Last updated 2026-08-19
TL;DR
Radon mitigation lowers indoor radon, usually with a sealed pipe and a continuous fan that pulls soil gas from under a slab or crawl space and vents it above the roof. Start by confirming a real high reading. EPA treats 4 pCi/L as the action level. Then check whether your state licenses mitigators before you drill. Get the named credential and the current standard. Bid only what you can document.
What is radon mitigation?
Radon mitigation is the set of building changes that lower the radon concentration inside a house or other occupied space. The usual residential system is active soil depressurization. A fan pulls soil gas from under a slab or from a sealed crawl space and vents it outdoors above the roof, so less radon enters the living space.
That is the job. You change pressure and air paths. You do not filter radon with a gadget on the furnace.
EPA's Citizen's Guide states, "Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils." [1] It moves with soil gas. A house that sits at lower pressure than the soil pulls that gas in through cracks, sumps, and utility penetrations. Once inside, radon collects. The reason anyone pays for mitigation is lung cancer risk. EPA estimates 21,000 U.S. lung cancer deaths each year are related to radon. [3]
Mitigation is not the test. A measurement tells you the number. Mitigation changes the building so the next number is lower. Keep those functions separate on invoices and in your files, even when one firm holds both credentials. Several states want that split written down. See how testers and mitigators get split on paper in our comparison on dual credentials.
You will see a short list of system types on real jobs. Sub-slab depressurization on poured slabs and most basements. Sub-membrane depressurization on dirt crawl spaces, with a sealed polyethylene sheet. Drain-tile or sump suction where the plumbing already gives you a collection path. Block-wall suction on some hollow masonry foundations. That last one is easy to do badly.
I would not sell air cleaners, ionizers, or radon paint as mitigation. Opening a window is not a system. Ventilation can nudge a number. It will not carry a real estate file.
WHO puts the health point in one line: "Radon is the most important cause of lung cancer after smoking." [6] NCI's fact sheet walks the same risk path and points back to the National Academy BEIR VI review. [5][12]
How do you start radon mitigation?
You start radon mitigation by confirming a real indoor reading, then by confirming you are allowed to do the work in that state, then by designing a system that matches the foundation in front of you. Do not buy a fan first. The number and the paper come first.
Homeowners start with a test. Short-term devices run a few days. Long-term tests run 90 days or more and track the year better. EPA recommends fixing a home if one long-term test or the average of two short-term tests shows 4 pCi/L or higher. [1] You can decide to fix between 2 and 4. Plenty of people do.
If you are entering the trade, the start sequence is not a shopping cart.
Read the current ANSI/AARST soil gas mitigation standard for the building type you will touch. An existing house is not a school. It is not new construction either. [10]
Call or write your state radon office and ask whether mitigation is licensed, certified, registered, or left alone. EPA keeps a public list of state contacts and radon zone maps for that first call. [4] Zone maps are not work orders. They are a starting hint.
If the state names NRPP or NRSB, complete the training and exam that body actually requires this year. Confirm the live steps on the credentialing page. Do not trust a forum recap. [9]
Carry the insurance and the local permits the building department names. I am not your lawyer. Some towns want a mechanical permit for the penetration and the wiring. Some want nothing.
Shadow installs if you can. A few states require supervised work. Many do not. Walk every house you bid. Look at the foundation, the sump, the crawl height, the discharge path, and the electrical panel before you quote.
People skip the state call and get a notice of violation. I would not.
A paper kit does not replace the board. If you want the forms and checklists we publish in one packet, RadonPath sells a $149 one-time NRPP Mitigation Kit (see /start). The board still wins if the packet and the statute disagree.
What radon number actually triggers a job?
