What EPA's radon map says about Twin Falls County

EPA's own radon map rates Twin Falls County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Twin Falls County sits at the 59th percentile nationally for radon potential — above 59 of every 100 rated counties.

How Twin Falls County compares

About 96,509 people live in Twin Falls County, Idaho, spread over 1,921.716 square miles. That works out to roughly 50 people per square mile. Among counties sharing Twin Falls County's EPA zone, it outranks 80% of them by population. Geologically, Twin Falls 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

Twin Falls County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). Twin Falls County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Next steps for a home in Twin Falls County

Mitigation cost doesn't depend on Twin Falls County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Idaho's state radon program

Twin Falls County's test kit answers today; a Airthings radon monitor keeps answering for Twin Falls 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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.