How much radon risk does my county have?

All 3,144 US counties. Start typing.

The EPA scores every US county on predicted indoor radon levels, zone 1 to 3, from soil geology and measured test results. This shows you your county's zone, its rank among all 3,144 counties, and what the level actually means for testing your home. Free, no email.

EPA's three radon zones, and what each means for your next move
Zone	Predicted average	Counties	What to do
Zone 1	above 4 pCi/L	1,065	Test first. Above EPA's action level on average - mitigation is common here.
Zone 2	2 to 4 pCi/L	1,032	Test anyway. Close enough to the action level that many homes exceed it.
Zone 3	below 2 pCi/L	1,031	Still test once. Lower odds, not zero - EPA has no zone with a safe skip.

Read this before you rely on it

A county's EPA zone is a predicted average across the whole county from a 1993 geologic and radioactivity assessment - not a reading for any one house. EPA's own guidance is to test every home regardless of its county's zone, including Zone 3. A test kit costs about $15 and a lab reading is the only way to actually know.

What this site is good for is the question before that one: how much radon potential does this county carry, how it ranks against the rest of the country, and what testing or mitigation actually costs if a test comes back high.

The question this site answers

"Is radon a problem where I live" doesn't have one national answer. EPA's Map of Radon Zones rates every US county on a 1993 geologic and radioactivity assessment, and RadonZoneCheck reports it county by county for 3144 counties covering 51 states and roughly 340,110,988 people, straight from EPA's own data.

A county average, not a house reading

1,065 US counties fall in EPA's highest-potential Zone 1, but a county rating is a predicted average across the whole county, never a reading for one specific house. EPA's own guidance is to test every home regardless of its county's zone; this site exists to explain what the zone means, not to replace an actual test.

Start with your county

Search or browse to your county to see its EPA radon zone, how it ranks nationally, and what testing and mitigation actually cost.