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Colorado Radon Map and Levels by County

Colorado's counties span EPA Zones 1 and 2. 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

    47.0%

    11.3 pts above U.S.

    Colorado
    47.0%
    U.S.
    35.7%

    96,367 tests across 63 counties, 2008 to 2017

  • Rank among states

    6 of 47

    Ten highest states

    Colorado
    47.0%
    North Dakota
    59.3%

    By share, every state pooled the same way, 2008 to 2017

  • Counties in EPA Zone 1

    53 of 64

    Most at highest potential

    Zone 1
    53
    Zone 2
    11

    Most counties sit in Zone 1; Zone 1 is the highest potential

  • Highest county

    71.4%

    Kit Carson County

    Kit Carson
    71.4%
    Alamosa
    26.6%

    Counties with 30+ tests, 2008 to 2017

Read a result for Colorado

Starts at EPA's action level

4.0pCi/L

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

EPA’s reading of 4.0 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. 47.0% of Colorado's reported tests reached 4 pCi/L, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Colorado, At a glance

Colorado at a glance

Predicted: EPA radon zone

64 of 64 counties classified

EPA classifies counties, not states. Of the 64 counties in Colorado with a zone, 53 are in Zone 1 and 11 in Zone 2.

  • Zone 1: Highest predicted potentialgreater than 4 pCi/L53 of 64 counties · 82.8%
  • Zone 2: Moderate predicted potential2 to 4 pCi/L11 of 64 counties · 17.2%

An EPA radon zone predicts a whole county. It is not intended to determine whether any individual home should be tested: homes with elevated levels occur in all three zones, and EPA recommends testing every home regardless of zone.

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

CDC test figures, county by county

CDC publishes Colorado's radon test figures by county: 64 of its 64 counties have one. Each one's share is in the county list.

How to read these figures

Colorado, Compared

Colorado radon figures, compared

Calculated by Radon411
Colorado, 2008 to 2017, laboratory
47.0%
of 96,367 tests at or above 4 pCi/L, pooled
Against the U.S.
+11.3points
35.7% pooled
Rank among the states
6 of 47
1 is the highest share
Counties with 30 or more tests
50
Highest
71.4%
Kit Carson County
Lowest
26.6%
Alamosa County

Pooled across 63 counties, 47.0% of the 96,367 radon tests reported to CDC for Colorado over the 2008 to 2017 laboratory totals were at or above 4 pCi/L: close to half or more. That is 6th of 47 states with county figures for the period; Ohio (52.3%) above it and Wisconsin (46.9%) below.

Its 50 counties with 30 or more tests run from 26.6% in Alamosa County to 71.4% in Kit Carson County; in 25 of them half or more of the reported tests reached 4 pCi/L. By band, 25 counties at 50% or more, 24 counties at 30% to 50%, 1 county at 15% to 30%.

The national pool for the same period is 35.7%, so Colorado runs 11.3 points above the country. EPA's 1993 map puts 53 of its 64 classified counties in Zone 1; the tests reported since bear that out at 47.0%.

Across its 4 overlapping ten-year totals, the share went from 49.5% (2005 to 2014) to 47.0% (2008 to 2017), down 2.5 points, with 2005 to 2014 the highest at 49.5%.

