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Radon Levels in Park County, Montana

EPA puts Park County in Zone 1, its highest radon zone, and high results are common there: 60.0% of the 150 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

    60.0%

    14.5 pts above MT

    Park
    60.0%
    Montana
    45.5%

    150 tests, 2008 to 2017

  • Median result

    5.3pCi/L

    Action level reached

    Park
    5.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    150

    9th of 23 by tests

    Park
    150
    Missoula
    2,613

    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 Montana

    8 of 23

    Middle half

    Park
    60.0%
    Richland
    78.6%

    By share, of 23 with 30+ tests

Read a result for Park County

Starts at Park County's median, 5.3 pCi/L

5.3pCi/L

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

EPA’s reading of 5.3 pCi/L

At or above 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. 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 99% 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: 27%2 to 4 pCi/L: 13%4 pCi/L and above: 60%

Of 150 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/L4026.7%
2 to 4 pCi/L2013.3%
4 pCi/L and above9060.0%
What these figures count

These are the 150 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

More than half: 60.0% of the 150 radon tests reported to CDC for Park County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 8th of 23 Montana counties with 30 or more tests for the same period. That is 14.5 points above the 45.5% pooled from 51 Montana counties.

The median result, 5.3 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 56.7 pCi/L. The rest split 26.7% under 2 pCi/L and 13.3% from 2 to 4 (Montana: 29.2% and 25.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 60.0% share point the same way here.

No bordering county with a figure for the same period reported a higher share; the closest is Stillwater County at 55.9%, the lowest Gallatin County at 42.8%. 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 Park County went from 136 tests (2005 to 2014) to 150 (2008 to 2017), the share going from 58.1% to 60.0%.

Nationally, every county with a figure for the same period pools to 35.7%; Park County sits 24.3 points above it. CDC also counts 13 tests taken after mitigation in Park County for the same period: tests in homes where a fix was already in.

Park County against Montana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Park County
Park County15060.0%5.3 pCi/LThis county
Montana, pooled51 counties, pooled9,89345.5%Not pooled−14.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−24.3 points
Richland Countyhighest in the state4278.6%5.9 pCi/L+18.6 points
Cascade Countylowest in the state23529.4%1.7 pCi/L−30.6 points
Sweet Grass County, MTborders it988.9%11.9 pCi/L+28.9 points
Stillwater County, MTborders it5955.9%4.8 pCi/L−4.1 points
Carbon County, MTborders it4652.2%4.2 pCi/L−7.8 points
Park County, WYborders it50542.8%3.4 pCi/L−17.2 points
Gallatin County, MTborders it1,60042.8%3.2 pCi/L−17.2 points
Meagher County, MTborders it10.0%3.6 pCi/L−60.0 points
Where Park County's reported results fell, 2008 to 2017, laboratory, beside Montana and the United States
ResultPark County testsPark County shareMontana shareU.S. shareAgainst Montana
Under 2 pCi/L4026.7%29.2%39.6%−2.5 points
2 to 4 pCi/L2013.3%25.2%24.7%−11.9 points
4 pCi/L and above9060.0%45.5%35.7%+14.5 points
Park County ranked among the 23 Montana counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Fergus County3 of 237672.4%7.2 pCi/L
Jefferson County4 of 236271.0%6.3 pCi/L
Silver Bow County5 of 2317470.1%6.0 pCi/L
Judith Basin County6 of 234264.3%5.9 pCi/L
Lewis and Clark County7 of 2346861.8%5.1 pCi/L
Park County8 of 2315060.0%5.3 pCi/L
Beaverhead County9 of 233759.5%5.0 pCi/L
Mineral County10 of 233056.7%5.1 pCi/L
Stillwater County11 of 235955.9%4.8 pCi/L
Carbon County12 of 234652.2%4.2 pCi/L
Lincoln County13 of 237451.4%4.0 pCi/L
Park County ten-year laboratory totals, against Montana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMontana, pooledChange from the row before
2008 to 201715060.0%5.3 pCi/L56.7 pCi/L45.5%+0.3 points
2007 to 201614459.7%5.2 pCi/L56.7 pCi/L46.6%+1.8 points
2006 to 201514057.9%5.1 pCi/L56.7 pCi/L47.4%−0.2 points
2005 to 201413658.1%5.3 pCi/L56.7 pCi/L48.0%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

Most of the ground under Park County is one class on USGS's geologic map: 99.3% of its land is moderate radon potential, with 0.7% high. The map puts 64.2% of Park County in the area it calls Absaroka Volcanic Field and 35.1% in Plains and Mountains, with one smaller area beside them. USGS gives both a radon index of 10, in the moderate band (9 to 11).

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.Moderate1064.2%
Plains and MountainsMarine and continental shale, siltstone, and sandstone of Cretaceous and Tertiary ages, and volcanic rocks.Moderate1035.1%
Northern Rocky MountainsGranitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium.High130.7%

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

Montana as a whole has more high-potential ground than Park County: 78.5% of its land, against 0.7% here. Of the 6 counties that border it, 5 have more high-potential ground, Gallatin County the most at 79.0%.

Share of land by USGS radon potential: Park County, the 6 counties bordering it and Montana
AreaEPA zoneLow potentialModerate potentialHigh potential
Park CountyZone 1None99.3%0.7%
Sweet Grass CountyZone 2None99.2%0.8%
Gallatin CountyZone 1None21.0%79.0%
Stillwater CountyZone 1None100%None
Carbon CountyZone 1None82.0%18.0%
Meagher CountyZone 1None21.7%78.3%
Park County, WYZone 1None51.9%48.1%
Montana56 counties, pooled by land areaVariesNone21.5%78.5%

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 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

Park County, Questions

Questions about radon in Park County

Are radon levels high in Park County?

Over the 2008 to 2017 laboratory totals, 60.0% of the radon tests reported to CDC for Park County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.3 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 7 reported a higher share; pooled, the state comes to 45.5%.

Which counties border Park County?

Park County borders 6 counties: Sweet Grass County, MT, Gallatin County, MT, Stillwater County, MT, Carbon County, MT, Meagher County, MT and Park County, WY.

Products

Park County, Products

Testing a home in Park County

In Park County, 60.0% of 150 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 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 18,214 residents on July 1, 2025, up 5.7% from 17,229 in 2020. Spread over its land, that is 6.5 people to the square mile. Livingston alone is home to 9,290 of them, 51.0% of the total. Together its 2 incorporated places hold 52.9% of those residents; the other 47.1% live outside any of them. CDC's 150 reported tests for 2008 to 2017 work out to 8.2 per 1,000 residents (2025 estimate), close to Montana's 8.6.

From Livingston to Clyde Park, 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
Livingston9,290+7.5%51.0%
Clyde Park348+4.8%1.9%

2 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).

Park County, Homes

Homes in Park County

Park County is a place of houses on their own lots: 76% of its 9,597 homes are detached single-family houses, against 69% across Montana. Half of its homes were built before 1978, close to Montana's 1980: 34% date from before 1960 and 24% from 2000 or later. 70% of occupied homes are lived in by their owner (Montana: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Park County, Montana, 2019 to 2023
HomesPark CountyMontana
Housing units9,597522,939
Detached houses76%69%
In buildings of 5 or more7%9%
Mobile homes9%10%
Built before 196034%26%
Built since 200024%27%
Middle year built19781980
Owner-occupied70%69%

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