Is Multnomah County, OR a radon risk area?

EPA's own radon map rates Multnomah County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. That puts Multnomah County in the 65th percentile nationally for radon potential — higher than 65% of the counties EPA has rated.

How Multnomah County compares

About 795,897 people live in Multnomah County, Oregon, spread over 431.012 square miles. That works out to roughly 1,847 people per square mile. Rank 27 by population within its EPA zone puts Multnomah County at the 97th percentile among zone peers. Multnomah County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Multnomah County's Zone 2 prediction lands in the gap between the two. A county-wide moderate average, like Multnomah County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Multnomah County

Nothing about Multnomah 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

Multnomah County's test kit answers today; a Airthings radon monitor keeps answering for Multnomah 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.