Radon testing in California

radon.directory lists 7 radon testers in California in 7 cities. Each one says on its own website that it tests for radon and has an open Google Business Profile, checked in October 2026.

Of the 7 businesses listed: 3 other businesses that test for radon; 2 radon companies that test and fix radon; 1 home inspector; 1 radon testing company. Radon specialists often also fix high levels; home inspectors usually test during a home sale.

The EPA suggests your state radon program as the place to find qualified professionals, and says states list only providers credentialed by a state license or by one of the two national programs, the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Ask a tester which credential they hold. Source.

The EPA says to fix your home if the radon level is 4 pCi/L or more, and to consider fixing it between 2 and 4 pCi/L. Source.

A short-term test takes a few days and is a quick way to screen a home. A long-term test runs at least 91 days and shows your average level over the year. A high short-term result is usually followed by a second test before deciding to fix. Source.

Yes. The EPA notes that test kits are sold online and in home improvement stores, and that some states offer free or discounted kits. A professional test is common when buying or selling a home. Source.