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

EPA's own radon map rates Jefferson County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Jefferson County sits at the 48th percentile nationally for radon potential — above 48 of every 100 rated counties.

Where Jefferson County sits nationally

Jefferson County, Oregon is home to about 25,536 people across 1,781.696 square miles. Population density there runs about 14 people per square mile. By population, Jefferson County is the 548th largest of every county sharing its EPA zone — the 47th percentile by population within that zone. Jefferson 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 Jefferson County

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Jefferson County's Zone 2 prediction. A county-wide moderate average, like Jefferson County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Testing and mitigation in Jefferson County

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

Where Jefferson County's figures come from

Jefferson 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.