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Radon Levels in Sweetwater County, Wyoming

EPA puts Sweetwater County in Zone 1, its highest radon zone, and high results are common there: 49.6% of the 409 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

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  • Share at 4+ pCi/L

    49.6%

    5.3 pts above WY

    Sweetwater
    49.6%
    Wyoming
    44.3%

    409 tests, 2008 to 2017

  • Median result

    3.9pCi/L

    Below action level

    Sweetwater
    3.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    409

    6th of 22 by tests

    Sweetwater
    409
    Laramie
    1,834

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Wyoming

    10 of 22

    Middle half

    Sweetwater
    49.6%
    Sheridan
    69.5%

    By share, of 22 with 30+ tests

Read a result for Sweetwater County

Starts at Sweetwater County's median, 3.9 pCi/L

3.9pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.9 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Sweetwater County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Sweetwater County, At a glance

Sweetwater County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Sweetwater County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

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 Sweetwater County, 2008 to 2017, laboratory

Reported results by concentration band, Sweetwater County, 2008 to 2017, laboratory
Under 2 pCi/L: 22%2 to 4 pCi/L: 29%4 pCi/L and above: 49%

Of 409 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Sweetwater County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L8921.8%
2 to 4 pCi/L11728.6%
4 pCi/L and above20349.6%
What these figures count

These are the 409 tests reported to CDC for Sweetwater 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).

How to read these figures

Sweetwater County, Compared

Sweetwater County radon figures, compared

Calculated by Radon411

In Sweetwater County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (203 of 409) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 13.9 points higher. Across 23 Wyoming counties pooled together, 44.3% of tests reached that level, so Sweetwater County runs 5.3 points above its state.

Of 7 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 24.6% (Uinta County) to 68.3% (Lincoln County). By share, Sweetwater County is 10th of 22 Wyoming counties with 30 or more tests for the same period.

Half the tests came in under 3.9 pCi/L and half over it; the single highest reached 69.3 pCi/L. Below the action level, 89 tests (21.8%) came in under 2 pCi/L, against 25.5% statewide, and 117 tests (28.6%) fell between 2 and 4, against 30.2% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 49.6% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 20 tests taken after mitigation in Sweetwater County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Sweetwater County went from 433 tests (2005 to 2014) to 409 (2008 to 2017), the share going from 49.4% to 49.6%.

Sweetwater County against Wyoming, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Sweetwater County
Sweetwater County40949.6%3.9 pCi/LThis county
Wyoming, pooled23 counties, pooled7,63844.3%Not pooled−5.3 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−13.9 points
Sheridan Countyhighest in the state84669.5%5.8 pCi/L+19.9 points
Laramie Countylowest in the state1,83425.5%2.5 pCi/L−24.1 points
Lincoln County, WYborders it14268.3%7.8 pCi/L+18.7 points
Fremont County, WYborders it61855.7%4.7 pCi/L+6.1 points
Moffat County, COborders it21855.0%4.3 pCi/L+5.4 points
Sublette County, WYborders it6050.0%4.0 pCi/L+0.4 points
Carbon County, WYborders it8041.3%3.0 pCi/L−8.3 points
Summit County, UTborders it89433.1%2.6 pCi/L−16.5 points
Uinta County, WYborders it19924.6%2.2 pCi/L−25.0 points
Daggett County, UTborders it20.0%0.8 pCi/L−49.6 points
Where Sweetwater County's reported results fell, 2008 to 2017, laboratory, beside Wyoming and the United States
ResultSweetwater County testsSweetwater County shareWyoming shareU.S. shareAgainst Wyoming
Under 2 pCi/L8921.8%25.5%39.6%−3.7 points
2 to 4 pCi/L11728.6%30.2%24.7%−1.6 points
4 pCi/L and above20349.6%44.3%35.7%+5.3 points
Sweetwater County ranked among the 22 Wyoming counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Crook County5 of 225158.8%5.1 pCi/L
Hot Springs County6 of 225955.9%4.2 pCi/L
Natrona County7 of 221,05455.7%4.3 pCi/L
Fremont County8 of 2261855.7%4.7 pCi/L
Sublette County9 of 226050.0%4.0 pCi/L
Sweetwater County10 of 2240949.6%3.9 pCi/L
Teton County11 of 2227844.6%3.4 pCi/L
Campbell County12 of 2227143.9%3.5 pCi/L
Park County13 of 2250542.8%3.4 pCi/L
Big Horn County14 of 229942.4%3.5 pCi/L
Goshen County15 of 2216841.7%3.3 pCi/L
Sweetwater County ten-year laboratory totals, against Wyoming's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestWyoming, pooledChange from the row before
2008 to 201740949.6%3.9 pCi/L69.3 pCi/L44.3%−0.2 points
2007 to 201642249.8%3.9 pCi/L69.3 pCi/L44.6%+0.2 points
2006 to 201541749.6%3.9 pCi/L69.3 pCi/L45.3%+0.2 points
2005 to 201443349.4%3.9 pCi/L69.3 pCi/L45.5%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Sweetwater County, Geology

