Is Broadwater County, MT a radon risk area?

EPA's own radon map rates Broadwater County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Broadwater County in the 74th percentile nationally for radon potential — higher than 74% of the counties EPA has rated.

Where Broadwater County sits nationally

About 8,302 people live in Broadwater County, Montana, spread over 1,192.359 square miles. That works out to roughly 7 people per square mile. Rank 815 by population within its EPA zone puts Broadwater County at the 23rd percentile among zone peers. Geologically, Broadwater County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Broadwater County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Broadwater 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 Broadwater County

Nothing about Broadwater County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Montana's state radon program

Broadwater County's test kit answers today; a Airthings radon monitor keeps answering for Broadwater County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

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