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 Sheridan County, Montana
EPA puts Sheridan County in Zone 1, its highest radon zone, and high results are common there: 75.7% of the 70 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
75.7%
30.2 pts above MT
- Sheridan
- 75.7%
- Montana
- 45.5%
70 tests, 2008 to 2017
Median result
6.5pCi/L
Action level reached
- Sheridan
- 6.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
70
13th of 23 by tests
- Sheridan
- 70
- 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
2 of 23
Top quarter
- Sheridan
- 75.7%
- Richland
- 78.6%
By share, of 23 with 30+ tests
Read a result for Sheridan County
Starts at Sheridan County's median, 6.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 6.5 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. Sheridan County's median reported result, 2008 to 2017.
The data
Sheridan County, At a glance
Sheridan County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Sheridan 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 Sheridan County, 2008 to 2017, laboratory
Under 2 pCi/L: 4%2 to 4 pCi/L: 20%4 pCi/L and above: 76%
Of 70 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 3 | 4.3% |
| 2 to 4 pCi/L | 14 | 20.0% |
| 4 pCi/L and above | 53 | 75.7% |
What these figures count
These are the 70 tests reported to CDC for Sheridan 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).
Sheridan County, Compared
Sheridan County radon figures, compared
Calculated by Radon411More than half: 75.7% of the 70 radon tests reported to CDC for Sheridan County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 2nd of 23 Montana counties with 30 or more tests for the same period. That is 30.2 points above the 45.5% pooled from 51 Montana counties.
The median result, 6.5 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 49.1 pCi/L. The rest split 4.3% under 2 pCi/L and 20.0% from 2 to 4 (Montana: 29.2% and 25.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 75.7% share point the same way here.
Williams County, ND, the one bordering county with a figure for the same period, reported 33.8%. 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 Sheridan County went from 70 tests (2005 to 2014) to 70 (2008 to 2017), the share going from 74.3% to 75.7%.
Nationally, every county with a figure for the same period pools to 35.7%; Sheridan County sits 40.0 points above it.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Sheridan County, Geology
The ground under Sheridan County
PredictedUSGS's geologic map puts all of Sheridan County's mapped land in one class: high radon potential. All of it lies in the area the map calls Great Plains (Glaciated), 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 |
|---|---|---|---|---|
| Great Plains (Glaciated) | Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium. | 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.
Sheridan County beside the ground around it
Sheridan County has more high-potential ground than Montana as a whole: 100% of its land against 78.5%. Of the 4 counties that border it, none has as large a share of high-potential ground; Daniels County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Sheridan County, Local resources
Radon testing and mitigation in Sheridan 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
Sheridan County, Questions
Questions about radon in Sheridan County
Are radon levels high in Sheridan County?
Over the 2008 to 2017 laboratory totals, 75.7% of the radon tests reported to CDC for Sheridan County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.5 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 1 reported a higher share; pooled, the state comes to 45.5%.
Which counties border Sheridan County?
Sheridan County borders 4 counties: Roosevelt County, MT, Daniels County, MT, Divide County, ND and Williams County, ND.
Products
Sheridan County, Products
Testing a home in Sheridan County
In Sheridan County, 75.7% of 70 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 Sheridan 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
MonitorAEGTEST
HOUND-1011 rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Sheridan County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Sheridan County
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Sheridan County, Bordering counties
Counties bordering Sheridan County
Calculated by Radon411- Radon levels in Roosevelt County, MTEPA zone 1
93.8%at or above 4 pCi/L
Median 8.7 pCi/L · 16 tests · 18.1 points above Sheridan County
- Radon levels in Divide County, NDEPA zone 1
50.0%at or above 4 pCi/L
Median 4.6 pCi/L · 14 tests · 25.7 points below Sheridan County
- Radon levels in Williams County, NDEPA zone 1
33.8%at or above 4 pCi/L
Median 2.9 pCi/L · 204 tests · 41.9 points below Sheridan County
- Radon levels in Daniels County, MTEPA zone 1
0.0%at or above 4 pCi/L
Median 2.5 pCi/L · 3 tests · 75.7 points below Sheridan County
Sheridan County, Cities and towns
Cities and towns in Sheridan County
About 3,436 people live in Sheridan County by the Census Bureau's estimate for July 1, 2025, 104 fewer than in 2020 (−2.9%). Spread over its land, that is 2.0 people to the square mile. Its largest town, Plentywood, has 1,619 residents, 47.1% of the total. Together its 4 incorporated places hold 61.3% of those residents; the other 38.7% live outside any of them. Testing is reported here more often than across the state: CDC's 70 reported tests for 2008 to 2017 come to 20.4 for every 1,000 residents (2025 estimate), against 8.6 for Montana.
From Plentywood to Outlook, CDC publishes no figure by town: each reads Sheridan County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Plentywood | 1,619 | −3.1% | 47.1% |
| Medicine Lake | 241 | −1.6% | 7.0% |
| Westby | 162 | −3.0% | 4.7% |
| Outlook | 83 | −3.5% | 2.4% |
4 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).
Sheridan County, Homes
Homes in Sheridan County
Sheridan County is a place of houses on their own lots: 78% of its 2,049 homes are detached single-family houses, against 69% across Montana. The homes are older than Montana's as a whole: half were built before 1962 (1980 for Montana), and 47% date from before 1960. Owners live in 77% of the occupied homes (Montana: 69%), so for most households a test and a fix are their own to order.
| Homes | Sheridan County | Montana |
|---|---|---|
| Housing units | 2,049 | 522,939 |
| Detached houses | 78% | 69% |
| In buildings of 5 or more | 5% | 9% |
| Mobile homes | 10% | 10% |
| Built before 1960 | 47% | 26% |
| Built since 2000 | 10% | 27% |
| Middle year built | 1962 | 1980 |
| Owner-occupied | 77% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.