What EPA's radon map says about Cowlitz County

Cowlitz County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts Cowlitz County in the 26th percentile nationally for radon potential — higher than 26% of the counties EPA has rated.

Where Cowlitz County sits nationally

About 113,982 people live in Cowlitz County, Washington, spread over 1,141.176 square miles. Averaged across its land area, Cowlitz County runs about 100 people per square mile. Among counties sharing Cowlitz County's EPA zone, it outranks 80% of them by population. Geologically, Cowlitz 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 Cowlitz County

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Cowlitz County's Zone 3 prediction is the low end of the scale. Even at Zone 3, Cowlitz County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

If Cowlitz County tests above the action level

Mitigation cost doesn't depend on Cowlitz 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

Cowlitz County's test kit answers today; a Airthings radon monitor keeps answering for Cowlitz 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.