Is Valley County, ID a radon risk area?

Valley County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Valley County in the 78th percentile nationally for radon potential — higher than 78% of the counties EPA has rated.

Valley County by the numbers

About 12,777 people live in Valley County, Idaho, spread over 3,665.12 square miles. Population density there runs about 3 people per square mile. Rank 704 by population within its EPA zone puts Valley County at the 34th percentile among zone peers. Valley County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Valley County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Valley County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Valley County tests above the action level

Nothing about Valley County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Idaho's state radon program

Valley County's test kit answers today; a Airthings radon monitor keeps answering for Valley County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Valley County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.