What EPA's radon map says about Asotin County

Asotin County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Nationally, Asotin County ranks higher in radon potential than 47% of rated counties (the 47th percentile).

Asotin County by the numbers

About 22,523 people live in Asotin County, Washington, spread over 636.075 square miles. That works out to roughly 35 people per square mile. Among counties sharing Asotin County's EPA zone, it outranks 43% of them by population. Geologically, Asotin County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

What this actually means for a house in Asotin County

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Asotin County's Zone 2 prediction lands in the gap between the two. Nothing about a Zone 2 label lowers the case for testing in Asotin County — EPA recommends it in every zone, moderate included.

If Asotin County tests above the action level

Mitigation cost doesn't depend on Asotin 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 Washington's state radon program

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