Skip to content
RADON411

Locations and reports

Radon Levels in Park County, Wyoming

EPA puts Park County in Zone 1, its highest radon zone, and high results are common there: 42.8% of the 505 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    42.8%

    1.5 pts below WY

    Park
    42.8%
    Wyoming
    44.3%

    505 tests, 2008 to 2017

  • Median result

    3.4pCi/L

    Below action level

    Park
    3.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    505

    5th of 22 by tests

    Park
    505
    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

    13 of 22

    Middle half

    Park
    42.8%
    Sheridan
    69.5%

    By share, of 22 with 30+ tests

Read a result for Park County

Starts at Park County's median, 3.4 pCi/L

3.4pCi/L

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

EPA’s reading of 3.4 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. Park County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Park County, At a glance

Park County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Park 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: Moderate across 52% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Park County, 2008 to 2017, laboratory

Reported results by concentration band, Park County, 2008 to 2017, laboratory
Under 2 pCi/L: 32%2 to 4 pCi/L: 25%4 pCi/L and above: 43%

Of 505 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Park County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L16031.7%
2 to 4 pCi/L12925.5%
4 pCi/L and above21642.8%
What these figures count

These are the 505 tests reported to CDC for Park 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

Park County, Compared

Park County radon figures, compared

Calculated by Radon411

In Park County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (216 of 505) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 7.1 points higher. Across 23 Wyoming counties pooled together, 44.3% of tests reached that level, so Park County runs 1.5 points below its state.

Of 8 neighbours with a figure, 5 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 38.5% (Washakie County) to 60.0% (Park County, MT). By share, Park County is 13th of 22 Wyoming counties with 30 or more tests for the same period.

Half the tests came in under 3.4 pCi/L and half over it; the single highest reached 177.3 pCi/L. Below the action level, 160 tests (31.7%) came in under 2 pCi/L, against 25.5% statewide, and 129 tests (25.5%) fell between 2 and 4, against 30.2% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 42.8% share point the same way here. USGS geology rates 52% of the county's land moderate radon potential. CDC also counts 37 tests taken after mitigation in Park County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Park County went from 374 tests (2005 to 2014) to 505 (2008 to 2017), the share going from 45.2% to 42.8%.

Park County against Wyoming, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Park County
Park County50542.8%3.4 pCi/LThis county
Wyoming, pooled23 counties, pooled7,63844.3%Not pooled+1.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−7.1 points
Sheridan Countyhighest in the state84669.5%5.8 pCi/L+26.7 points
Uinta Countylowest in the state19924.6%2.2 pCi/L−18.2 points
Park County, MTborders it15060.0%5.3 pCi/L+17.2 points
Hot Springs County, WYborders it5955.9%4.2 pCi/L+13.1 points
Fremont County, WYborders it61855.7%4.7 pCi/L+12.9 points
Carbon County, MTborders it4652.2%4.2 pCi/L+9.4 points
Teton County, WYborders it27844.6%3.4 pCi/L+1.8 points
Gallatin County, MTborders it1,60042.8%3.2 pCi/LLevel
Big Horn County, WYborders it9942.4%3.5 pCi/L−0.4 points
Washakie County, WYborders it13038.5%3.2 pCi/L−4.3 points
Where Park County's reported results fell, 2008 to 2017, laboratory, beside Wyoming and the United States
ResultPark County testsPark County shareWyoming shareU.S. shareAgainst Wyoming
Under 2 pCi/L16031.7%25.5%39.6%+6.2 points
2 to 4 pCi/L12925.5%30.2%24.7%−4.7 points
4 pCi/L and above21642.8%44.3%35.7%−1.5 points
Park 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
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
Carbon County16 of 228041.3%3.0 pCi/L
Washakie County17 of 2213038.5%3.2 pCi/L
Johnson County18 of 2213534.8%3.1 pCi/L
Park County ten-year laboratory totals, against Wyoming's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestWyoming, pooledChange from the row before
2008 to 201750542.8%3.4 pCi/L177.3 pCi/L44.3%−0.2 points
2007 to 201645143.0%3.4 pCi/L177.3 pCi/L44.6%−1.1 points
2006 to 201541344.1%3.4 pCi/L177.3 pCi/L45.3%−1.1 points
2005 to 201437445.2%3.6 pCi/L45.3 pCi/L45.5%First on file

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

Park County, Geology

The ground under Park County

Predicted

USGS's geologic map splits Park County: 51.9% of its land is moderate radon potential and 48.1% high. The map puts 51.8% of Park County in the area it calls Absaroka Volcanic Field and 34.1% in Big Horn Basin, with 2 smaller areas beside them. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).

