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 Hot Springs County, Wyoming
EPA puts Hot Springs County in Zone 1, its highest radon zone, and high results are common there: 55.9% of the 59 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
55.9%
11.6 pts above WY
- Hot Springs
- 55.9%
- Wyoming
- 44.3%
59 tests, 2008 to 2017
Median result
4.2pCi/L
Action level reached
- Hot Springs
- 4.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
59
20th of 22 by tests
- Hot Springs
- 59
- 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
6 of 22
Top quarter
- Hot Springs
- 55.9%
- Sheridan
- 69.5%
By share, of 22 with 30+ tests
Read a result for Hot Springs County
Starts at Hot Springs County's median, 4.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.2 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. Hot Springs County's median reported result, 2008 to 2017.
The data
Hot Springs County, At a glance
Hot Springs County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Hot Springs County in
USGS geologic potential: High across 89% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Hot Springs County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 29%4 pCi/L and above: 56%
Of 59 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 9 | 15.3% |
| 2 to 4 pCi/L | 17 | 28.8% |
| 4 pCi/L and above | 33 | 55.9% |
What these figures count
These are the 59 tests reported to CDC for Hot Springs 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).
Hot Springs County, Compared
Hot Springs County radon figures, compared
Calculated by Radon411More than half: 55.9% of the 59 radon tests reported to CDC for Hot Springs County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 6th of 22 Wyoming counties with 30 or more tests for the same period. That is 11.6 points above the 44.3% pooled from 23 Wyoming counties.
The median result, 4.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 172.5 pCi/L. The rest split 15.3% under 2 pCi/L and 28.8% from 2 to 4 (Wyoming: 25.5% and 30.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 55.9% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Fremont County at 55.7%, the lowest Washakie County at 38.5%. Statewide for the same period, Sheridan County reported the highest share (69.5%) and Uinta County the lowest (24.6%).
CDC's ten-year totals for Hot Springs County went from 67 tests (2005 to 2014) to 59 (2008 to 2017), the share going from 50.7% to 55.9%.
Nationally, every county with a figure for the same period pools to 35.7%; Hot Springs County sits 20.2 points above it.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Hot Springs County, Geology
The ground under Hot Springs County
PredictedMost of the ground under Hot Springs County is one class on USGS's geologic map: 88.6% of its land is high radon potential, with 11.4% moderate. The map puts 71.8% of Hot Springs County in the area it calls Big Horn Basin and 16.8% 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 |
|---|---|---|---|---|
| Big Horn Basin | Cretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones. | High | 12 | 71.8% |
| Big Horn Mountains | Precambrian granitic and metamorphic rocks locally overlain by marine clastic and carbonate sedimentary rocks. | High | 12 | 16.8% |
| Absaroka Volcanic Field | Intrusive and extrusive volcanic rocks and overlying sediments. | Moderate | 10 | 11.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Hot Springs County beside the ground around it
Hot Springs County has more high-potential ground than Wyoming as a whole: 88.6% of its land against 72.4%. Of the 3 counties that border it, 2 have more high-potential ground, Washakie County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Hot Springs County, Local resources
Radon testing and mitigation in Hot Springs 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
Hot Springs County, Questions
Questions about radon in Hot Springs County
Are radon levels high in Hot Springs County?
Over the 2008 to 2017 laboratory totals, 55.9% of the radon tests reported to CDC for Hot Springs County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.2 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 44.3%.
Which counties border Hot Springs County?
Hot Springs County borders 3 counties: Fremont County, Washakie County and Park County.
Products
Hot Springs County, Products
Testing a home in Hot Springs County
In Hot Springs County, 55.9% of 59 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 Hot Springs 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
MonitorX-Sense
XR0B-SR battery digital radon monitor with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Alpha spectrometry
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
Hot Springs County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Hot Springs County
Explore
Hot Springs County, Bordering counties
Counties bordering Hot Springs County
Calculated by Radon411- Radon levels in Fremont CountyEPA zone 1
55.7%at or above 4 pCi/L
Median 4.7 pCi/L · 618 tests · 0.2 points below Hot Springs County
- Radon levels in Park CountyEPA zone 1
42.8%at or above 4 pCi/L
Median 3.4 pCi/L · 505 tests · 13.1 points below Hot Springs County
- Radon levels in Washakie CountyEPA zone 1
38.5%at or above 4 pCi/L
Median 3.2 pCi/L · 130 tests · 17.4 points below Hot Springs County
Hot Springs County, Cities and towns
Cities and towns in Hot Springs County
Hot Springs County's population has barely moved since 2020: 4,600 residents on July 1, 2025 against 4,621 then, by the Census Bureau's estimates. Spread over its land, that is 2.3 people to the square mile. Thermopolis alone is home to 2,721 of them, 59.2% of the total. Together its 3 incorporated places hold 65.6% of those residents; the other 34.4% live outside any of them. CDC's 59 reported tests for 2008 to 2017 work out to 12.8 per 1,000 residents (2025 estimate), close to Wyoming's 13.0.
From Thermopolis to Kirby, CDC publishes no figure by town: each reads Hot Springs County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Thermopolis | 2,721 | −0.5% | 59.2% |
| East Thermopolis | 231 | +0.4% | 5.0% |
| Kirby | 67 | −1.5% | 1.5% |
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).
Hot Springs County, Homes
Homes in Hot Springs County
Of Hot Springs County's 2,490 homes, 73% are detached houses, against 68% across Wyoming; 20% are mobile homes. Half of its homes were built before 1973, close to Wyoming's 1980: 33% date from before 1960 and 11% from 2000 or later. 73% 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 | Hot Springs County | Wyoming |
|---|---|---|
| Housing units | 2,490 | 275,131 |
| Detached houses | 73% | 68% |
| In buildings of 5 or more | 2% | 9% |
| Mobile homes | 20% | 12% |
| Built before 1960 | 33% | 24% |
| Built since 2000 | 11% | 24% |
| Middle year built | 1973 | 1980 |
| Owner-occupied | 73% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.