US Radon Risk Map by County
Every US county, colored by its EPA Radon Zone. Radon is a natural, radioactive gas and the second-leading cause of lung cancer — the EPA recommends that every home be tested regardless of zone.
Check your area
Search your city for its radon zone, the state average, and testing guidance.
How to read this map
The EPA assigns each US county to one of three radon zones based on predicted average indoor radon levels. Zone 1 counties have a predicted average above 4 pCi/L (the EPA action level), Zone 2 from 2–4 pCi/L, and Zone 3 below 2 pCi/L. Zones describe the county average — individual homes vary widely, so the EPA recommends testing every home, even in Zone 3.
Source: EPA Map of Radon Zones. See our methodology for details. Found an error? Let us know via our about page.