Appendix C

Radon credentials by state

This table covers all 50 US states and the District of Columbia. We have established the position in 20 of them: 11 publish a list with credential numbers that this site imports monthly, and 7 credential radon work but publish no such list. In 2 more, the state issues no credential of its own but its statute requires an NRPP or NRSB listing, and we cite that statute. For the other 31 we have not confirmed whether a state credential is required. Each row links to the official page or statute it rests on.

Last verified September 8, 2026. Methodology

§ C.1

How to read this table

The tiers differ in ways that matter. 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. NRPP or NRSB listing required by state law means the state issues no radon credential itself, but its own statute requires the national listing. Those rows carry the citation and the statute’s own words. Not confirmed by us means exactly that: we have not established whether the state requires a credential. It does not mean none is required. Where a state agency says in as many words that it does not license radon work, that row quotes the agency and stays in this tier, because we publish their statement rather than our conclusion. 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.