EPA's action level is 4 pCi/L. That is the number most U.S. real estate contracts and most state programs still use when they say a house needs mitigation. [1]
The EPA Citizen's Guide lists a national average indoor radon level of 1.3 pCi/L and an outdoor average of 0.4 pCi/L. [1] WHO's published reference level is 100 Bq/m³, about 2.7 pCi/L. [6] EPA also says consider fixing between 2 and 4 pCi/L. There is no known safe concentration. Risk rises with the number and with time in the room. [3][5]
Convert when you have to. 1 pCi/L equals 37 Bq/m³. Memorize that. Lab reports mix units.
| Number | What it is | Source |
|---|---|---|
| 0.4 pCi/L | U.S. outdoor average | EPA Citizen's Guide (2016) |
| 1.3 pCi/L | U.S. indoor average | EPA Citizen's Guide (2016) |
| about 2.7 pCi/L | 100 Bq/m³ WHO reference level | WHO radon fact sheet |
| 4 pCi/L | EPA action level | EPA Citizen's Guide (2016) |
I treat 4.0 as the contract trigger and anything persistent above 2 as a conversation. Some clients want as low as the house will go. Say that in writing so you are not arguing later about 3.6 versus 3.1.
County zone maps from EPA put counties in Zone 1, 2, or 3 by predicted average potential. [4] A Zone 3 county still has high houses. A Zone 1 county still has low ones. Test the building. Do not mitigate a map.
If you want a side-by-side of how different writeups treat the same trigger numbers, read the comparison on action levels.
What does a mitigation system actually do in the house?
A typical residential system creates a small vacuum under the slab or under a crawl-space membrane, then dumps that soil gas above the roof. The fan runs all the time. A U-tube or magnehelic gauge on the pipe shows the homeowner the system still has suction.
You core a hole. You make a suction pit by removing soil or breaking a bit of slab. You run PVC. You seal the slab penetration. You seal big openings (open sumps, large cracks, unused floor drains) enough that the fan is pulling on soil, not on basement air. You wire the fan to a dedicated or clearly identified circuit. You label the system. You leave the owner a packet.
The 2016 EPA Consumer's Guide to Radon Reduction still describes active soil depressurization as the method used most often in existing houses. [2] That matches what you will see on the street.
Discharge location matters. You want the exhaust high, away from openings that would pull the gas right back in. The current AARST standard is stricter than the folklore you will hear on job sites. Follow the standard, not the folklore. [10]
Fans fail. Pipes crack. Homeowners turn breakers off. Plan for that in the owner packet. A dead fan is an unmitigated house.
Crawl-space work is a different day than a clean basement slab. Membrane quality and sealing eat the clock. Price it that way. For a system-type cost walk-through, see the comparison across mitigation layouts.
Do you need a license to mitigate radon?
Sometimes. Many states license or certify radon mitigators. Some do not. You cannot assume a national rule. There is not one.
Florida law addresses radon certification in section 404.056, Florida Statutes, including public information and certification duties for the radon program. [7] Illinois regulates the trade under the Radon Industry Licensing Act, 420 ILCS 44. [8] Pennsylvania has run a radon certification program for decades through its radiation protection office. [13] Other states require nothing at the state level and leave you with local permits and ordinary contractor rules.
NRPP and NRSB credentials are national voluntary certifications. A lot of states point to one of them, or accept them, or ignore them. Confirm the current acceptance language with the state office, not with a trainer's slide. [4][9]
I would not bid a house in a licensed state until my name (or my firm's name) matches what that statute requires. Working on a buddy's credential is how people lose both credentials.
Fees, application windows, and renewal cycles change. Confirm every dollar and every form with the board that can fine you. Nobody honest publishes a single national fee table that stays true.
If you want a credential-by-credential comparison, we keep that in the comparisons hub. Use it as a map, then read the statute.
What paper should you have before you bid?
Before you bid, you want a current mitigation credential the state will recognize, a written test report that justifies the work, proof of insurance, and a clear sense of whether the town wants a permit. That is the minimum paper stack I would take to a first job.
Add a contract that states the pre-mitigation number, the method, the discharge plan, who does the post-test, and what happens if the first design does not get under the agreed target. Add photos. Add a simple floor sketch. Future you will need them when a realtor calls in six months.
If you also test, keep the measurement file clean. Chain of custody, device serials, closed-house conditions. Sloppy test paper makes a perfect install look like a fight.
Local electrical rules sneak up on people. An exterior fan still needs a legal disconnect and weatherproof connections. Ask the inspector before you cut.
I do not write legal advice. An article is not a board opinion. Your statute and your attorney beat this page if they disagree.
