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, Wyoming
EPA puts Sheridan County in Zone 1, its highest radon zone, and high results are common there: 69.5% of the 846 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
69.5%
25.2 pts above WY
- Sheridan
- 69.5%
- Wyoming
- 44.3%
846 tests, 2008 to 2017
Median result
5.8pCi/L
Action level reached
- Sheridan
- 5.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
846
3rd of 22 by tests
- Sheridan
- 846
- Laramie
- 1,834
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 Wyoming
1 of 22
Top quarter
- Sheridan
- 69.5%
- Sheridan
- 69.5%
By share, of 22 with 30+ tests
Read a result for Sheridan County
Starts at Sheridan County's median, 5.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.8 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 98% 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: 10%2 to 4 pCi/L: 21%4 pCi/L and above: 69%
Of 846 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 84 | 9.9% |
| 2 to 4 pCi/L | 174 | 20.6% |
| 4 pCi/L and above | 588 | 69.5% |
What these figures count
These are the 846 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: 69.5% of the 846 radon tests reported to CDC for Sheridan County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 1st of 22 Wyoming counties with 30 or more tests for the same period. That is 25.2 points above the 44.3% pooled from 23 Wyoming counties.
The median result, 5.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 111.1 pCi/L. The rest split 9.9% under 2 pCi/L and 20.6% from 2 to 4 (Wyoming: 25.5% and 30.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 69.5% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Campbell County at 43.9%, the lowest Johnson County at 34.8%. Statewide for the same period, Lincoln County reported the highest share (68.3%) and Uinta County the lowest (24.6%).
CDC's ten-year totals for Sheridan County went from 969 tests (2005 to 2014) to 846 (2008 to 2017), the share going from 69.6% to 69.5%.
Nationally, every county with a figure for the same period pools to 35.7%; Sheridan County sits 33.8 points above it. CDC also counts 33 tests taken after mitigation in Sheridan 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.
Sheridan County, Geology
The ground under Sheridan County
PredictedMost of the ground under Sheridan County is one class on USGS's geologic map: 98.1% of its land is high radon potential, with 1.9% moderate. The map puts 65.3% of Sheridan County in the area it calls Powder River Basin and 32.8% in Big Horn Mountains, with one smaller area beside them. USGS gives both a radon index of 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Powder River Basin | Cretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones. | High | 12 | 65.3% |
| Big Horn Mountains | Precambrian granitic and metamorphic rocks locally overlain by marine clastic and carbonate sedimentary rocks. | High | 12 | 32.8% |
| Plains and Mountains | Marine and continental shale, siltstone, and sandstone of Cretaceous and Tertiary ages, and volcanic rocks. | Moderate | 10 | 1.9% |
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 Wyoming as a whole: 98.1% of its land against 72.4%. Of the 5 counties that border it, 1 has more high-potential ground, Big Horn County the most 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
- Wyoming Radon ProgramWyoming Radon Program, run by Wyoming Department of Health, answers questions about testing, mitigation and the rules in Wyoming.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Wyoming2 professionals are listed in Wyoming.
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, 69.5% of the radon tests reported to CDC for Sheridan County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.8 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 44.3%.
Which counties border Sheridan County?
Sheridan County borders 5 counties: Big Horn County, WY, Johnson County, WY, Big Horn County, MT, Campbell County, WY and Powder River County, MT.
Products
Sheridan County, Products
Testing a home in Sheridan County
In Sheridan County, 69.5% of 846 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 44.3% pooled across Wyoming. 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
Monitor
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
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
Sheridan County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Sheridan County
Explore
Sheridan County, Bordering counties
Counties bordering Sheridan County
Calculated by Radon411- Radon levels in Powder River County, MTEPA zone 1
62.5%at or above 4 pCi/L
Median 4.5 pCi/L · 8 tests · 7.0 points below Sheridan County
- Radon levels in Campbell County, WYEPA zone 1
43.9%at or above 4 pCi/L
Median 3.5 pCi/L · 271 tests · 25.6 points below Sheridan County
- Radon levels in Big Horn County, WYEPA zone 1
42.4%at or above 4 pCi/L
Median 3.5 pCi/L · 99 tests · 27.1 points below Sheridan County
- Radon levels in Johnson County, WYEPA zone 1
34.8%at or above 4 pCi/L
Median 3.1 pCi/L · 135 tests · 34.7 points below Sheridan County
- Radon levels in Big Horn County, MTEPA zone 1
28.6%at or above 4 pCi/L
Median 2.0 pCi/L · 21 tests · 40.9 points below Sheridan County
Sheridan County, Cities and towns
Cities and towns in Sheridan County
Sheridan County is growing: the Census Bureau puts it at 33,241 residents on July 1, 2025, up 7.2% from 31,006 in 2020. That works out to 13 people per square mile of land. Sheridan alone is home to 20,015 of them, 60.2% of the total. Together its 4 incorporated places hold 66.6% of those residents; the other 33.4% live outside any of them. Testing is reported here more often than across the state: CDC's 846 reported tests for 2008 to 2017 come to 25.5 for every 1,000 residents (2025 estimate), against 13.0 for Wyoming.
From Sheridan to Clearmont, CDC publishes no figure by town: each reads Sheridan County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Sheridan | 20,015 | +6.5% | 60.2% |
| Ranchester | 1,170 | +9.1% | 3.5% |
| Dayton | 825 | +1.1% | 2.5% |
| Clearmont | 123 | +6.0% | 0.4% |
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
Of Sheridan County's 15,236 homes, 73% are detached houses, against 68% across Wyoming; 8% are in buildings of five or more homes. Half of its homes were built before 1981, close to Wyoming's 1980: 27% date from before 1960 and 28% from 2000 or later. 70% of occupied homes are lived in by their owner (Wyoming: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Sheridan County | Wyoming |
|---|---|---|
| Housing units | 15,236 | 275,131 |
| Detached houses | 73% | 68% |
| In buildings of 5 or more | 8% | 9% |
| Mobile homes | 8% | 12% |
| Built before 1960 | 27% | 24% |
| Built since 2000 | 28% | 24% |
| Middle year built | 1981 | 1980 |
| Owner-occupied | 70% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.