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

Columbia 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. Rank it against the rest of the country and Columbia County lands in the 55th percentile for radon potential.

Where Columbia County sits nationally

Columbia County, Oregon is home to about 54,063 people across 658.686 square miles. Population density there runs about 82 people per square mile. By population, Columbia County is the 332nd largest of every county sharing its EPA zone — the 68th percentile by population within that zone. Geologically, Columbia 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 Columbia County

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Columbia County's Zone 2 prediction lands in the gap between the two. Columbia County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

Testing and mitigation in Columbia County

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

Where Columbia County's figures come from

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.