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

Sanders County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 78th percentile for radon potential — Sanders County outranks 78% of every county EPA has rated.

How Sanders County compares

Sanders County, Montana is home to about 13,895 people across 2,760.4 square miles. That works out to roughly 5 people per square mile. By population, Sanders County is the 689th largest of every county sharing its EPA zone — the 35th percentile by population within that zone. EPA's geology-based Region 8 groups Sanders County with 290 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Sanders County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Sanders County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Next steps for a home in Sanders County

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

Where Sanders 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.