Dawson County, MT: EPA's radon zone, explained

Dawson County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Dawson County in the 74th percentile nationally for radon potential — higher than 74% of the counties EPA has rated.

Dawson County by the numbers

Dawson County, Montana is home to about 8,731 people across 2,371.926 square miles. Population density there runs about 4 people per square mile. By population, Dawson County is the 804th largest of every county sharing its EPA zone — the 25th percentile by population within that zone. Geologically, Dawson County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Dawson County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. That doesn't mean every Dawson County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Dawson County

For a Dawson 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 Montana's state radon program

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

Where Dawson 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.