Hiring a Certified Radon Mitigator: Questions to Ask

Before hiring anyone to reduce the radon in your home, confirm they’re certified by a recognized national program — the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB) — or licensed by your state where that’s required, and ask for proof. From there, the questions that matter most are whether they’ll install the system to national standards, carry liability insurance, put a written guarantee in place to bring your level below 4 pCi/L, and arrange a follow-up test to confirm it worked. Radon mitigation is a technical job, and because you can’t see or smell the gas, you can’t tell by looking whether a system is actually working. The right questions upfront are how you avoid paying for one that isn’t.

This guide explains why certification carries real weight, then walks through the specific questions to ask a mitigator and what a good answer sounds like.

Why hiring a certified mitigator matters

Radon is a naturally occurring radioactive gas that seeps up from soil and rock and collects indoors, and the U.S. EPA identifies long-term exposure as the second-leading cause of lung cancer in the United States. It’s measured in picocuries per liter (pCi/L); EPA recommends fixing a home at or above 4 pCi/L and considering action between 2 and 4 pCi/L. Reducing it isn’t a matter of sealing a few cracks. The standard fix, active soil depressurization, uses a fan and a vent pipe to pull soil gas from beneath the foundation and route it above the roofline, and designing that system well depends on diagnostic testing, correct fan sizing, proper pipe routing, and sealed exhaust placement.

When any of that is done poorly, the consequences aren’t obvious. A system can run, hum along, and still leave your radon above the action level. Poorly placed exhaust can let radon re-enter the home, and a system that changes the pressure balance of a house can, in some cases, affect how combustion appliances vent. None of these problems announce themselves, because radon is invisible and odorless. That’s the core reason certification matters here more than in many home trades: you’re relying on the installer’s competence to solve a problem you can’t personally verify by eye.

Certification through NRPP or NRSB means the professional has been trained and tested against the national consensus standards for radon work — the ANSI/AARST standards — and is accountable to a credentialing body. Many states add their own licensing or registration requirements on top. Checking for that credential is the single most reliable filter you have. Our radon mitigation guide explains how these systems are supposed to work, which makes it easier to judge the answers you get.

Questions about credentials and coverage

Start by confirming the basics that separate a qualified professional from a general handyman.

• Are you certified by NRPP or NRSB, and can I see your certification? A qualified mitigator will show you a current credential and ID number without hesitation. You can also verify it directly through the certifying program’s online listing rather than taking the card at face value.
• Does my state require a license or registration, and do you hold it? Many states regulate radon professionals; some don’t. Where your state has requirements, the contractor should meet them. If your state doesn’t regulate the trade, national certification becomes even more important as your assurance of competence.
• Do you carry liability insurance, and are you bonded? EPA advises confirming proof of liability insurance and bonding before work begins. This protects you if something is damaged or goes wrong during installation.
• Will the system be installed to ANSI/AARST standards? The answer should be a clear yes. These are the recognized national standards for how a mitigation system is designed, installed, and labeled, and following them is what separates a code-quality system from an improvised one.

Questions about the work itself

Once credentials check out, focus on how the contractor approaches your specific home. A good mitigator diagnoses before they quote.

• What method do you recommend for my home, and why? The answer should reference your foundation type and, ideally, some diagnostic measurement rather than a one-size-fits-all pitch. Active soil depressurization is the most common approach, but the right design depends on how your home is built.
• Can you provide references and before-and-after test results from past jobs? EPA suggests treating this like any home repair: ask for references, contact a few, and ask whether they were satisfied. Before-and-after radon numbers from prior work show the contractor’s systems actually bring levels down.
• Where will the fan and exhaust be located? Placement affects both performance and whether radon can re-enter through windows or other openings. A certified professional can explain how their planned routing meets the standard’s requirements.
• How will the system be labeled and monitored? Systems should include a simple warning device or gauge that shows the fan is working, and the pipe should be labeled so anyone in the home later understands what it is.

Questions about guarantees, testing, and cost

This is where a professional job is defined on paper. Get the commitments in writing before work starts.

