What EPA's radon map says about Blaine County

EPA places Blaine County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Blaine County in the 73rd percentile nationally for radon potential — higher than 73% of the counties EPA has rated.

Blaine County by the numbers

About 6,903 people live in Blaine County, Montana, spread over 4,227.517 square miles. Population density there runs about 2 people per square mile. Among counties sharing Blaine County's EPA zone, it outranks 20% of them by population. EPA's geology-based Region 8 groups Blaine County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Blaine County

Blaine County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. That doesn't mean every Blaine 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 Blaine County

Mitigation cost doesn't depend on Blaine County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Montana's state radon program

Blaine County's test kit answers today; a Airthings radon monitor keeps answering for Blaine County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Blaine County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.