Every company here employs at least one professional holding a current certification with the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB), the two bodies that certify radon work in the US. 2,830 companies across 51 states, grouped by what each one is actually certified to do.
with at least one currently certified professional
certified for radon mitigation
certified for radon measurement
Measurement and mitigation are different certifications, and neither registry sorts its directory that way. If your test came back high and you want it fixed, you need a company certified for mitigation. If you only want to find out where you stand, measurement is enough, and a long-term test kit you place yourself is cheaper still. Some listings are laboratories that analyze kits and never visit a house.
Certification means someone was trained and tested to a national standard. It does not tell you what a company is like to deal with. Get more than one quote, the same as any other trade.
Full company lists are published state by state. Iowa, Illinois and Minnesota are live now. The counts below are for every state in the registries, so you can see the size of each one before its page exists.
| State | Companies | Certified for mitigation |
|---|---|---|
| Alabama | 24 | 8 |
| Alaska | 8 | 2 |
| Arizona | 27 | 8 |
| Arkansas | 7 | 3 |
| California | 119 | 18 |
| Colorado | 442 | 159 |
| Connecticut | 67 | 34 |
| Delaware | 7 | 4 |
| District of Columbia | 4 | 0 |
| Florida | 45 | 10 |
| Georgia | 54 | 15 |
| Hawaii | 2 | 1 |
| Idaho | 18 | 9 |
| Illinois | 70 | 19 |
| Indiana | 199 | 56 |
| Iowa | 25 | 11 |
| Kansas | 33 | 12 |
| Kentucky | 89 | 34 |
| Louisiana | 2 | 0 |
| Maine | 20 | 6 |
| Maryland | 101 | 21 |
| Massachusetts | 71 | 20 |
| Michigan | 73 | 41 |
| Minnesota | 53 | 26 |
| Mississippi | 1 | 0 |
| Missouri | 58 | 16 |
| Montana | 25 | 17 |
| Nebraska | 14 | 5 |
| Nevada | 28 | 3 |
| New Hampshire | 31 | 18 |
| New Jersey | 39 | 8 |
| New Mexico | 16 | 7 |
| New York | 123 | 40 |
| North Carolina | 92 | 39 |
| North Dakota | 13 | 10 |
| Ohio | 65 | 19 |
| Oklahoma | 11 | 2 |
| Oregon | 37 | 13 |
| Pennsylvania | 69 | 18 |
| Rhode Island | 35 | 7 |
| South Carolina | 18 | 7 |
| South Dakota | 13 | 8 |
| Tennessee | 60 | 29 |
| Texas | 45 | 7 |
| Utah | 36 | 28 |
| Vermont | 18 | 8 |
| Virginia | 268 | 46 |
| Washington | 24 | 7 |
| West Virginia | 46 | 10 |
| Wisconsin | 75 | 48 |
| Wyoming | 10 | 7 |
The listings come from the public directories of the two US radon certification bodies: NRPP and NRSB. Certified individuals are grouped into the company they list, and each company is tagged with the services its people are certified for, taken from the certifications the registries publish rather than from anything the company says about itself.
Phone numbers and websites appear only where a registry publishes them. We do not fill the gaps from third-party business data, because matching on a company name gets it wrong often enough to put one firm's phone number on another firm's listing.
Every certified company is listed free, in alphabetical order, whether or not it knows this page exists. Certifications expire, companies move and registries lag. If something here is wrong or out of date, tell us and it gets fixed.
Registries read 2026-09-01. Some states license radon professionals themselves on top of NRPP and NRSB, so a company can be legitimate in your state without appearing in either national registry.