Clackamas County, OR: EPA's radon zone, explained

Clackamas County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Nationally, Clackamas County ranks higher in radon potential than 31% of rated counties (the 31st percentile).

How Clackamas County compares

Clackamas County, Oregon is home to about 425,857 people across 1,870.712 square miles. That works out to roughly 228 people per square mile. By population, Clackamas County is the 64th largest of every county sharing its EPA zone — the 94th percentile by population within that zone. Geologically, Clackamas 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

A Zone 3 county like Clackamas County is predicted closer to the 0.4 pCi/L typical outdoors than to EPA's 4 pCi/L action level. A Zone 3 rating means Clackamas County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

Next steps for a home in Clackamas County

For a Clackamas County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Oregon's state radon program

For Clackamas County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Clackamas County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Clackamas County's figures come from

Clackamas County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.