Last updated 2026-08-19
TL;DR
Radon mitigation is the work of lowering indoor radon, usually with a fan and pipe that pull soil gas from under the slab. You start by checking your state board, earning a credential they accept, then pulling local permits. EPA tells occupants to fix a home at 4 pCi/L or higher. There is no single national license.
What is radon mitigation?
Radon mitigation is the building work that lowers indoor radon gas so occupants breathe less of it. In existing houses that almost always means an active soil depressurization system: sealed suction under the slab or crawl membrane, a PVC stack, and a continuous fan that vents above the roof.
That is the job. You are moving soil gas out before it enters living space. You are not scrubbing radon out of room air with a filter. Charcoal boxes and ionizers are not mitigation. EPA's consumer guide treats soil depressurization as the usual, reliable approach [3].
Radon itself is a colorless radioactive gas from the decay of uranium in soil and rock. It rides with soil gas. It can also ride with some private well water. Indoor levels jump around from house to house on the same block. EPA puts the average U.S. indoor level at about 1.3 pCi/L and outdoor air at about 0.4 pCi/L [2]. Nearly 1 in 15 U.S. homes is estimated to sit at or above 4 pCi/L [2].
Why anyone pays you is not a mystery. EPA estimates radon causes about 21,000 lung cancer deaths each year in the United States [1]. Risk climbs with concentration and years in the building, and it is much higher for people who smoke. The National Cancer Institute states that radon is the second leading cause of lung cancer in the U.S., after smoking [5]. WHO's fact sheet puts radon's share of lung cancers in a range of 3 to 14 percent, depending on the country and the smoking mix [4].
Mitigation is a building trade with a radiation story attached. The physics is simple. The paper is not. If you came here for one federal card that covers every county, stop looking. There is no national radon contractor license.
How do you start radon mitigation?
You start with paper, not a truck wrap. Read your state's radon statute if it has one, then the contractor board, then the local building department. Take a board-accepted mitigation course and exam, hang the insurance the AHJ will ask for, and only then bid a house. Skip that order and you will redo work.
I would print the statute and the exam candidate handbook the first week. Then I would call the state radon contact EPA lists and ask what credential they will accept on a job tomorrow [6]. Write down the name of the person who answered.
The national piece is usually NRPP or NRSB. EPA tells the public to hire a professional who is state certified or listed with one of those two programs [6]. That is not a license to contract. Many states still want a separate contractor registration, plus electrical rules for the fan circuit. Extension pages written for homeowners, such as the University of Minnesota brief on testing and mitigation, use the same hire-a-listed-pro language you will hear on sales calls [15].
Pick a first state and stay there for a year. The paper path in Alabama is not the paper path in Colorado. If you need a state walkthrough, start with something concrete like how to start radon mitigation in Alabama or how to start radon mitigation in Colorado. A mountain rule does not match a Gulf Coast rule.
Your first paid job should be a simple slab ranch with a sump you can seal, not a split-level with a block wall and a wet crawl. One clean soil system and a passing post-test will teach you more than a weekend of videos.
What radon level actually triggers mitigation work?
EPA tells people to fix a home if the confirmed radon level is 4 pCi/L or higher [2]. Between 2 and 4 pCi/L, EPA says consider fixing it. That 4 pCi/L figure is guidance, not a federal law that forces every owner to hire you.
Read the Citizen's Guide line itself: "Fix your home if your radon level is confirmed to be 4 picocuries per liter (pCi/L) or higher" [2]. Confirmed matters. One short-term kit in a closed-up house is a screen, not a design document. I want a second test, or a long-term test, before I cut concrete. Real estate deals compress that timeline. You still write the limitation on the proposal.
WHO publishes a radon reference level of 100 Bq/m³, about 2.7 pCi/L [4]. Some buyers and some school specs use that tighter number. Your contract should say which target you are shooting for and how you will measure it.
No federal statute says you must mitigate at a set residential number. The Indoor Radon Abatement Act set a national long-term goal that indoor air "should be as free of radon as the ambient air outside of buildings" [7]. Outdoor air is about 0.4 pCi/L [2]. That is a goal, not a permit condition.
A few programs do create hard numbers. HUD multifamily policy and some state school rules can require action at stated thresholds. Confirm the current notice before you quote those jobs.
| Trigger | Number | Source | What it means |
|---|---|---|---|
| EPA action level | 4 pCi/L | EPA Citizen's Guide | Fix the home |
| EPA consider fixing | 2 to 4 pCi/L | EPA Citizen's Guide | Optional reduction |
| WHO reference level | 100 Bq/m³ (about 2.7 pCi/L) | WHO fact sheet | National reference many countries use |
| U.S. indoor average | 1.3 pCi/L | EPA Citizen's Guide | Typical house |
| Outdoor air | 0.4 pCi/L | EPA Citizen's Guide | Background |
What methods do mitigators actually install?
