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

EPA places Coos County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Coos County lands in the 24th percentile for radon potential.

Coos County by the numbers

Coos County, Oregon is home to about 64,326 people across 1,596.051 square miles. That works out to roughly 40 people per square mile. By population, Coos County is the 293rd largest of every county sharing its EPA zone — the 72nd percentile by population within that zone. Coos County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Coos County's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. Don't read Zone 3 as a pass for Coos County — EPA's guidance to test every home makes no exception for counties predicted low.

Testing and mitigation in Coos County

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

Where Coos County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Coos County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.