On the van I want the standard, the contract, the pre-test, and a way to photograph the manometer at handover. That is enough to start. Fancy software can wait until the paper habit exists.
How much does radon mitigation cost the homeowner?
The 2016 EPA Consumer's Guide to Radon Reduction put typical system cost at $800 to $2,500. [2] That is a real federal range. It is also a 2016 range.
Current bids in many markets run higher. Labor, fans, and insurance moved. Nobody has a single official 2026 national price file. If a website tells you the average U.S. system is exactly one number this year, treat it as marketing. Get three local quotes or, if you are the contractor, price the house you walked.
Hard crawl spaces, thick commercial slabs, and houses that need two fans cost more. Simple basement slabs with a clean exterior chase cost less. I would rather lose a bid than invent a one-day price for a two-day membrane job.
Operating cost is fan electricity, 24 hours a day. Think in the same neighborhood as a continuously running bath fan, then check the watt rating on the unit you actually install. Do not quote a utility savings you cannot show.
Ask what the quote includes: sealing, electrical, permit, post-test, and a return visit if the first suction point is weak. Cheap bids hide those lines. For more system-to-system money talk, use the layout comparison and then reprice locally.
What training and exams do new mitigators take?
New mitigators usually take a state-accepted or NRPP/NRSB-accepted training course, sit an exam, and file an application with whoever has jurisdiction. That is the ordinary path. The exact hours, fees, and whether you need documented field time are not national constants. [9]
Confirm the current course list and the current application steps on the NRPP initial certification page, or on NRSB's equivalent, and on your state radon office site. [9][4] Trainers sell seats. Boards issue the card. Know which one you are talking to.
I would take a course that teaches the current ANSI/AARST residential standard, not a war-story seminar. You need pressure-field thinking, pipe judgment, crawl-space membranes, electrical basics, and the documentation the standard expects. [10]
Exam prep is dull. Do it anyway. The questions track the standard and the health facts, not your favorite fan brand.
If your state has no license, you can still be sued, and realtors can still refuse your work. A national credential is not magic. It is often the minimum a listing agent will recognize.
Compare course and credential routes in the credential comparison piece. Then file what your state named, not what a comment thread prefers.
What standard do you follow on a residential install?
On existing homes, the document you should work to is the current ANSI/AARST soil gas mitigation standard for that building type (SGM-SF for many single-family houses). EPA points practitioners and the public to consensus radon standards of practice rather than treating old EPA construction manuals as live code. [10]
Read the edition that is in force. Standards get revised. Working from a photocopied 1990s EPA mitigation handbook is how you miss discharge clearances, labeling rules, and fan-failure notification language.
Schools, multifamily buildings, and new construction have their own AARST standards. Do not mix them. A multifamily riser plan is not a bungalow sump job.
I keep a marked paper copy in the van and a paid digital copy in the office. The van copy gets dirty. That is fine.
If two editions disagree, the one your state or your contract named wins. For a walk through edition differences, see the standards comparison.
Field techs skip the labeling and owner-packet clauses because those clauses feel bureaucratic. They are how the next buyer knows what they inherited. Put the label where someone can read it without a ladder over a wood stove.
How do you prove the system worked?
You prove a system worked with a post-mitigation radon test run after the fan has been operating, plus a quick check that the manometer shows suction. The test is the result. The gauge is the is-it-on check.
EPA's consumer guidance tells people to retest after a system is installed. [2] The consensus mitigation standard sets timing details (a short wait after fan-on, then a test inside a defined window). Read the current edition for the exact hours and days. I will not pretend one article can outlive a standard revision. [10]
Closed-house conditions still matter. A wide-open spring weekend can flatter a mediocre install. Follow the measurement protocol you claimed on the report.
I like an independent tester on real estate deals. If you test your own work, say so on the report. Some states restrict who may do that post-test. Confirm it. [4][7][8]
Retest every two years, and after big renovations or a fan replacement. That is the usual owner advice from EPA materials. [1][2] Put it in the packet so you are not the villain later.
A house that stays at 3.8 pCi/L after one pipe may need a second suction point. Do not fake the number. Redesign.
What should you skip in year one?