Most paid residential work is active soil depressurization. You create a negative pressure field under the slab or crawl membrane, pipe it with 3 inch or 4 inch PVC, and run a continuous in-line fan that exhausts above the eave or roof. EPA's consumer guide treats this family of systems as the common, reliable fix [3].
Sub-slab suction on poured concrete. Drain tile suction when a working perimeter tile exists. Sump pit suction when the pit is the collection point. Block wall suction on some hollow masonry foundations. Sub-membrane depressurization on dirt crawls after you lay and seal a heavy polyethylene sheet. Those are the daily tools.
House pressurization and heat recovery ventilators show up in the manuals. I rarely lead with them on a typical ranch. They cost more to run, they fight occupant behavior, and they fail the keep-it-simple test. Sealing cracks helps a soil system. Sealing alone is not a system.
Waterborne radon is a different job. Aeration or GAC on a private well is water treatment, often with its own licenses. Do not bolt a soil fan on a house whose only problem is a well and then act surprised when the post-test barely moves.
New houses can be built radon resistant with a passive stack, later activated with a fan. EPA describes those techniques separately from retrofit work [3]. If you want retrofit work, learn existing-house diagnostics first. Pressure field extension with a micromanometer will save you more callbacks than any fancy fan.
AARST's soil gas mitigation standard for existing homes (SGM-SF) is the document a lot of programs point at when they say "do it to the standard" [13]. Buy the current edition before you write warranties. Do not quote a year-old bootleg PDF.
Do you need a radon mitigation license?
It depends on the state, and the honest answer is confirm with the board. Illinois, Florida, Pennsylvania, and Kansas are examples of states that put radon work in statute or code and require a state credential to mitigate for pay [9][11][12]. Other states have no radon-specific license and lean on contractor law plus a national listing.
Illinois runs a statutory radon licensing program, and paid mitigation without that state license is a violation. Florida's section 404.056 creates a certification program for radon measurement and mitigation [11]. Kansas requires certification under the radon sections of Chapter 48 [9]. Pennsylvania runs certification through 25 Pa. Code Chapter 240 [12].
Then there is the other pile of states. Colorado has a real estate radon disclosure law, but it does not run a mitigator licensing shop the way certification states do. California has no statewide radon contractor card. You still may need a contractor license if you are contracting, plus local permits. Check radon mitigation license in California and radon mitigation license in Colorado before you assume "no radon license" means "no paper."
I would not work on a handshake in a license state. I would not ignore the contractor board in a non-license state. Two different gates. Both can shut you down.
New Jersey and a handful of other states also run strict professional programs. I am not publishing a 50-state scorecard here because legislatures rewrite these lists. If a blog gives you a count, treat it as stale. Call the contact on EPA's state page [6].
What training and exams do boards actually accept?
Most paths run through a mitigation course approved by NRPP or NRSB, then that body's exam, then whatever extra the state bolts on. EPA's public referral page points consumers at state certified people or professionals listed with NRPP or NRSB [6]. That is why those two names keep showing up.
Course length is usually a multi-day mitigation class, often on top of measurement training. Exact hours and whether you must hold a measurement credential first are handbook questions. Read the current candidate handbook. Do not trust a forum post from 2019.
Some states write their own exam or require you to hold the national credential and then apply for a state card. Illinois and Pennsylvania are not rubber stamps. They want devices, QA plans, and named responsible persons [12]. Kansas has its own application packet under the certification statute [9]. Processing times change. I will not quote a week count I cannot defend. Ask the board.
A packet like RadonPath's $149 one-time NRPP Mitigation Kit is only useful if it points you at the current handbook, the right course list, and the state add-ons. It is not a license. Nothing sold online is a license.
Waste of money: paying for a business-in-a-box that promises you can work all 50 states next month. You cannot. Also a waste: the big branding package before you have passed the exam.
If you already hold a general contractor card, do not assume the radon board will bow. In a certification state the radon credential is its own gate. In a non-certification state the contractor card may be the only gate, and the building official still wants a permit.
What does first-year paper look like?
Expect a stack. Business registration. A contractor license if your state treats this as construction. General liability insurance (ask the board and your AHJ what they want to see, do not invent a limit). Workers' comp if you have employees or if the state says so. A written QA plan if you are in a certification state. Device and lab paperwork if you also measure. Local building permits for the pipe and the fan.
