Chapter 04 — The California file

Radon testing & mitigation in California

Current CA CDPH credentials from the official California roster. The file does not publish city or county. We do not invent neighborhoods. Source: CA CDPH.

Latest credential check August 29, 2026. Methodology Individual record dates may be earlier.

229current listings

217testing

12mitigation

§ 4.3

How to verify a radon credential in California

CA CDPH certifies radon work in California and publishes a list we import monthly. Match the name and credential number on the official page before you hire.

Official CA CDPH verification page · All fifty states · reviewed September 8, 2026

§ 4.4

Questions about radon credentials in California

Does California license radon testers and mitigators?

CA CDPH certifies radon work in California and publishes a current list with credential numbers. This site imports that list and re-checks it monthly. 229 current California listings appear here as of August 29, 2026.

How do I verify a radon credential in California?

Open the CA CDPH lookup at https://www.cdph.ca.gov/Programs/CEH/DRSEM/Pages/EMB/Radon/Certified-Radon-Services-Providers.aspx, search the name, and match the credential number digit for digit. Status can change between our monthly check on August 29, 2026 and the day you hire. If the official page disagrees with this directory, the official page is right.

Is an NRPP or NRSB certification enough in California?

California issues its own radon credential through CA CDPH, so a national NRPP or NRSB certification is not a substitute for it. Every California listing on this site shows the CA CDPH number, not a national one.