The ground under Sweetwater County

Predicted

Most of the ground under Sweetwater County is one class on USGS's geologic map: 99.6% of its land is high radon potential, with 0.4% moderate. All of it lies in the area the map calls Green River Basin, to which USGS gives a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Sweetwater County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Green River BasinCretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones.High1299.6%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Sweetwater County beside the ground around it

Sweetwater County has more high-potential ground than Wyoming as a whole: 99.6% of its land against 72.4%. Of the 8 counties that border it, none has as large a share of high-potential ground; Fremont County comes nearest at 92.7%.

Share of land by USGS radon potential: Sweetwater County, the 8 counties bordering it and Wyoming
AreaEPA zoneLow potentialModerate potentialHigh potential
Sweetwater CountyZone 1None0.4%99.6%
Daggett County, UTZone 2None93.7%6.3%
Moffat County, COZone 1None38.6%61.4%
Uinta CountyZone 1None13.9%86.1%
Sublette CountyZone 1None12.2%87.8%
Summit County, UTZone 2None43.6%56.4%
Lincoln CountyZone 1None62.5%37.5%
Fremont CountyZone 1None7.3%92.7%
Carbon CountyZone 1None29.2%70.8%
Wyoming23 counties, pooled by land areaVariesNone27.6%72.4%

The map rates the ground, not the air in any home.

Local help

Sweetwater County, Local resources

Radon testing and mitigation in Sweetwater County

What it means

Sweetwater County, Questions

Questions about radon in Sweetwater County

Are radon levels high in Sweetwater County?

Over the 2008 to 2017 laboratory totals, 49.6% of the radon tests reported to CDC for Sweetwater County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.9 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, 9 reported a higher share; pooled, the state comes to 44.3%.

Which counties border Sweetwater County?

Sweetwater County borders 8 counties: Daggett County, UT, Moffat County, CO, Uinta County, WY, Sublette County, WY, Summit County, UT, Lincoln County, WY, Fremont County, WY and Carbon County, WY.

Products

Sweetwater County, Products

Testing a home in Sweetwater County

In Sweetwater County, 49.6% of 409 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 Sweetwater 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

Sweetwater County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Sweetwater County

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Sweetwater County, Bordering counties

Counties bordering Sweetwater County

Calculated by Radon411

Sweetwater County, Cities and towns

Cities and towns in Sweetwater County

About 41,267 people live in Sweetwater County by the Census Bureau's estimate for July 1, 2025, 927 fewer than in 2020 (−2.2%). Spread over its land, that is 4.0 people to the square mile. Rock Springs alone is home to 22,936 of them, 55.6% of the total. Together its 6 incorporated places hold 84.6% of those residents; the other 15.4% live outside any of them. CDC's 409 reported tests for 2008 to 2017 work out to 9.9 per 1,000 residents (2025 estimate), close to Wyoming's 13.0.

From Rock Springs to Bairoil, CDC publishes no figure by town: each reads Sweetwater County's.

The cities and towns in Sweetwater County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Rock Springs22,936−2.4%55.6%
Green River11,450−3.1%27.7%
Wamsutter197−2.5%0.5%
Superior180−3.7%0.4%
Granger97+3.2%0.2%
Bairoil66−2.9%0.2%

6 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).

Sweetwater County, Homes

Homes in Sweetwater County

Of Sweetwater County's 19,226 homes, 60% are detached houses, against 68% across Wyoming; 20% are mobile homes. Half of its homes were built before 1980, close to Wyoming's 1980: 20% date from before 1960 and 21% from 2000 or later. 74% 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 in Sweetwater County, Wyoming, 2019 to 2023
HomesSweetwater CountyWyoming
Housing units19,226275,131
Detached houses60%68%
In buildings of 5 or more8%9%
Mobile homes20%12%
Built before 196020%24%
Built since 200021%24%
Middle year built19801980
Owner-occupied74%72%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.