The Indoor Radon Program, within the Environmental Management Branch, seeks to reduce the health risk from radon exposure by increasing awareness, identifying areas of high radon potential, and encouraging all Californians to test their homes for radon, fix their homes if they have a radon problem, and build new homes radon-resistant. Test. Fix. Save a Life.

​Interactive California Radon Potential Map

The California Geological Survey has released an interactive web map providing radon potential information for areas of California with completed radon potential maps. Downloadable GIS data for each study area can now be downloaded through the interactive map.

Statewide Indoor Radon Potential Report

The California Geological Survey has released Special Report 247: California Indoor Radon Potential (2022), which addresses the radon potential throughout the state of California. The statewide report, and all regional radon potential reports, are available upon request directly from the California Geological Survey.

Information Bulletin for Radon Professionals:​ 100% Ground Contact Testing Requirements for Multifamily Housing

The California Health and Safety Code (HSC) is the prevailing regulatory statute that applies to the control of radon in California including but not limited to requirements for performing radon measurement, mitigation, and laboratory analysis. HSC Section 106780 requires that no person may provide radon services for the general public, or represent or advertise that he or she may provide radon services unless that person meets the provisions of HSC, Section 106780, which includes successfully completing the National Radon Proficiency Program (NRPP) or the National Radon Safety Board Certified Radon Professional Program (NRSB). Both programs require their certified individuals to follow the American National Standards Institute, American Association for Radon Scientists and Technologists (ANSI-AARST)​ standards, which includes the requirements for 100% ground contact testing for multifamily housing and testing 10% upper floor units. ​Visit the NRPP and NRSB websites to view information regarding their certification requirements. ​​​