Skip the franchise pitch until you have paid yourself for a year of real installs. Skip radon-neutralizing paints and furnace add-ons. Skip the giant diagnostic toy kit before you can use a basic micromanometer in your sleep.
Do not buy 40 fans because a supplier ran a bulk special. Fans sit. Models change.
Do not work out of state on a reciprocal story you cannot print from the other board's site.
Do buy the current standard, a decent core rig you can control, a calibrated micromanometer, labels, and a simple photo workflow. Buy insurance you actually understand. Buy one good hole-saw set and stop snapping cheap bits in rebar.
Year one is a craft year. The money is in clean one-day slabs and honest crawl quotes, not in a wrap on the van.
Another leak is underbidding to collect praise online. You will win the cheap house and inherit the callback. Charge enough for a second suction point if the first field of pressure is weak.
A comparison of first-year operating choices is worth a read before you sign a lease on a second storage unit.
How long does a typical job take from test to fan-on?
A short-term test takes about two to seven days, plus shipping or download time. A long-term test takes 90 days or more. [1] The mitigation install on a straightforward basement often fits in one workday. Crawl membranes and odd discharge paths do not.
After the fan is on, you wait at least a day before a short-term post-test in most protocols, then you get a number. [2][10] Real estate calendars will try to compress that. The protocol is not optional because a closing is Tuesday.
I do not give approval timelines for licenses. Boards change queues. Ask the board.
Weather, frozen ground, and HOA aesthetic rules add days. Write that into the contract so you are not promising a Friday fan-on you cannot hit.
Commercial and large multifamily calendars are a different sport. Do not use a bungalow day-count on a 40-unit slab. Walk it. Write a phasing plan. Then add slack.
Where do first-year mitigators actually get work?
First jobs usually come from failed real estate tests, from testers who do not mitigate, and from homeowners who already bought a kit and hated the number. That is enough pipeline if you are competent and fast on the phone.
Do not mail every address in an EPA Zone 1 county. [4] That is a waste of stamps and a good way to look like a scammer.
Be decent to testers. A clean install and a readable owner packet get you the next referral. A hidden pipe and a dead manometer do not.
Price enough to come back when the first suction point is not enough. Warranty language should match what you can actually do (fan replacement windows, not a lifetime promise on soil).
Keep a simple job log: address, foundation, pre-number, method, post-number, fan model. Future you will need it for the board, for a dispute, or for your own learning. CDC's radon explainer is useful when a client wants a health page that is not your quote sheet. [11]
RadonPath publishes reference material for people entering this trade. We are not a law firm and not a mitigation company. Confirm fees, forms, and whether you may even offer the work with the board that has jurisdiction. Then go walk the house.
Frequently asked questions
What is radon mitigation?
Radon mitigation is work that lowers indoor radon, usually by pulling soil gas from under a slab or crawl-space membrane and venting it above the roof with a continuous fan. It is a building pressure change, not an air filter. Testing measures the gas. Mitigation changes the house so the next test is lower. EPA treats 4 pCi/L as the U.S. action level for fixing a home.
How do you start radon mitigation?
Confirm a real test result first. Then check whether your state licenses or certifies mitigators before you drill. Read the current ANSI/AARST standard for that building type. Complete the credential your state actually names (often NRPP or NRSB). Walk the foundation, then bid. Homeowners start with a test and a written quote from someone who can show their paper.
Is radon mitigation the same as radon testing?
No. Testing measures radon in air over a set period. Mitigation installs a system that changes how soil gas enters the building. Keep the files separate. Some states restrict who may test a house they just mitigated. Confirm that with the state radon office before you offer both on the same job.
Can a homeowner install their own radon system?
In some unlicensed states, a homeowner can work on their own house. It can still violate local permit rules, and it can wreck a real estate deal if the install does not meet the current standard. In licensed states, the statute may forbid unlicensed mitigation even for the owner. Ask the state office and the building department before you rent a core drill.
What is active soil depressurization?
Active soil depressurization (ASD) is the common residential method. A fan draws a slight vacuum under the slab or under a sealed crawl-space sheet and dumps that soil gas outdoors, high on the building. The goal is to reverse the pressure that normally pulls radon inside. EPA's consumer guide still treats this family of systems as the usual fix for existing homes.
