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Radon Levels in Park County, Colorado

EPA puts Park County in Zone 1, its highest radon zone, and high results are common there: 57.5% of the 106 radon tests reported to CDC (2023) 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

    57.5%

    18.6 pts above CO

    Park
    57.5%
    Colorado
    38.9%

    106 tests, 2023

  • Median result

    4.6pCi/L

    Action level reached

    Park
    4.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    106

    28th of 38 by tests

    Park
    106
    Jefferson
    3,068

    Reported to CDC before any fix, 2023

  • 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 Colorado

    1 of 38

    Top quarter

    Park
    57.5%
    Park
    57.5%

    By share, of 38 with 30+ tests

Read a result for Park County

Starts at Park County's median, 4.6 pCi/L

4.6pCi/L

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

EPA’s reading of 4.6 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, 2023.

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: High across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Park County, 2023

Share of reported tests at or above 4 pCi/L, by year, Park County
Share of reported tests at or above 4 pCi/L, by year, Park County
YearShare of reported tests at or above 4 pCi/L
201458.3%
201550.0%
201641.4%
201742.9%
201834.7%
201943.7%
202048.4%
202163.2%
202257.8%
202357.5%

2023: 57.5%. Across these years the share ran from 34.7% to 63.2%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 106 tests reported to CDC for Park County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Park County, Compared

Park County radon figures, compared

Calculated by Radon411

More than half: 57.5% of the 106 radon tests reported to CDC for Park County in 2023 read at least 4 pCi/L. That places it 1st of 38 Colorado counties with 30 or more tests for the same period. That is 18.6 points above the 38.9% pooled from 61 Colorado counties.

The median result, 4.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 121.1 pCi/L. The rest split 23.6% under 2 pCi/L and 18.9% from 2 to 4 (Colorado: 39.2% and 22.0%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 57.5% share point the same way here.

No bordering county with a figure for the same period reported a higher share; the closest is Teller County at 56.8%, the lowest Douglas County at 35.8%. Statewide for the same period, Teller County reported the highest share (56.8%) and Bent County the lowest (3.7%).

The busiest year on file was 2018, with 242 tests reported; the quietest, 2014, had 36.

Over 10 years of annual figures the share held within 2 points, from 58.3% in 2014 to 57.5% in 2023; its peak was 63.2% in 2021. Nationally, every county with a figure for the same period pools to 33.4%; Park County sits 24.1 points above it. CDC also counts 19 tests taken after mitigation in Park County for the same period: tests in homes where a fix was already in.

Share of reported tests at or above 4 pCi/L by year, Park County against Colorado2014 to 2023, years with 30 or more tests: Park County 58.3% to 57.5%, the state's pooled share 38.9% in 2023.
Park CountyColorado, pooled
Share of reported tests at or above 4 pCi/L by year, Park County against Colorado: data table
YearTestsPark County, at or above 4 pCi/LColorado, pooled
20143658.3%46.5%
20156250.0%47.2%
20165841.4%38.5%
20176342.9%41.0%
201824234.7%44.2%
201912643.7%44.1%
20209148.4%41.9%
202110663.2%47.3%
20228357.8%38.6%
202310657.5%38.9%
Park County against Colorado, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Park County
Park County10657.5%4.6 pCi/LThis county
Colorado, pooled61 counties, pooled21,80238.9%Not pooled−18.6 points
United States, pooled642 counties, pooled128,74033.4%Not pooled−24.1 points
Delta Countyhighest in the state12455.6%4.6 pCi/L−1.9 points
Bent Countylowest in the state1083.7%0.1 pCi/L−53.8 points
Teller County, COborders it16256.8%4.9 pCi/L−0.7 points
Chaffee County, COborders it16555.2%4.5 pCi/L−2.3 points
Lake County, COborders it3554.3%4.7 pCi/L−3.2 points
Fremont County, COborders it6650.0%4.0 pCi/L−7.5 points
Jefferson County, COborders it3,06841.8%3.2 pCi/L−15.7 points
Clear Creek County, COborders it5141.2%3.0 pCi/L−16.3 points
Summit County, COborders it29538.3%2.0 pCi/L−19.2 points
Douglas County, COborders it1,63535.8%2.4 pCi/L−21.7 points
Where Park County's reported results fell, 2023, beside Colorado and the United States
ResultPark County testsPark County shareColorado shareU.S. shareAgainst Colorado
Under 2 pCi/L2523.6%39.2%41.4%−15.6 points
2 to 4 pCi/L2018.9%22.0%25.2%−3.1 points
4 pCi/L and above6157.5%38.9%33.4%+18.6 points
Park County ranked among the 38 Colorado counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Park County1 of 3810657.5%4.6 pCi/L
Teller County2 of 3816256.8%4.9 pCi/L
Delta County3 of 3812455.6%4.6 pCi/L
Montrose County4 of 3821555.3%4.5 pCi/L
Chaffee County5 of 3816555.2%4.5 pCi/L
Lake County6 of 383554.3%4.7 pCi/L
Fremont County7 of 386650.0%4.0 pCi/L
Morgan County7 of 383850.0%4.0 pCi/L
Larimer County9 of 381,90249.4%3.8 pCi/L
Weld County10 of 3866346.0%3.5 pCi/L
Eagle County11 of 3831245.8%3.5 pCi/L
Park County radon tests by year, against Colorado's pooled share
YearTestsAt or above 4 pCi/LMedianHighestColorado, pooledChange from the row before
202310657.5%4.6 pCi/L121.1 pCi/L38.9%−0.3 points
20228357.8%5.8 pCi/L106.4 pCi/L38.6%−5.4 points
202110663.2%5.8 pCi/L238.0 pCi/L47.3%+14.8 points
20209148.4%3.9 pCi/L92.0 pCi/L41.9%+4.7 points
201912643.7%3.3 pCi/L76.1 pCi/L44.1%+9.0 points
201824234.7%2.4 pCi/L97.9 pCi/L44.2%−8.2 points
20176342.9%3.4 pCi/L230.9 pCi/L41.0%+1.5 points
20165841.4%3.3 pCi/L65.3 pCi/L38.5%−8.6 points
20156250.0%3.9 pCi/L117.9 pCi/L47.2%−8.3 points
20143658.3%4.7 pCi/L55.9 pCi/L46.5%First on file

