Is Lake County, MT a radon risk area?

EPA places Lake 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. Rank it against the rest of the country and Lake County lands in the 86th percentile for radon potential.

Where Lake County sits nationally

About 33,403 people live in Lake County, Montana, spread over 1,490.505 square miles. That works out to roughly 22 people per square mile. Rank 440 by population within its EPA zone puts Lake County at the 59th percentile among zone peers. Geologically, Lake County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

What this actually means for a house in Lake County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Lake County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Lake County specifically.

If Lake County tests above the action level

Nothing about Lake County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Montana's state radon program

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

More on how this number was built

Lake 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.