How low should radon be after mitigation?
EPA's action level is 4 pCi/L, and EPA also invites people to consider fixing between 2 and 4. After a system is on, the honest target is as low as the house will reasonably go, with 4 as the line most contracts still use. If the first design lands at 3.8, add suction or fix leaks. Do not dress up the report.
Does a radon fan run all day?
Yes. A mitigation fan is meant to run without stopping. When it stops, the house starts behaving like an unmitigated house again. The U-tube or magnetic gauge on the pipe is there so anyone can see suction at a glance. Teach the owner to look at it. A silent fan is a service call, not a finished system.
Do you need a permit for radon mitigation?
Sometimes. State radon credentials and local building permits are different papers. Some towns want a mechanical or electrical permit for the penetration and the fan circuit. Some want nothing. Ask the building department that will inspect the house. Do not assume a state card replaces a local permit, or the reverse.
What is NRPP certification?
NRPP is a national voluntary certification program for radon professionals, including mitigation. Many states point to it or accept it. It is not a federal license. Initial steps live on NRPP's own certification pages and include training and an exam. Confirm the live requirements there. Your state may add its own application on top.
How often should you retest after mitigation?
Retest after the system is installed and stable, then about every two years, and after major renovations or a fan change. That is the usual advice in EPA consumer materials. Real estate deals may demand a fresh short-term test on their own clock. Follow the measurement protocol you put on the report.
What does pCi/L mean?
Picocuries per liter. It is the U.S. unit for radon in air. One pCi/L equals 37 becquerels per cubic meter (Bq/m³), the unit WHO and many labs use. EPA's action level is 4 pCi/L. WHO's reference level is 100 Bq/m³, about 2.7 pCi/L. Read the unit on every lab report before you quote a client.
Is crawl space mitigation different from basement work?
Yes. Crawl work is usually sub-membrane depressurization. You seal a polyethylene sheet to walls and piers, then pull from under that sheet. Sealing time dominates the day. A clean basement slab is often a core, a pit, a pipe, and an exterior fan. Price and schedule them as different jobs. They are.
Which states require a radon mitigation license?
There is no single list that stays true without the state office. Florida, Illinois, and Pennsylvania are examples of states with statutory or program certification. Other states require nothing at the state level. EPA publishes state radon contacts. Use that list, then read the statute the contact names. Confirm before you bid.
Can opening windows replace a mitigation system?
No. Open windows can dilute indoor radon for a while and they wreck a closed-house test. They are not a labeled, measurable, always-on control. A real system keeps suction on the soil when the house is shut in January. Do not sell ventilation theater as mitigation.
Sources
- U.S. EPA, A Citizen's Guide to Radon (2016): Defines radon as a radioactive gas from uranium in soil; recommends fixing at 4 pCi/L; lists 1.3 pCi/L indoor and 0.4 pCi/L outdoor averages
- U.S. EPA, Consumer's Guide to Radon Reduction (2016): Active soil depressurization is the usual existing-home method; typical system cost given as $800 to $2,500; retest after installation
- U.S. EPA, Health Risk of Radon: EPA estimates about 21,000 U.S. lung cancer deaths each year related to radon
- National Cancer Institute, Radon and Cancer fact sheet: Radon exposure raises lung cancer risk; NCI points to the BEIR VI risk assessment
- World Health Organization, Radon and health fact sheet: WHO states radon is the most important cause of lung cancer after smoking and publishes a 100 Bq/m³ reference level
- Florida Statutes section 404.056 (2023): Florida statute 404.056 addresses radon protection, public information, and certification duties
- U.S. EPA, Radon Standards of Practice: EPA directs practitioners to consensus ANSI/AARST radon standards of practice
- CDC, Protect Yourself and Your Family from Radon: CDC publishes a public explainer on indoor radon risk and testing
- National Academies, Health Effects of Exposure to Radon (BEIR VI): BEIR VI is the National Academy review of radon's lung cancer risk
- Pennsylvania DEP, Radon Certification: Pennsylvania runs a state radon certification program for testers and mitigators