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

Park County, State data

Colorado's own radon test data

Measured

What Colorado's own agencies publish about radon tests in Park County, with their period. These are not CDC's figures and are never added to them.

MeasuredState figures, not CDC's

What Colorado CDPHE reports for Park County

Radon data (county results): radon test results received from radon testing labs, primarily short-term household tests taken by the homeowner. Period: 2005-2025.

Share over 4 pCi/L

49.0%

521 of 1,064 tests

Median result

3.8 pCi/L

Highest result

338.1 pCi/L

Tests behind these figures

1,064 tests

  • CDPHE says these data do not give actual radon levels in homes that have not been tested.
  • When possible, only tests conducted before a mitigation system was installed are used.
  • Some counties have very small numbers of test results, and their summaries may be less representative.
  • These figures describe tests reported to Colorado CDPHE in this area. They count a different set of tests than CDC's figures and are not a reading of any one home.

Measured: Colorado CDPHE data, 2005-2025.

Park County, Geology

The ground under Park County

Predicted

Most of the ground under Park County is one class on USGS's geologic map: 99.7% of its land is high radon potential, with 0.3% moderate. All of it lies in the area the map calls Rocky Mountains, to which USGS gives a radon index of 15, in the high band (12 to 17).

USGS's geologic areas under Park County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Rocky MountainsPrecambrian granites, gneiss, amphibolite, variable uranium content, abundant shear zones.Sedimentary rocks shed from the granitic highlands.High1599.7%

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

Park County has more high-potential ground than Colorado as a whole: 99.7% of its land against 74.8%. Of the 8 counties that border it, 6 have more high-potential ground, Clear Creek County the most at 100%.

Share of land by USGS radon potential: Park County, the 8 counties bordering it and Colorado
AreaEPA zoneLow potentialModerate potentialHigh potential
Park CountyZone 1None0.3%99.7%
Lake CountyZone 1None29.1%70.9%
Teller CountyZone 1NoneNone100%
Chaffee CountyZone 1NoneNone100%
Summit CountyZone 1None4.7%95.3%
Jefferson CountyZone 1NoneNone100%
Clear Creek CountyZone 1NoneNone100%
Douglas CountyZone 1NoneNone100%
Fremont CountyZone 1NoneNone100%
Colorado64 counties, pooled by land areaVariesNone25.2%74.8%

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 Colorado's program says
Licensing of radon professionals
Listed contractors are certified by the National Radon Proficiency Program or the National Radon Safety Board, and must be licensed by the Colorado Department of Regulatory Agencies.
Disclosure when a home is sold or rented
As of August 7, 2023, landlords in Colorado are required to disclose radon information when a tenant signs a lease agreement.

What it means

Park County, Questions

Questions about radon in Park County

Are radon levels high in Park County?

In 2023, 57.5% of the radon tests reported to CDC for Park County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.6 pCi/L. Of 38 Colorado counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 38.9%.

Which counties border Park County?

Park County borders 8 counties: Lake County, Teller County, Chaffee County, Summit County, Jefferson County, Clear Creek County, Douglas County and Fremont County.

Products

Park County, Products

Testing a home in Park County

In Park County, 57.5% of 106 tests reported to CDC in 2023 reached 4 pCi/L, against 38.9% pooled across Colorado. 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 18,314 residents on July 1, 2025, up 5.1% from 17,425 in 2020. Spread over its land, that is 8.3 people to the square mile. No town dominates: Fairplay, the largest, has 743 residents, 4.1% of the total. Together its 2 incorporated places hold 5.8% of those residents; the other 94.2% live outside any of them. Testing is reported here more often than across the state: CDC's 106 reported tests for 2023 come to 5.8 for every 1,000 residents (2025 estimate), against 3.6 for Colorado.

From Fairplay to Alma, 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
Fairplay743+1.5%4.1%
Alma312+5.4%1.7%

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: 93% of its 14,362 homes are detached single-family houses, against 62% across Colorado. Half of its homes were built before 1989, close to Colorado's 1987: 7% date from before 1960 and 28% from 2000 or later. Owners live in 87% of the occupied homes (Colorado: 66%), so for most households a test and a fix are their own to order.

Homes in Park County, Colorado, 2019 to 2023
HomesPark CountyColorado
Housing units14,3622,545,124
Detached houses93%62%
In buildings of 5 or more2%22%
Mobile homes4%4%
Built before 19607%16%
Built since 200028%31%
Middle year built19891987
Owner-occupied87%66%

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