Appendix C

Radon credentials by state

This table covers all 50 US states and the District of Columbia. We have confirmed the radon credentialing body for 16 of them: 11 publish a list with credential numbers that this site imports monthly, and 5 credential radon work but publish no such list. For the other 35 we have not confirmed whether a state credential is required. Each row links to the page where you check a number yourself.

Last verified September 5, 2026. Methodology

§ C.1

How to read this table

Three tiers, and the difference matters. Roster imported here means the agency publishes a current list with credential numbers and we re-check it monthly. Credentialed, no public roster means the state credentials radon work but publishes no list we can import, so listings for that state are national NRPP or NRSB certifications, which are not the state credential. Not confirmed by us means exactly that: we have not established whether the state requires a credential. It does not mean none is required. We do not guess at state law.

§ C.2

What this table is not

It is not legal advice and not a claim about what any state requires. It records which agency we confirmed, where the public verification page is, and how many current listings this site holds. Where we could not confirm a program, the row says so rather than filling the gap with the national certification bodies, which credential people nationwide and have no authority over state law. Read the methodology for how each source is imported.