Many building departments treat the fan circuit as electrical work. Some let you plug a fan into a dedicated receptacle an electrician already set. Some want the electrician on the permit. Ask before you bid. A red-tagged fan eats the job.
You also need a test protocol. Pre-test. Post-test. Occupant closed-house instructions. AARST publishes the soil gas mitigation standard used by a lot of programs [13]. You do not have to memorize the standard number to start, but you should own the current edition before you write warranties.
Keep photos. Sump before and after. Pipe routing. Fan model and serial. Manometer reading at handover. Post-test device number and placement. When a board or an angry buyer calls in month 11, that folder is the whole company.
Spend more on a decent micromanometer and a combustion appliance backup plan than on a second logo. If you depressurize a house with a rusty water heater, you can spill CO. That is not a theoretical risk. Walk the mechanicals before you turn the fan on.
License-state applications often want a responsible person, a business address, and proof of the national exam. Confirm every line with the agency that issues the card [9][11][12]. Do not copy another shop's packet and hope.
How much does a typical mitigation job cost the homeowner?
EPA's 2016 consumer guide put a common install in a range of about $800 to about $2,500, with an average around $1,200 [3]. That is EPA's published range from that guide, not a 2026 bid survey. PVC, fans, and labor have moved. Use it as a historical benchmark, then price your market.
Simple slab with a good sump: you can still land in the low end in a cheap labor market. Crawl with a full membrane, multiple suction points, or a three-story stack through finished space: you will leave that $1,200 average far behind. I would rather lose a bid than install a toy fan on a leaky membrane.
Do not copy a national average onto a mountain home with a combination foundation. Walk it. Measure the pressure field. Then write a number.
Your own first-year costs are a different spreadsheet. Course and exam. State application if any. Insurance. Permits. A saw, a rented core drill, PVC inventory, a couple of fans, sealant, a manometer, a micromanometer if you are serious. Confirm every fee with the board that charges it. I will not invent a processing charge.
Charging like a national franchise on day one is how you sit on a full van. Charging like a handyman is how you cannot pay the insurance. Price the diagnostics, the permit, the fan that will still be running in year five, and the post-test.
Homeowners will quote EPA's old average at you. Fine. Show them the crawl, the finished chase, and the extra suction point. The 2016 range was always a range [3].
What is the difference between measurement and mitigation credentials?
Measurement is testing. Mitigation is the install. They are separate credentials in the national programs and in every serious state program I have read. You can hold both. Plenty of small shops do. You still treat them as two paper trails.
If you only mitigate, you still live and die by tests. Someone has to produce a pre-number and a post-number you can defend. In license states, the tester's device list and lab are regulated [12]. Using a cousin's drugstore kit as the clearance test is how complaints start.
Conflict of interest rules exist in some states. A few want a different firm to do the post-test, or they want disclosure if you do both. Read that section. Do not guess.
EPA's public page tells consumers they can buy a test kit or hire a professional, and it tells them to hire listed or state-certified people for mitigation [6]. That split is the whole consumer story. Your website should not blur it.
If you plan to test as well, budget for a measurement course and whatever device approvals the state wants. Continuous monitors are not casual purchases in regulated states. They want calibration records. Minnesota's extension brief is a clean homeowner-facing summary of test types you will be asked to explain at the kitchen table [15].
Which states make you get a state card versus national cert only?
There is no stable public count I trust year to year, because legislatures add and rewrite programs. Treat any blog list as stale the day it ships. Confirm with the state radon contact [6] and with the statute.
States with a real radon professional program (examples, not a complete list) include Illinois, Florida, Pennsylvania, and Kansas [9][11][12]. Those programs have named acts or code chapters. You apply to that agency. A national wallet card is an input, not the finish line.
States without a radon-specific license still have contractor boards, permit desks, and consumer protection statutes. How to start radon mitigation in Arizona is a different animal from radon mitigation license in Alabama. Read the one that matches your truck plates.
Zone maps do not equal license maps. EPA's Map of Radon Zones tells you where high radon is more common. It does not tell you who may install a fan [14]. Zone 1 counties still might have zero state radon card. Zone 3 counties can sit inside a strict certification state.
If you work two states, keep two folders. Reciprocity is uneven and sometimes imaginary. I have watched people assume a neighboring state "pretty much matches." It did not.
What equipment should you actually buy first?
Buy diagnostics and seal, not merch. A good micromanometer, smoke or a theatrical fog bottle, a drill and a core bit, PVC and fittings in the diameters your standard uses, polyurethane caulk, sump lids you can seal, and two fan models you understand. Then a U-tube manometer for every system you leave behind.
