Is Franklin County, ID a radon risk area?

EPA's own radon map rates Franklin County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. That puts Franklin County in the 43rd percentile nationally for radon potential — higher than 43% of the counties EPA has rated.

How Franklin County compares

About 15,638 people live in Franklin County, Idaho, spread over 663.019 square miles. That works out to roughly 24 people per square mile. Rank 704 by population within its EPA zone puts Franklin County at the 32nd percentile among zone peers. Geologically, Franklin County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Franklin County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. Middle-of-the-pack doesn't mean risk-free for any one Franklin County address — a moderate county average still leaves individual homes to test either side of it.

If Franklin County tests above the action level

Nothing about Franklin 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

Franklin County's test kit answers today; a Airthings radon monitor keeps answering for Franklin 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 Franklin County's numbers. Whatever zone Franklin County carries, the zone explainer covers what it does and doesn't tell you about any one house.