What EPA's radon map says about Sweet Grass County

Sweet Grass County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Rank it against the rest of the country and Sweet Grass County lands in the 35th percentile for radon potential.

Sweet Grass County by the numbers

About 3,757 people live in Sweet Grass County, Montana, spread over 1,855.536 square miles. Population density there runs about 2 people per square mile. Among counties sharing Sweet Grass County's EPA zone, it outranks 6% of them by population. Sweet Grass County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Sweet Grass County

EPA's Zone 2 rating for Sweet Grass County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. A county-wide moderate average, like Sweet Grass County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Next steps for a home in Sweet Grass County

Mitigation cost doesn't depend on Sweet Grass 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

Sweet Grass County's test kit answers today; a Airthings radon monitor keeps answering for Sweet Grass 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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.