Montana has 56 counties, with 49 classified as EPA Zone 1 (highest risk). With an average radon level of 8.63 pCi/L, Montana state testing data reveals significantly elevated risks across multiple counties. Testing is highly recommended.
Montana is the 4th most expansive state in terms of size and the 44th most populous. It also happens to be the 48th most densely populated in the entire US.
Montana does have an active radon program, dedicated to educating citizens about the risks associated with the deadly gas. You can find more information on Radon, testing and mitigation at the official page.
Explore radon data organized by metro region, including average levels, hotspot cities, and local mitigation professionals.
Cities with the most user-submitted radon test data, ranked by number of submissions.
| City | Avg User Radon Level | Submissions |
|---|---|---|
| Butte | 10.20 pCi/L | 10 |
| Missoula | 6.25 pCi/L | 8 |
| Florence | 11.67 pCi/L | 3 |
| Bozeman | 10.33 pCi/L | 3 |
| Helena | 8.67 pCi/L | 3 |
| Stevensville | 7.67 pCi/L | 3 |
| Sidney | 7.33 pCi/L | 3 |
| Billings | 5.33 pCi/L | 3 |
| Miles City | 3.33 pCi/L | 3 |
| Kalispell | 7.50 pCi/L | 2 |
| Great Falls | 4.50 pCi/L | 2 |
| Whitefish | 4.00 pCi/L | 2 |
| Ennis | 9.00 pCi/L | 1 |
| Livingston | No submissions | 0 |
All 56 Montana counties with their EPA radon zone classification and user-submitted average radon levels.
Browse radon data for individual cities across Montana. Each city page includes user-submitted radon levels, local contractors, and mitigation resources.