Montana Radon Map by County, EPA Zones & Basement Testing
Check the listed EPA radon zone pages across Montana. Start with a listed county if you want to know what a basement result means at 2.0 vs 4.0+ pCi/L before you price mitigation.
High Risk
Moderate
Low Risk
Official Evidence in Montana
1 of 1 listed counties have official evidence
Open a county page to see the official source context: measurement fields, local burden, state percentile, and the next step for no reading, 2.0-3.9, or 4.0+ pCi/L.
100%
covered
Measured
1
State source
0
CDC source
1
Needs source detail
0
Measured Risk Leaders in Montana
County rankings from actual reported radon tests
These lists rank the visible Montana county pages by measured radon signals, not by the EPA zone label alone. Use them to spot where the state hub has a real data story before opening individual county pages.
1
measured counties
State-level evidence read
This hub has measured high-burden counties, so the first click should be evidence-led.
The state hub is now doing a decision job: it separates first-click counties, retest counties, and lower-signal counties from 1 visible county measurement rows. 1 counties cross the high measured-burden band, so those pages should answer testing and 4.0+ action questions most directly.
First-click counties
Open Flathead County first when you need the strongest local answer. It is tagged Test-now from 37.8% 4.0+ - 7.3 pCi/L primary - 575 tests. 1 visible measured counties are elevated or high enough to review before lower-signal counties.
Buyer/seller lane
Buyer/seller lane: start with the elevated or high counties, require a fresh lowest-level test, and turn any 4.0+ property result into quote or credit math. The hub has 1 CDC-backed county rows to support that routing.
Retest lane
Retest lane: 2.0-3.9 pCi/L deserves more caution in the elevated/high county set than in lower-signal counties. The hub should send those users to county pages before product or cost paths.
Best county pages to open first
Start with these local evidence pages
Ranked by measured burden, 4.0+ share, test volume, and whether the EPA zone understates the measurement signal.
Highest 4.0+ share
Highest high-end reading
Most reported tests
Measured pattern
Among 1 visible counties with measurement tables, 1 land in the high measured-burden band and 1 land in high or elevated measured-burden bands. That lets this hub rank counties by observed test distribution instead of repeating the EPA map.
Map vs measurements
The strongest measured signals mostly align with the EPA zone structure, so the county pages can use the map as support while still leading with test data.
Source strategy
The measured rows shown here use CDC Tracking. This is still official evidence, but the hub should keep source caveats visible until a stable state table is available.
Already Tested
View Montana Cost Estimates
If you already have a radon result, skip the directory and move straight to local price guidance.
Understand the Number
2.0 vs 4.0 vs 8.0 pCi/L
Use the parent levels guide if you need the plain-English meaning of a radon result before browsing counties.
Need a Number First
Read the Testing Guide
Use the fastest valid radon test setup before you compare quotes or ask whether mitigation is worth it.
Browse Counties
Jump to the Directory
Open your county to see its EPA zone, testing meaning, and the point where mitigation becomes worth pricing.
Official State Resource
Montana radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure note
Montana does not have specific radon disclosure requirements. General property disclosure laws apply.
Credential note
Montana does not require state licensing for radon professionals.
Already tested? Get your itemized mitigation cost estimate.
View Montana Mitigation Cost Estimates ->