walls; requires sealing of major openings.
  • Sump-hole suction50 to 99 percentWorks best if air moves easily to sump from under the slab.

Crawlspace homes

  • Submembrane depressurization in a crawlspace50 to 99 percentLess heat loss than natural ventilation in cold winter climates.
  • Natural ventilation in a crawlspace0 to 50 percentCosts variable.

Any type of home

  • House (basement) pressurization50 to 99 percentWorks best with tight basement isolated from outdoors and upper floors.
  • Sealing of radon entry routesSee commentsNormally only used with other techniques; proper materials and installation required.
  • Natural ventilationVariable/TemporarySignificant heated or cooled air loss; operating costs depend on utility rates and amount of ventilation.
  • Heat recovery ventilation (HRV)VariableLimited use; effectiveness limited by radon concentration or the amount of ventilation air available for dilution by the HRV.
Typical radon reduction for each technique.

Congress set a long-term goal that indoor radon be no higher than outdoor air, where about 0.4 pCi/L is normally found; that is not yet technologically achievable in every case. Whether mitigation reliably works is answered in does radon mitigation work, and whether radon can be taken out entirely in can radon be removed.

DIY

DIY radon mitigation

EPA recommends a qualified contractor because lowering high radon levels takes specific technical knowledge and special skills; without the right equipment or knowledge you could raise your radon level or create other hazards and costs. Put plainly, contractors who do not specialize in radon reduction could make the problem worse. If you decide to do it yourself, start with your state radon office, for guidance and for training courses.

Read moreA paragraph, 1 min

Whoever does the work, the same test applies afterwards. The trade-offs are set out in do it yourself radon mitigation, and the steps of a basement installation in how to install a radon mitigation system in a basement.

In the meantime

Before the system goes in: temporary steps

There is no quick substitute for a system, but some things help in the meantime: increase air flow by opening windows and using fans and vents to circulate air, and seal cracks in floors and walls with plaster, caulk or other materials made for the purpose, then test again after any change. Natural ventilation should not be considered radon mitigation, because it is only temporary.

What temporary steps do

  • Opening windows, doors and vents on lower floors

    Can reduce radon, but once closed, levels most often return to previous values within about 12 hours

  • Natural ventilation in general

    Only a temporary approach, with lost conditioned air, higher energy costs and security concerns

  • Sealing cracks

    Part of most approaches, but sealing alone is not recommended, because it has not been shown to lower radon significantly or consistently

  • Any change

    Test radon levels again afterwards
Show all 4 cards
Read moreA paragraph, 1 min

See also does opening windows reduce radon and would an exhaust fan in a basement reduce radon.

Cost

Radon mitigation cost

Most homes can be fixed for about the same cost as other common home repairs, and the cost depends on how the home was built and the extent of the radon problem. In choosing a method, you and the contractor weigh how high the initial radon level is, the cost of installation and of running the system, the size of the home and its foundation type. The cost is much less if a passive system was installed during construction. Two published estimates give a sense of scale: in general $1,500 to $3,000 for a system in Minnesota, by the state health department's estimate, and around $200 to $350 to replace a fan, parts and labor included, by EPA's.

$1,500 to $3,000
In general, for a system in Minnesota, by the state health department's estimate.
Around $200 to $350
To replace a radon fan, parts and labor included, by EPA's estimate.
About the same
As other common home repairs, for most homes.
Read moreA paragraph, 1 min

Financial assistance may be available in some states, depending on household income, location and funding. Every cost figure, and what makes one quote higher than another, is on radon mitigation cost.

Afterwards

After mitigation: the retest, upkeep and retesting

A system is only finished when a test says so. Test within 30 days of installation, but no sooner than 24 hours after the system is running, with a two- to seven-day measurement under , ideally by an independent, qualified tester. Ask the contractor to explain how the system operates and to leave written operating and maintenance instructions and copies of any warranties.

Timeline after a radon mitigation system is installed: the fan runs continuously, test no sooner than 24 hours and within 30 days, then retest at least every two years.
Testing after installation, then at least every two years and after a remodel.
Read this figure as text

  1. Day of installation

    The system goes in

    Keep the fan running at all times: it must run continuously for the system to work correctly.

  2. No sooner than 24 hours

    Earliest post-mitigation test

    Test no sooner than 24 hours after your system is in operation with the fan on, if it has one.

