Skip to content
RADON411

Locations and reports

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

Predicted
53 of 64counties in Zone 1, EPA's highest radon zone
Measured
By countyCDC publishes Colorado's test figures by county: 64 of 64 counties have one.
Your home
Test to knowNo area figure here is a reading of your home.
How to test this homeFind a certified tester

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 describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

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.

Colorado, Counties

Colorado counties by EPA zone

Predicted

Colorado's radon map, then all 64 counties by the zone EPA predicts for each, highest reported share of tests at or above 4 pCi/L first. Each has its own report.

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.Predicted potential for each county, not a reading of any home. Homes with elevated levels of radon have been found in all three zones.

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.

Radon Action Brief

National Radon Action MonthPre-sale

The radon brief for your Colorado county, in one dated file.

  • Your area's radon record, explained.
  • Your plan to test this week.
  • Fix costs and pros near you.

Save 64%Sale price: $8.99Price after the sale: $25Ends Jan 31Then $25

Get your Colorado county's BriefSee a free sample

Area data, not a test of the building.

What it means

Colorado, Questions

Questions about radon in Colorado

Common questions

9 questions, answered from the figures above

Is radon a problem in Colorado?

EPA's Map of Radon Zones places 53 of the 64 Colorado counties it classifies in Zone 1, the highest predicted potential, 11 in Zone 2 and 0 in Zone 3. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

Colorado on the radon mapRadon levels by state

Who does radon mitigation in Colorado?

Radon411's Colorado directory lists 2 radon businesses for testing, mitigation or both, each with the licensing list it was read from. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional.

How radon mitigation worksWhat mitigation costsRadon professionals in Colorado

How do I get a radon test in Colorado?

EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. The Colorado radon program is the place to ask about certified testers and any test kit offer it runs.

How to test a homeFree and low-cost kits by stateColorado radon program

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. Zone 1 is EPA's class for highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. A zone is a prediction for a county, not a measurement of any home.

Radon in Adams CountyRadon in Arapahoe CountyRadon in Baca County

Which Colorado counties have the highest radon?

64 of Colorado's 64 counties have an EPA radon zone published here. Radon411 will not rank counties on data it does not hold, and a zone is a prediction for an area rather than a measurement of any building.

What share of radon tests in Colorado are high?

CDC has published no statewide radon testing statistics for Colorado, so we cannot give a figure. Where CDC does publish one, the percentage describes radon tests reported to CDC, not homes.

Which EPA region is Colorado in?

Colorado is in EPA Region 8: Mountains and Plains.

Do I need to test my home in Colorado?

Yes, wherever you live in the state. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L.

Why does this page show coverage rather than one radon level for Colorado?

A statewide figure averages counties with very different geology and very different numbers of reported tests, so it hides more than it shows. The county report is the level at which the EPA zone, the geologic potential and the reported testing statistics are actually published, which is why the county table above links to every one of them.

If you own, buy, sell or rent

What these figures mean for each reader, with the guide that covers it

The zone counts on this page describe counties across Colorado. They are predictions for areas, and none of them measures your building.

Colorado in figures

The figures above, said in words

What the published data says about Colorado, in words. A zone and a share of tests describe an area, never the level in any one home.

    • Predicted

      Predicted

      EPA places 53 of Colorado's 64 counties in Zone 1 and 11 in Zone 2.

      Zone 1 counties, A to Z, begin with Adams County, Arapahoe County and Baca County; the county section below lists all 53.

    • Compared

      Calculated by Radon411

      83% of Colorado's counties with a zone on file are in Zone 1, a larger share than across all U.S. counties (34%). It is a share of counties, not of land, people or homes.

  • Reported tests

    Measured

    CDC has no statewide testing figure for Colorado on file here.

    64 of the 64 counties have a published county figure; the most tests in each one's latest year were reported for Jefferson County (3,068 tests in 2023), Denver County (2,277 tests in 2023) and Arapahoe County (1,990 tests in 2023).

  • Local record

    Colorado's radon program and its page are under Local resources.

    9 cities have a page setting the figures of the counties it lies in side by side: Colorado Springs, Grand Junction, Aurora, Longmont, Littleton, Lakewood, Arvada, Erie and Durango.

Products

Colorado, Products

Testing and mitigation products

Whatever the figures for Colorado show, only a test tells you about one home.

Test kits and monitors42

See all products

As an Amazon Associate, Radon411 earns from qualifying purchases.

Best radon monitors for Colorado homes, compared

Testing

5

Mitigation

3

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.

Colorado, Next steps

What to do next

  1. LearnKnow what radon isWhat radon is, how it gets indoors, and why a county zone is not a reading for your home.Learn about radon
  2. TestTest the building you live inShort-term or long-term, where the device goes, and closed-house conditions.How to test
  3. FixBring a high level downHow a mitigation system works, and the retest that confirms it.How mitigation works
  4. Find a proHire a certified professionalMeasurement and mitigation professionals by state, with their certifications.Find a professional

Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.