Skip the thermal camera in month one. Skip the custom trailer wrap. A cheap fan that cannot move a marginal pressure field will generate more refunds than it saves.
For crawls, budget membrane, tape that actually sticks in January, and time. The membrane is the system. The fan is the motor. A sloppy seam is a callback.
Electrical bits: dedicated receptacle, disconnect if the code official wants one, exterior-rated flex, and a weather cap that does not dump water into the fan. Confirm local code. I am not your AHJ.
If you also measure, that is a separate cart. Do not mix job-box charcoal canisters with your lunch.
I would rather have three fans on the shelf and a spare impeller than a leased billboard. Fans fail on Friday nights. Your phone will ring.
Own the current mitigation standard before you buy exotic fittings [13]. Most houses take common Schedule 40 and a fan sized to the pressure field you measured, not the one a catalog promised.
What gets people in trouble in year one?
Unpermitted work. Depressurizing a house and spilling a combustion appliance. Calling a sealed crack mitigation. Skipping the post-test. Working in a license state on a national card alone. Promising zero radon. There is no honest zero. Outdoor air still has some [2].
Also: cutting a chase through a finished kitchen without a change order. Mounting a fan in a wet crawl where it will drown. Exhausting under the soffit so the gas re-enters a window. Those are craft failures, and they show up on review sites faster than any board complaint.
Document the closed-house conditions you asked for. If the owner runs the whole-house fan during the post-test, the number is junk. Write that down before the argument.
Insurance claims and board complaints both start with a number that went back up. Systems need the fan running. Tell people that in writing. Stick a manometer they can read. If the liquid is flat, the system is off.
License-state complaints often cite work done for pay without the card [11][12]. That is an easy case for the agency. Do not be that case.
Combustion safety is the one that should scare you more than a fine. A soil fan that tightens a leaky basement can pull a water-heater draft backward. Check appliances. Leave CO advice in the handover packet. I would walk away from a house I cannot make safe.
Where should you confirm the rules before you take a job?
Start with the state radon program contact on EPA's local information page [6]. Then the statute or code chapter if one exists. Then the contractor licensing board. Then the city or county building department for the address on the proposal. That order has saved me from stupid bids.
If you want a packet that already maps NRPP steps next to state add-ons, RadonPath publishes a $149 one-time NRPP Mitigation Kit at /start. Use it as a checklist, then still open the board's own PDF. We are an independent publisher, not a law firm and not a mitigation company. The board's PDF wins.
For a state-by-state paper path, keep going through the state guides, including how to start radon mitigation in Connecticut and how to start radon mitigation in California. Rules move. Confirm the date on every form you download.
EPA's zone map is fine for deciding where demand is likely. It is useless as a license map [14]. The Citizen's Guide and the consumer reduction guide are still the documents your customers will quote at you [2][3]. Read both so you are not surprised.
Nobody has a perfect live database of every county permit quirk. The closest honest method is still a phone call to the building department on the job address, plus the state contact EPA publishes [6].
Frequently asked questions
What is radon mitigation?
It is the building work that lowers indoor radon, usually by pulling soil gas from under a slab or crawl membrane with a sealed pipe and a continuous fan. It is not an air filter. EPA treats active soil depressurization as the common, reliable residential method. Water treatment for well radon is a separate trade.
How do you start radon mitigation?
Read the state radon statute if one exists, then the contractor board, then the local building department. Take a course and exam NRPP, NRSB, or the state will accept. Get the insurance and permits the AHJ asks for. Then bid a simple slab house. There is no single national license that lets you skip those steps.
Is radon mitigation the same as radon testing?
No. Testing (measurement) produces a number. Mitigation is the install that tries to drop that number. National programs and license states treat them as separate credentials. You can hold both, but some states add conflict-of-interest rules if one shop does the clearance test on its own system. Read that section before you bundle.
How long does a typical install take?
A simple slab ranch with a usable sump is often a one-day install plus the post-test window. Crawls, combination foundations, and finished chases run longer. Nobody has a clean national time study I trust. Walk the house. If a sales script promises every job in four hours, that script is selling, not estimating.
Can a homeowner install their own radon system?
Some states allow owner-occupant DIY and still ban paid work without a credential. EPA still steers the public toward listed or state-certified contractors. DIY fails usually come from a weak pressure field, a fan that re-entrains, or no post-test. If you are building a shop, do not coach unpermitted paid work around a license statute.
What is active soil depressurization?