USGS's geologic areas under Park County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Absaroka Volcanic FieldIntrusive and extrusive volcanic rocks and overlying sediments.Moderate1051.8%
Big Horn BasinCretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones.High1234.1%
Yellowstone Volcanic FieldBasalt and rhyolite flows and tuffs.High138.7%
Western Big Horn BasinCambrian to Miocene marine and continental sedimentary rocks including limestone, shale, sandstone, siltstone.High125.3%

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

Park County beside the ground around it

Wyoming as a whole has more high-potential ground than Park County: 72.4% of its land, against 48.1% here. Of the 8 counties that border it, 5 have more high-potential ground, Big Horn County the most at 100%.

Share of land by USGS radon potential: Park County, the 8 counties bordering it and Wyoming
AreaEPA zoneLow potentialModerate potentialHigh potential
Park CountyZone 1None51.9%48.1%
Hot Springs CountyZone 1None11.4%88.6%
Carbon County, MTZone 1None82.0%18.0%
Teton CountyZone 1None58.3%41.7%
Big Horn CountyZone 1NoneNone100%
Washakie CountyZone 1NoneNone100%
Fremont CountyZone 1None7.3%92.7%
Park County, MTZone 1None99.3%0.7%
Gallatin County, MTZone 1None21.0%79.0%
Wyoming23 counties, pooled by land areaVariesNone27.6%72.4%

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

Local help

Park County, Local resources

Radon testing and mitigation in Park County

What it means

Park County, Questions

Questions about radon in Park County

Are radon levels high in Park County?

Over the 2008 to 2017 laboratory totals, 42.8% of the radon tests reported to CDC for Park County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.4 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, 12 reported a higher share; pooled, the state comes to 44.3%.

Which counties border Park County?

Park County borders 8 counties: Hot Springs County, WY, Carbon County, MT, Teton County, WY, Big Horn County, WY, Washakie County, WY, Fremont County, WY, Park County, MT and Gallatin County, MT.

Products

Park County, Products

Testing a home in Park County

In Park County, 42.8% of 505 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 Park 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

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

Explore

Park County, Bordering counties

Counties bordering Park County

Calculated by Radon411

Park County, Cities and towns

Cities and towns in Park County

Park County is growing: the Census Bureau puts it at 31,171 residents on July 1, 2025, up 5.1% from 29,670 in 2020. Spread over its land, that is 4.5 people to the square mile. Its largest town, Cody, has 10,377 residents, 33.3% of the total. CDC's 505 reported tests for 2008 to 2017 work out to 16.2 per 1,000 residents (2025 estimate), close to Wyoming's 13.0.

From Cody to Frannie, CDC publishes no figure by town: each reads Park County's.

The cities and towns in Park County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Cody10,377+2.5%33.3%
Powell6,574+2.3%21.1%
Meeteetse315+0.6%1.0%
Frannieextends beyond Park County144+5.1%Counted whole

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). A place that extends beyond Park County is counted whole, so it has no share.

Park County, Homes

Homes in Park County

Park County is a place of houses on their own lots: 76% of its 14,813 homes are detached single-family houses, against 68% across Wyoming. Half of its homes were built before 1983, close to Wyoming's 1980: 21% date from before 1960 and 27% from 2000 or later. 75% 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 Park County, Wyoming, 2019 to 2023
HomesPark CountyWyoming
Housing units14,813275,131
Detached houses76%68%
In buildings of 5 or more4%9%
Mobile homes9%12%
Built before 196021%24%
Built since 200027%24%
Middle year built19831980
Owner-occupied75%72%

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