• Will you guarantee in writing that the system brings my level below 4 pCi/L? A reputable mitigator will provide a written guarantee to reduce radon below the action level, and stand behind it if the first attempt falls short. Ask what the guarantee covers, how long it lasts, and whether it transfers to a future buyer.
• Will there be a post-mitigation test, and who performs it? Confirming the fix is not optional. EPA recommends a post-mitigation test within 30 days of installation. Having an independent tester — someone other than the installer — run that test removes any conflict of interest, since the person confirming the work isn’t the person who was paid to do it.
• What is the total cost in writing, including the timeline, permits, and cleanup? A written contract should spell out the full price, who pulls any required permits, the schedule, and who handles cleanup, so there are no surprises later.
• What will the system cost to run and maintain? The fan runs continuously and uses electricity, and fans have a service life. Ask about the fan’s warranty and expected operating cost. The cheapest bid isn’t always the cheapest system to own, since a marginal design can cost more to run or need earlier repair.

Prices vary widely by region, foundation type, and how complex your home is, so compare more than one estimate rather than anchoring on a single number or automatically taking the lowest. For a printable version of these questions to bring to each estimate, our radon contractor checklist lays them out in order.

After the system is installed

Hiring well doesn’t end at installation. The post-mitigation test is what tells you the money was well spent, and it should show your level is below the action level under normal living conditions. Keep the contract, the guarantee, and the test results together in case you ever sell the home, since buyers and their agents often ask for them.

Radon levels and equipment both change over time, so plan to retest every couple of years, and have the system checked if the warning device ever indicates the fan has stopped. A certified tester can retest and inspect the system at the same time. Our guide to radon testing covers how to run that follow-up test correctly.

Frequently asked questions

Why can’t I just hire a general contractor or handyman?
Radon mitigation is a specialized field with its own national standards and diagnostic methods. A system that looks finished can still leave radon above the action level, and because the gas is invisible and odorless, you can’t judge the result by eye. A certified mitigator is trained to design and verify the system to ANSI/AARST standards, which is the assurance a general contractor typically can’t offer.

What’s the difference between NRPP and NRSB certification?
Both are national credentialing programs that EPA recognizes for radon professionals, and both require training and testing against recognized standards. Either credential indicates a qualified professional. Some states also require their own license or registration on top of national certification, so it’s worth confirming your state’s specific requirements as well.

Should the same company that installs the system also test it afterward?
It’s common, but having an independent tester perform the post-mitigation test removes a potential conflict of interest, since the party confirming success isn’t the one who was paid to install the system. Many homeowners have the professional who did the original testing perform the follow-up. Either way, a test within 30 days of installation is how you confirm the system actually works.

What should a mitigation guarantee include?
A solid written guarantee commits to bringing your radon below 4 pCi/L and describes what happens if it doesn’t — typically the contractor adjusting or extending the system at no extra cost. Ask how long the guarantee lasts, exactly what it covers, whether the fan carries its own warranty, and whether the guarantee transfers to a future owner if you sell.

What this means when you’re ready to hire

The homeowner who asks a handful of pointed questions — about certification, insurance, standards, a written guarantee, and an independent follow-up test — ends up with a system that measurably lowers radon and paperwork that proves it. Because you can’t verify the result with your own senses, those questions are your verification. Confirm the credential, get the commitments in writing, and insist on a post-mitigation test. To connect with a certified radon mitigation professional in your area and compare estimates, request a free quote.

Sources and further reading

• U.S. Environmental Protection Agency, Consumer’s Guide to Radon Reduction: How to Fix Your Home
• U.S. Environmental Protection Agency, How Can You Find a Qualified Radon Service Provider in Your Area?
• National Radon Proficiency Program, Homeowners and Buyers FAQs
• National Radon Safety Board, National Radon Safety Board
• National Radon Program Services (Kansas State University), Radon Certification Programs
• U.S. Environmental Protection Agency, Health Risk of Radon

This article is for general educational purposes and is not medical advice. Long-term radon exposure is associated with an increased risk of lung cancer, but individual risk depends on many factors. Reducing elevated radon can lower future exposure; it cannot undo exposure already received. For guidance on your home, consult a certified radon professional, and for health questions consult a qualified medical provider.