A sealed suction point under the slab, drain tile, sump, or crawl membrane, piped to a continuous fan that vents outdoors. The fan keeps the soil side slightly negative so radon-laden gas goes up the stack instead of into the house. It is the method EPA's consumer guide treats as the usual residential fix.
Do you need both a contractor license and a radon credential?
In a radon-license state you often need both, because one card is radiation-program paper and the other is permission to contract. In a state with no radon card you may still need a contractor registration and a building permit. Confirm both gates. A national NRPP or NRSB listing alone is not a contractor license.
When should you retest after mitigation?
After the system has been running and the house is back on closed-house conditions. Short-term post-tests are the common clearance tool. Follow the protocol you named in the contract and the current AARST measurement and mitigation standards. I would not call a job done on a same-afternoon number taken while doors are open.
What is the difference between NRPP and NRSB?
They are the two national proficiency programs EPA names when it tells the public how to find a professional. States pick one, both, or neither, and some still require their own card on top. Fees, course lists, and renewal rules differ. Confirm which listing your board will actually accept before you pay for a class.
Does every state license radon mitigators?
No. Illinois, Florida, Pennsylvania, and Kansas are examples that do, by statute or code. Many states do not issue a radon-specific card and rely on contractor law plus NRPP or NRSB. Lists change. Confirm with the state contact on EPA's page and with the statute, not with a five-year-old blog table.
Is there a federal law that forces mitigation at 4 pCi/L?
No. EPA's 4 pCi/L action level is guidance. The Indoor Radon Abatement Act set a long-term national goal that indoor air should be as free of radon as outdoor air, not a residential mandate at 4. Some HUD and school programs create their own triggers. Those are program rules, not a universal federal install order.
How much should a new shop charge for a job?
Price the house you walked, not EPA's 2016 average of about $1,200. That guide's published range was about $800 to $2,500 and is a benchmark, not your market. Include diagnostics, permit, fan quality, membrane labor, and a real post-test. Underpricing a crawl to win the first ten jobs is how you fund other people's repairs.
Why does every finished system get a U-tube manometer?
So the occupant can see that the fan is pulling. Flat liquid means the system is off or the tube is dead. Inspectors, buyers, and you in month eleven all look at that tube first. It is cheap. Leaving a house without one is sloppy, and it makes every callback argument harder.
Are crawl space systems different from slab systems?
Yes. A crawl job is mostly a sealed membrane plus suction under that sheet. A slab job is mostly a cored suction pit or a sealed sump. Crawls fail at seams, plumbing penetrations, and drowned fans. Slabs fail at unsealed sumps and short pressure fields. Bid the membrane hours honestly or you will hate crawls.
Sources
- U.S. EPA, Health Risk of Radon: EPA estimates about 21,000 U.S. lung cancer deaths per year from radon.
- U.S. EPA, A Citizen's Guide to Radon (2016): Action level of 4 pCi/L, consider fixing at 2 to 4, average indoor 1.3 pCi/L, outdoor 0.4 pCi/L, about 1 in 15 homes elevated, and the verbatim fix-your-home sentence.
- U.S. EPA, Consumer's Guide to Radon Reduction (2016): Soil depressurization as the usual residential method, radon-resistant new construction techniques, and the published about $800 to $2,500 cost range with an average around $1,200.
- World Health Organization, Radon and health fact sheet: WHO reference level of 100 Bq/m³ and radon causing an estimated 3 to 14 percent of lung cancers.
- National Cancer Institute, Radon and Cancer fact sheet: Radon is the second leading cause of lung cancer in the United States after smoking.
- U.S. EPA, Find a Radon Test Kit or Measurement and Mitigation Professional: EPA directs the public to state-certified professionals or those listed with NRPP or NRSB, and publishes state radon contacts.
- 15 U.S.C. § 2661, National goal (Indoor Radon Abatement Act): Statutory national long-term goal that indoor air should be as free of radon as ambient outdoor air.
- Kansas Revisor of Statutes, K.S.A. 48-16a01 (Kansas Radon Certification Law): Kansas has a statutory radon certification law for radon professionals.
- Florida Statutes § 404.056 (2023): Florida statute creates certification requirements for radon measurement and mitigation.
- Pennsylvania Code, 25 Pa. Code Chapter 240 (Radon Certification): Pennsylvania certifies radon mitigators and testers under Chapter 240, including device and QA requirements.
- AARST Consortium, ANSI/AARST SGM-SF-2023 Soil Gas Mitigation Standard: SGM-SF is the named soil gas mitigation standard for existing homes used by many programs.
- U.S. EPA, EPA Map of Radon Zones: EPA zone map shows where higher indoor radon is more common; it is not a licensing map.