3,143 counties

Radon zones by state and county

1,074 US counties are EPA radon zone 1, where the predicted average indoor level is above EPA's 4 pCi/L action level. Pick your state to see every county.

Counties in EPA radon zone 10%1% to 18%19% to 40%41% to 62%63% or moreNo data

Smaller states:Connecticut Delaware Maryland Massachusetts New Hampshire New Jersey Rhode Island Vermont

What the zones mean

EPA radon zones describe counties, not houses. Zone 1 counties have a predicted average indoor level above 4 picocuries per liter (pCi/L), Zone 2 between 2 and 4, Zone 3 below 2. Homes with high levels are found in every zone, which is why EPA recommends that every home be tested, and fixed at 4 pCi/L or above.

Zone 1: above 4 pCi/L predictedZone 2: 2 to 4 pCi/LZone 3: below 2 pCi/L

Test, then decide

A $15-25 kit answers the question in days. If you are at 4 pCi/L or above, a mitigation system usually costs $800-2,500.

Radon testing guide

Source: EPA Map of Radon Zones.