Colorado ranked among 47 states by pooled share of tests at or above 4 pCi/L, 2008 to 2017, laboratory
StateRankCountiesTestsAt or above 4 pCi/L
North Dakota1 of 47536,60759.3%
Nebraska2 of 479342,78258.5%
South Dakota3 of 47626,27558.5%
Iowa4 of 479995,24558.5%
Ohio5 of 478898,84052.3%
Colorado6 of 476396,36747.0%
Wisconsin7 of 477268,10446.9%
Montana8 of 47519,89345.5%
Wyoming9 of 47237,63844.3%
Kentucky10 of 4712028,79343.7%
Minnesota11 of 4787130,91243.4%
Colorado's highest and lowest counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/L
Kit Carson County1 of 504271.4%
Pueblo County2 of 503,52470.1%
Baca County3 of 503167.7%
Gilpin County4 of 5024064.6%
Washington County5 of 508662.8%
Las Animas County6 of 5018161.9%
Montrose County7 of 501,37060.7%
Chaffee County8 of 5052560.4%
Rio Blanco County9 of 503560.0%
Teller County10 of 501,12159.6%
Alamosa County50 of 507926.6%
Archuleta County49 of 5060031.2%
Prowers County48 of 5013731.4%
Mesa County47 of 502,63235.8%
Rio Grande County46 of 5021637.5%
Colorado's counties with 30 or more tests, by their own share at or above 4 pCi/L, 2008 to 2017, laboratory
ShareCountiesTheir testsFor example
50% or more2519,185Kit Carson County, Pueblo County, Baca County
30% to 50%2476,941Weld County, Routt County, Grand County
15% to 30%179Alamosa County
5% to 15%00None
Under 5%00None
Colorado ten-year laboratory totals, pooled, against the United States
PeriodCountiesTestsAt or above 4 pCi/LUnited StatesChange from the row before
2008 to 20176396,36747.0%35.7%−0.6 points
2007 to 20166389,53047.6%35.8%−1.1 points
2006 to 20156379,42848.8%36.3%−0.7 points
2005 to 20146368,56149.5%36.0%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period. CDC publishes no state or national figure.

Colorado, Counties

Colorado counties by EPA zone

Predicted

The map of Colorado, then its 64 counties zone by zone, each with its reported share at or above 4 pCi/L and a report of its own.

Colorado radon map by county: EPA radon zones. Map of Colorado's 64 counties shaded by EPA radon zone: Zone 1 in red-orange, Zone 2 in amber. 53 in Zone 1, 11 in Zone 2, 0 in Zone 3.
Colorado radon map by countyEPA radon zones for Colorado's counties: 53 counties in Zone 1, 11 counties in Zone 2, 0 counties in Zone 3.A prediction for each county, not a reading of any home; elevated homes occur in all three zones.

The 12 highest in Colorado, 2008 to 2017

Zone 1: highest predicted potential53

Local help

Colorado, Local resources

Local resources in Colorado

Who to ask in Colorado: its radon program, test kits and professionals.

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

Colorado, Questions

Questions about radon in Colorado

Is radon a problem in Colorado?

Colorado has 64 counties on EPA's Map of Radon Zones: Zone 1, the highest predicted potential, for 53; Zone 2 for 11; Zone 3 for 0. Pooled from 63 counties, 47.0% of the 96,367 radon tests reported to CDC over the 2008 to 2017 laboratory totals were at or above 4 pCi/L, 6th of 47 states.

Who does radon mitigation in Colorado?

Radon411's Colorado directory lists 25 radon businesses for testing, mitigation or both, each with the licensing list it was read from.

Which Colorado counties are in EPA radon Zone 1?

53 counties are in Zone 1: Adams County, Arapahoe County, Baca County, Bent County, Boulder County, Broomfield County, Chaffee County, Cheyenne County, and 45 more in the county table on this page.

Which Colorado counties have the highest radon?

By the share of reported tests at or above 4 pCi/L, 2008 to 2017, laboratory: Kit Carson County 71.4% (42 tests), Pueblo County 70.1% (3,524 tests), Baca County 67.7% (31 tests), Gilpin County 64.6% (240 tests), Washington County 62.8% (86 tests).

Which EPA region is Colorado in?

Colorado is in EPA Region 8: Mountains and Plains.

Products

Colorado, Products

Testing a home in Colorado

47.0% of the 96,367 tests reported to CDC for Colorado over the 2008 to 2017 laboratory totals reached 4 pCi/L: a short-term kit (2 to 90 days) gives a first answer in days, a long-term test the year-round average. A short-term kit (2 to 90 days) is the quick first check for a home in Colorado; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Colorado homes, compared

Explore

Cities in Colorado with their own page

Radon data is published by county, not by city. Each city page sets the figures of the counties the city lies in side by side.