  3. Within 30 days

    Post-mitigation test done

    A two- to seven-day measurement is recommended, and EPA recommends an independent follow-up radon measurement as well as any test the contractor runs.

  4. At least every two years

    Retest

    Retest your home at least every two years to be sure radon levels remain low.

Test conditions: Windows and doors must be closed 12 hours before and during the test, except for normal entry and exit. Not drawn to scale.

After a remodel. After you remodel, retest in the lowest lived-in area to make sure the construction did not reduce the effectiveness of the radon reduction system.

Show the whole figure
Read moreA paragraph, 1 min

After that, upkeep is light. Look at the warning device, usually a manometer, regularly; the fan should never be turned off; and retest at least every two years. Fans may last five years or more and may then need repair or replacement. Living with a system is covered in the radon system guide, and how soon to retest in how long after radon mitigation can you retest.

Test kits and monitors for the retest42

All products

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Home sale

Radon mitigation when buying or selling a home

It is better to correct a radon problem before a home goes on the market, because then there is more time to deal with it. If high levels turn up during a sale, the buyer and seller should discuss the timing and costs of radon reduction, and the purchase contract can say when mitigation will be done and who will pay for it.

Mitigation in a home sale: what each side should do

  • Seller

    Test before listing and fix if necessary; save the results and the records of any fix, which could be a selling point

  • Seller with a system

    Tell buyers about it and give them information on its operation and maintenance

  • Buyer

    Ask for the seller's test results and any information about an existing system

  • Both

    If levels are high during the sale, discuss timing and costs; write into the contract when mitigation happens and who pays
Show all 4 cards
Read moreA paragraph, 1 min

A common worry has a reassuring answer: where radon problems have been fixed, home sales have not been blocked. More is in the buying a house with radon and selling a house with radon guides.

Renovations

Renovations, additions and a system already in place

Major renovations can change the radon level in any home, so test again when the work is done. If you plan big structural changes after a system is in, such as turning an unfinished basement into living space, ask your radon contractor whether the changes could void any warranties; if you plan a new foundation for an addition, ask what is needed to keep levels low throughout the home. After remodeling, retest in the lowest lived-in area.

Questions

Radon mitigation questions

What happens if a house tests positive for radon?

A radon test gives a number, not a yes or no. If a first short-term test is at or above 4 pCi/L, confirm it with a long-term test or a second short-term test, then fix the house if the long-term result or the average of the two short-term tests is 4 pCi/L or more.

Is radon remediation the same as radon mitigation?

Yes. Remediation, abatement, reduction and mitigation all describe lowering a building's radon level; "radon reduction" and "mitigation" are the most common terms.

Does radon mitigation work?

Yes. Radon reduction systems work, some reduce levels by up to 99 percent, and most homes can be brought to 2 pCi/L or below. A test after installation confirms it for your house.

Can I do radon mitigation myself?

Some states allow it; contact your state radon office first for guidance and training. EPA recommends a qualified contractor because a poorly built system can raise radon levels or create other hazards.

Do I need a licensed or certified radon mitigator?

It depends on the state. Many require radon professionals to be licensed, certified or registered. Where a state does not, ask for a credential from a proficiency program such as NRPP or NRSB.

What should a radon mitigation contract include?

The total cost with taxes and permits, the schedule, permits and code compliance, insurance and bonding, responsibility for damage and cleanup, any radon-level guarantee, hardware warranties, whether they transfer on sale, and what you need to do before work starts.

Can the company that tested my house install the system?

It can, but it is a potential conflict of interest, and some states require a signed waiver. Either way, have an independent test done after the system is installed.

How soon after mitigation can I retest?

No sooner than 24 hours after the system starts running, and within 30 days of installation, using a two- to seven-day test with windows and doors closed.

Can you mitigate radon in a finished basement?

Yes. It is generally cheaper to install a system before or during a renovation than after, so test before finishing a basement if you can.

What can I do while I wait for a radon system?

More ventilation and sealing cracks help as interim steps; test again afterwards. Opened windows only help while they are open: radon most often returns to previous levels within about 12 hours of closing them.

Who pays for radon mitigation in a home sale?

That is for the buyer and seller to settle: discuss timing and costs, and write into the contract when mitigation will happen and who will pay.

Is there help paying for radon mitigation?

Some states offer it, depending on household income, location and funding. Ask your state radon office.

Does radon mitigation take care of radon in well water?

No. Soil suction treats soil gas. If you have a private well, test the water separately and see radon in water for the treatment systems.