Is Gilliam County, OR a radon risk area?

Gilliam 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. That puts Gilliam County in the 34th percentile nationally for radon potential — higher than 34% of the counties EPA has rated.

How Gilliam County compares

About 1,971 people live in Gilliam County, Oregon, spread over 1,204.721 square miles. That works out to roughly 2 people per square mile. Rank 1003 by population within its EPA zone puts Gilliam County at the 3rd percentile among zone peers. Gilliam County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Gilliam County

Gilliam 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. Gilliam 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 Gilliam County

Nothing about Gilliam 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 Oregon's state radon program

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

More on how this number was built

Gilliam County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.