Finding a qualified radon contractor takes a bit more than a general web search — here’s a practical approach.
Radon work sits in an unusual regulatory position. It is a specialised trade with national certification schemes, and in many states anyone may still legally perform it. Which of those two facts applies where you live determines how much of the vetting falls to you.
- NRPP and NRSB directories are a reliable starting point for finding certified contractors.
- State radon programs often maintain their own approved contractor lists.
- Verify certification numbers directly rather than trusting a contractor’s self-reported credentials.
- Ask about local experience with your area’s specific foundation and soil conditions.
Where to Search
The NRPP and NRSB both maintain public directories of certified professionals searchable by location — this is a more reliable starting point than general contractor listing sites, since it filters directly for verified radon-specific certification.
The two national certification bodies are the National Radon Proficiency Program and the National Radon Safety Board, and both publish searchable directories of certified individuals by location. Searching those directly rather than a general contractor listing filters for the qualification that matters at the first step instead of the last. It is worth knowing that measurement and mitigation are separate certifications, so a professional certified to test is not necessarily certified to install, and for some purposes you specifically want two different parties.
Your state radon programme, normally sitting within the state health department, is the other authoritative starting point and is the one that tells you which rules apply locally [1]. Some states license radon contractors and maintain a list of approved firms. Others require no licence at all, in which case national certification is the only credential in play and verifying it becomes entirely your responsibility. The same office is usually the source for free or discounted test kits, so the visit answers two questions at once.
Your state radon program (usually under the state health department) often maintains its own list of state-approved or licensed contractors as well, particularly useful in states with specific licensing requirements.
Vetting Candidates
Once you have a shortlist, verify certification numbers directly on the NRPP/NRSB site, check for online reviews specific to radon work (not just general contractor reviews), and confirm liability insurance.
Verify certification at the source rather than accepting a logo. Ask for the certification number and check it in the NRPP or NRSB directory yourself, confirming that it is current and that it covers mitigation rather than measurement only. Certification lapses, and a badge on a website or a vehicle is not evidence that it is in force today. Confirm general liability insurance as well, and be aware that a state licence, where one exists, is a separate credential from national certification rather than a substitute for it.
The most informative question to ask has nothing to do with credentials. Ask how the contractor will determine where the suction points go and how many there will be. A good answer describes a site visit and a sub-slab communication test, drilling a point, applying vacuum and reading the pressure response elsewhere in the slab to see how far the field extends. An answer that prices from square footage or over the phone without any diagnostic step is a design by assumption, and that assumption is the most common reason a completed system fails its retest.
Get at least three quotes, asking each the same set of questions (see our piece on getting multiple quotes) so you’re comparing consistent information across candidates.
Local vs. Regional Contractors
A contractor with specific experience in your area’s typical foundation types and soil conditions can be valuable — ask directly how many similar jobs they’ve completed nearby, since regional experience with local geology and construction norms is a meaningful (if less formal) qualification.
Local experience is a real qualification for a specific reason. Sub-slab depressurization depends on how readily a pressure field spreads through the material under the slab, which is a function of soil and fill, and on how the building is constructed, which follows regional convention. A contractor who works constantly in your area has calibrated expectations for the fill under local slabs and the footing layouts local builders use. Asking how many similar houses nearby they have mitigated is a fair question and the answer is informative.
Set that against the questions that decide the outcome regardless of who answers them, which are whether a diagnostic test is performed, whether the discharge terminates above the roofline and clear of openings, whether the fan sits outside the conditioned space, and whether a post-installation retest is included. Any competent certified mitigator can satisfy those. A firm that both installs and tests may also be restricted from doing both in a transaction in some states, since it has an interest in the finding, so an independent confirming test is worth arranging on its own account.
What Belongs in the Contract Before You Sign
The most important clause is the one defining what success means. A warranty covering the fan against failure is a hardware warranty. A warranty committing the contractor to achieve a reduction below the action level, and to return and modify the system at their cost if the post-installation test does not, is a performance guarantee. These are very different promises and are frequently described in similar language. Whether the design risk sits with you or with the installer is decided by which one the contract contains.
Have the specifics written down rather than discussed. The number and location of suction points, the fan model and its mounting position, where the pipe discharges, and whether a post-installation retest is included and who performs it should all appear in the document. The fan position in particular is worth seeing in writing, because the pipe downstream of the fan is under positive pressure and a leak in that section inside the house would push concentrated soil gas indoors. Attic, unconditioned garage or exterior mounting is standard practice and should not be a variable.
Ask for the paperwork you will need years from now while it is easy to obtain: the pre-mitigation result, an as-built description of the system, the fan model and installation date, and the commissioning retest. That set is what a future buyer’s inspector will ask about, and it is far simpler to collect at handover than to reconstruct later. If the mitigator also performed the confirming test, consider an independent retest as well, since a result from a party with no financial interest in it is the stronger document.
FAQ
Is a general contractor directory site reliable for finding radon mitigators?
It can be a starting point, but cross-check any candidate against the NRPP or NRSB certification directories for verified radon-specific credentials.
Are radon contractors licensed everywhere?
No. Some states license radon professionals and publish a list of approved firms, and others have no licensing requirement at all. Where no state licence exists, national certification through the NRPP or NRSB is the only credential, and verifying it is entirely on you. Check your state radon programme to find out which applies.
What is the most revealing question to ask a prospective mitigator?
How they will decide the number and placement of suction points. A good answer involves a site visit and a sub-slab communication test. Pricing from square footage or over the phone with no diagnostic step means the design is an assumption, which is the most common cause of a system that fails its retest.
Is a warranty on the fan the same as a warranty on the result?
No, and the difference is significant. A hardware warranty covers fan failure. A performance guarantee commits the contractor to bring the level below the action level and to return and modify the system at their own cost if the retest does not confirm it. Check which one the contract actually contains.
Always independently verify certification rather than relying solely on a contractor’s self-reported credentials or a general review site’s badge system.
References
- Find a Radon Test Kit or Measurement and Mitigation Professional. U.S. Environmental Protection Agency
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
