Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Fergus County, Montana
EPA puts Fergus County in Zone 1, its highest radon zone, and high results are common there: 72.4% of the 76 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
72.4%
26.9 pts above MT
- Fergus
- 72.4%
- Montana
- 45.5%
76 tests, 2008 to 2017
Median result
7.2pCi/L
Action level reached
- Fergus
- 7.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
76
11th of 23 by tests
- Fergus
- 76
- 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
3 of 23
Top quarter
- Fergus
- 72.4%
- Richland
- 78.6%
By share, of 23 with 30+ tests
Read a result for Fergus County
Starts at Fergus County's median, 7.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 7.2 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Fergus County's median reported result, 2008 to 2017.
The data
Fergus County, At a glance
Fergus County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Fergus County in
USGS geologic potential: High across 67% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Fergus County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 13%4 pCi/L and above: 72%
Of 76 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 11 | 14.5% |
| 2 to 4 pCi/L | 10 | 13.2% |
| 4 pCi/L and above | 55 | 72.4% |
What these figures count
These are the 76 tests reported to CDC for Fergus 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).
Fergus County, Compared
Fergus County radon figures, compared
Calculated by Radon411More than half: 72.4% of the 76 radon tests reported to CDC for Fergus County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 3rd of 23 Montana counties with 30 or more tests for the same period. That is 26.9 points above the 45.5% pooled from 51 Montana counties.
The median result, 7.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 119.1 pCi/L. The rest split 14.5% under 2 pCi/L and 13.2% from 2 to 4 (Montana: 29.2% and 25.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 72.4% share point the same way here.
Judith Basin County, the one bordering county with a figure for the same period, reported 64.3%. Statewide for the same period, Richland County reported the highest share (78.6%) and Cascade County the lowest (29.4%).
CDC's ten-year totals for Fergus County went from 61 tests (2005 to 2014) to 76 (2008 to 2017), the share going from 72.1% to 72.4%.
Nationally, every county with a figure for the same period pools to 35.7%; Fergus County sits 36.7 points above it. CDC also counts 10 tests taken after mitigation in Fergus County for the same period: tests in homes where a fix was already in.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Fergus County, Geology
The ground under Fergus County
PredictedUSGS's geologic map splits Fergus County: 66.9% of its land is high radon potential and 33.1% moderate. The map puts 42.6% of Fergus County in the area it calls Great Plains (Glaciated) and 33.1% in Plains and Mountains, with one smaller area beside them. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Great Plains (Glaciated) | Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium. | High | 13 | 42.6% |
| Plains and Mountains | Marine and continental shale, siltstone, and sandstone of Cretaceous and Tertiary ages, and volcanic rocks. | Moderate | 10 | 33.1% |
| Northern Rocky Mountains | Granitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium. | High | 13 | 24.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Fergus County beside the ground around it
Montana as a whole has more high-potential ground than Fergus County: 78.5% of its land, against 66.9% here. Of the 8 counties that border it, 3 have more high-potential ground, Blaine County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Fergus County, Local resources
Radon testing and mitigation in Fergus 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
Fergus County, Questions
Questions about radon in Fergus County
Are radon levels high in Fergus County?
Over the 2008 to 2017 laboratory totals, 72.4% of the radon tests reported to CDC for Fergus County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 7.2 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 45.5%.
Which counties border Fergus County?
Fergus County borders 8 counties: Judith Basin County, Petroleum County, Golden Valley County, Wheatland County, Chouteau County, Musselshell County, Blaine County and Phillips County.
Products
Fergus County, Products
Testing a home in Fergus County
In Fergus County, 72.4% of 76 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 Fergus 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
Monitor
Wave Radon battery smart radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- App only
Method: Alpha spectrometry
Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Fergus County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Fergus County
Explore
Fergus County, Bordering counties
Counties bordering Fergus County
Calculated by Radon411- Radon levels in Wheatland CountyEPA zone 2
100.0%at or above 4 pCi/L
Median 12.8 pCi/L · 1 test · 27.6 points above Fergus County
- Radon levels in Judith Basin CountyEPA zone 1
64.3%at or above 4 pCi/L
Median 5.9 pCi/L · 42 tests · 8.1 points below Fergus County
- Radon levels in Chouteau CountyEPA zone 1
54.5%at or above 4 pCi/L
Median 5.5 pCi/L · 11 tests · 17.9 points below Fergus County
- Radon levels in Musselshell CountyEPA zone 2
29.4%at or above 4 pCi/L
Median 2.6 pCi/L · 17 tests · 43.0 points below Fergus County
- Radon levels in Blaine CountyEPA zone 1
6.7%at or above 4 pCi/L
Median 1.2 pCi/L · 15 tests · 65.7 points below Fergus County
- Radon levels in Petroleum CountyEPA zone 2
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
- Radon levels in Golden Valley CountyEPA zone 2
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
- Radon levels in Phillips CountyEPA zone 1
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
Fergus County, Cities and towns
Cities and towns in Fergus County
The Census Bureau estimates 11,825 residents in Fergus County for July 1, 2025, 352 more than in 2020 (+3.1%). Spread over its land, that is 2.7 people to the square mile. Lewistown alone is home to 6,179 of them, 52.3% of the total. Together its 5 incorporated places hold 58.2% of those residents; the other 41.8% live outside any of them. CDC's 76 reported tests for 2008 to 2017 work out to 6.4 per 1,000 residents (2025 estimate), close to Montana's 8.6.
From Lewistown to Grass Range, CDC publishes no figure by town: each reads Fergus County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Lewistown | 6,179 | +3.5% | 52.3% |
| Denton | 207 | +2.0% | 1.8% |
| Moore | 203 | +4.1% | 1.7% |
| Winifred | 178 | +2.9% | 1.5% |
| Grass Range | 114 | +3.6% | 1.0% |
5 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).
Fergus County, Homes
Homes in Fergus County
Fergus County is a place of houses on their own lots: 75% of its 6,008 homes are detached single-family houses, against 69% across Montana. The homes are older than Montana's as a whole: half were built before 1967 (1980 for Montana), and 46% date from before 1960. 66% 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 | Fergus County | Montana |
|---|---|---|
| Housing units | 6,008 | 522,939 |
| Detached houses | 75% | 69% |
| In buildings of 5 or more | 9% | 9% |
| Mobile homes | 13% | 10% |
| Built before 1960 | 46% | 26% |
| Built since 2000 | 14% | 27% |
| Middle year built | 1967 | 1980 |
| Owner-occupied | 66% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.