San Francisco County
San Francisco County is classified by the EPA’s 1993 Map of Radon Zones as Zone 2, indicating moderate radon potential. The predicted average indoor radon screening level is between 2 and 4 pCi/L. While below the EPA action level, many individual homes in Zone 2 areas test above 4 pCi/L. The EPA recommends testing all homes regardless of zone.
San Francisco County falls into EPA Radon Zone 2, indicating moderate radon potential with predicted indoor screening levels between 2 and 4 pCi/L. It is one of 29 Zone 2 counties in California (50% of the state's 58 counties). That is a predicted screening level from the EPA's 1993 map, not a measured average, and many individual homes in Zone 2 areas still test above it. Factors like foundation type, soil conditions, and ventilation can push radon levels higher in specific homes.
Test for radon in San Francisco County
EPA Zone 2 means moderate radon potential (2-4 pCi/L predicted average). The EPA recommends testing every home; many individual Zone 2 homes test above 4 pCi/L.
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What This Means for San Francisco County
Should You Test?
Yes. While Zone 2 has moderate predicted levels, many individual homes still test above 4 pCi/L. Home-specific factors like foundation type, soil permeability, and ventilation matter as much as the zone classification. A $15–$30 short-term test kit is the easiest way to find out.
Real Estate
Consider requesting a radon test during the home inspection process. If levels are elevated, mitigation systems are effective and relatively affordable.
New Construction
Radon-resistant new construction (RRNC) is recommended for new homes in Zone 1 and Zone 2 areas, so if you are building here, ask your builder to include it. These features add $350–$500 to construction costs and include a sub-slab gas collection layer, vapor barrier, sealed cracks, and a vent pipe to the roof. Much cheaper to install during construction than to retrofit.