EPA radon zone for an address or county. Perfect for: 'radon zone for an address', 'EPA radon potential for a county', 'is this a high radon area', 'radon zone 1 2 or 3 lookup'. Returns the EPA Map of Radon Zones county designation (1/2/3) for a point or explicit state+county, with a Zone 1 high-potential watch item and provenance. National. County-potential context only -- not a measured indoor radon reading. Charge-free when geocoding fails or the county is not matched.