What EPA's radon map says about Pondera County

EPA's own radon map rates Pondera County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Pondera County sits at the 72nd percentile nationally for radon potential — above 72 of every 100 rated counties.

How Pondera County compares

About 6,078 people live in Pondera County, Montana, spread over 1,624.567 square miles. That works out to roughly 4 people per square mile. Among counties sharing Pondera County's EPA zone, it outranks 18% of them by population. Pondera County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Pondera County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. That doesn't mean every Pondera County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

If Pondera County tests above the action level

Mitigation cost doesn't depend on Pondera 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

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

Pondera County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Pondera County carries, the zone explainer covers what it does and doesn't tell you about any one house.