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

EPA's own radon map rates Cascade County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally, Cascade County ranks higher in radon potential than 93% of rated counties (the 93rd percentile).

Where Cascade County sits nationally

Cascade County, Montana is home to about 84,523 people across 2,698.211 square miles. Averaged across its land area, Cascade County runs about 31 people per square mile. By population, Cascade County is the 219th largest of every county sharing its EPA zone — the 80th percentile by population within that zone. Cascade 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 Cascade County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Cascade 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 Cascade 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.

Testing and mitigation in Cascade County

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

Where Cascade 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. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.