Overview & Radon Maps
California has numerous counties with moderate to high radon levels. Because radon levels have the potential to be high nearly everywhere in the world, the International Radon Council recommends testing your home for radon no matter where you live. However, residents who live in high radon zone areas need to be particularly deliberate in testing their homes.
Average indoor radon level potential is likely to be 4.0 pCi/L or greater.
Average indoor radon level potential is likely to be between 2.0 to 4.0 pCi/L.
Average indoor radon level potential is likely to be less than 2.0 pCi/L.
When is Mitigation Necessary?
The World Health Organization recommends that buildings with radon levels of 2.7 pCi/L or greater be mitigated.
The Environmental Protection Agency recommends that buildings with radon levels of 4.0 pCi/L or higher be mitigated. For buildings with radon levels greater than 2.0 but less than 4.0 pCi/L, the EPA recommends considering mitigation.