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

Park County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Park County ranks higher in radon potential than 81% of rated counties (the 81st percentile).

Park County by the numbers

Park County, Montana is home to about 18,074 people across 2,802.479 square miles. Population density there runs about 6 people per square mile. By population, Park County is the 600th largest of every county sharing its EPA zone — the 44th percentile by population within that zone. Geologically, Park County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

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

Next steps for a home in Park County

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

Where Park County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Park County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.