Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Lake County, Montana
EPA puts Lake County in Zone 1, its highest radon zone, and high results are common there: 40.3% of the 149 radon tests reported to CDC (2008 to 2017, laboratory totals) came back at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
40.3%
5.2 pts below MT
- Lake
- 40.3%
- Montana
- 45.5%
149 tests, 2008 to 2017
Median result
2.9pCi/L
Below action level
- Lake
- 2.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
149
10th of 23 by tests
- Lake
- 149
- Missoula
- 2,613
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Montana
21 of 23
Lowest quarter
- Lake
- 40.3%
- Richland
- 78.6%
By share, of 23 with 30+ tests
Read a result for Lake County
Starts at Lake County's median, 2.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.9 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Lake County's median reported result, 2008 to 2017.
The data
Lake County, At a glance
Lake County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Lake County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Lake County, 2008 to 2017, laboratory
Under 2 pCi/L: 38%2 to 4 pCi/L: 22%4 pCi/L and above: 40%
Of 149 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 56 | 37.6% |
| 2 to 4 pCi/L | 33 | 22.1% |
| 4 pCi/L and above | 60 | 40.3% |
What these figures count
These are the 149 tests reported to CDC for Lake County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Lake County, Compared
Lake County radon figures, compared
Calculated by Radon411In Lake County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (60 of 149) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 4.6 points higher. Across 51 Montana counties pooled together, 45.5% of tests reached that level, so Lake County runs 5.2 points below its state.
Of 3 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 37.8% (Flathead County) to 50.0% (Sanders County). By share, Lake County is 21st of 23 Montana counties with 30 or more tests for the same period.
Half the tests came in under 2.9 pCi/L and half over it; the single highest reached 107.3 pCi/L. Below the action level, 56 tests (37.6%) came in under 2 pCi/L, against 29.2% statewide, and 33 tests (22.1%) fell between 2 and 4, against 25.2% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 40.3% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 7 tests taken after mitigation in Lake County for the same period: tests in homes where a fix was already in.
CDC's ten-year totals for Lake County went from 124 tests (2005 to 2014) to 149 (2008 to 2017), the share going from 36.3% to 40.3%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Lake County, Geology
The ground under Lake County
PredictedUSGS's geologic map puts all of Lake County's mapped land in one class: high radon potential. All of it lies in the area the map calls Northern Rocky Mountains, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Northern Rocky Mountains | Granitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Lake County beside the ground around it
Lake County has more high-potential ground than Montana as a whole: 100% of its land against 78.5%. Of the 3 counties that border it, none has as large a share of high-potential ground; Flathead County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Lake County, Local resources
Radon testing and mitigation in Lake County
- Radon Control ProgramRadon Control Program, run by Montana DEQ, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Montana.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Energy Bureau staff manage the radon information toll-free hotline and distribute subsidized radon test kits to Montana residents.
- Compare kits
- See the Montana directoryNo professionals are listed in Montana yet. The state program can point you to registered testers and mitigators.
What Montana's program says
- Phone
- 1-800-546-0483
- Licensing of radon professionals
Montana DEQ does not certify or require proof of certification for the contractors listed.
What it means
Lake County, Questions
Questions about radon in Lake County
Are radon levels high in Lake County?
Over the 2008 to 2017 laboratory totals, 40.3% of the radon tests reported to CDC for Lake County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.9 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 20 reported a higher share; pooled, the state comes to 45.5%.
Which counties border Lake County?
Lake County borders 3 counties: Missoula County, Sanders County and Flathead County.
Products
Lake County, Products
Testing a home in Lake County
In Lake County, 40.3% of 149 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 45.5% pooled across Montana. In Zone 1 the year-round level in Lake County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorINKBIRD
INK-RD3 battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
First reading: Within 24 hours
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Lake County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Lake County
Explore
Lake County, Bordering counties
Counties bordering Lake County
Calculated by Radon411- Radon levels in Sanders CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 4.0 pCi/L · 38 tests · 9.7 points above Lake County
- Radon levels in Missoula CountyEPA zone 1
44.6%at or above 4 pCi/L
Median 3.4 pCi/L · 2,613 tests · 4.3 points above Lake County
- Radon levels in Flathead CountyEPA zone 1
37.8%at or above 4 pCi/L
Median 3.0 pCi/L · 891 tests · 2.5 points below Lake County
Lake County, Cities and towns
Cities and towns in Lake County
Lake County is growing: the Census Bureau puts it at 33,392 residents on July 1, 2025, up 6.9% from 31,245 in 2020. That works out to 22 people per square mile of land. No town dominates: Polson, the largest, has 5,653 residents, 16.9% of the total. Together its 3 incorporated places hold 26.0% of those residents; the other 74.0% live outside any of them. Reported testing is thin here: 149 tests over 2008 to 2017, or 4.5 for every 1,000 residents (2025 estimate), where Montana as a whole comes to 8.6.
From Polson to St. Ignatius, CDC publishes no figure by town: each reads Lake County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Polson | 5,653 | +9.2% | 16.9% |
| Ronan | 2,209 | +11.5% | 6.6% |
| St. Ignatius | 828 | +5.6% | 2.5% |
3 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Lake County, Homes
Homes in Lake County
Lake County is a place of houses on their own lots: 78% of its 16,457 homes are detached single-family houses, against 69% across Montana. Half of its homes were built before 1986, close to Montana's 1980: 18% date from before 1960 and 27% from 2000 or later. 74% of occupied homes are lived in by their owner (Montana: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Lake County | Montana |
|---|---|---|
| Housing units | 16,457 | 522,939 |
| Detached houses | 78% | 69% |
| In buildings of 5 or more | 4% | 9% |
| Mobile homes | 10% | 10% |
| Built before 1960 | 18% | 26% |
| Built since 2000 | 27% | 27% |
| Middle year built | 1986 | 1980 |
| Owner-occupied | 74% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.