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Radon in Longmont, Colorado

Longmont, Colorado spans 2 counties, Boulder County and Weld County. Radon data is published by county, so this page sets their figures side by side.

ColoradoAbout 100,109 people

What this means for you

  • Your area: Longmont lies in 2 counties. EPA rates Boulder County Zone 1 and Weld County Zone 1, where Zone 1 is the highest of its three radon zones. Zones are predictions for whole counties, and homes with elevated levels occur in all three zones.
  • Local tests: For 2023, the share of radon tests reported to CDC that were at or above 4 pCi/L was 34.2% in Boulder County (1,963 tests) and 46.0% in Weld County (663 tests). EPA's action level is 4 pCi/L.
  • Your home: The only way to know your home’s level is to test it.
How to testFind a certified tester

pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.

Longmont, What is published

What is published for Longmont

Information:

Radon data is published by county, not by city

Radon data is published by county, not by city. EPA assigns radon zones to counties, and CDC publishes radon test figures by county. Neither publishes a figure for Longmont, so every radon figure on this page belongs to a county and is labelled with it. Only a test tells you about one home.

Each county has its own CDC test figures, shown below side by side. About 100,109 people live in Longmont.

Longmont, Counties

Longmont's counties, side by side

Measured

Each county's own EPA zone and its own published CDC figures for 2023, the newest period any of them has. A county without a figure for that period is shown without one, never with a figure from another year.

  • Boulder County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    34.2%
    Median result
    2.5 pCi/L
    Tests reported
    1,963 tests
    Annual years on file
    10
  • Weld County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    46.0%
    Median result
    3.5 pCi/L
    Tests reported
    663 tests
    Annual years on file
    10
The counties Longmont lies in, each with its own EPA zone and its own published CDC figures for 2023
CountyEPA zoneReported tests at or above 4 pCi/LMedian reported resultTests reportedAnnual years on file
Boulder CountyZone 1: Highest predicted potential34.2%2.5 pCi/L1,963 tests10
Weld CountyZone 1: Highest predicted potential46.0%3.5 pCi/L663 tests10

The median reported pre-mitigation result for 2023 was 2.5 pCi/L in Boulder County and 3.5 pCi/L in Weld County.

CDC counts radon tests that were reported to it, not homes, and figures from few tests can swing widely from year to year. Each county’s report has its full history.

Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.

Longmont, Local resources

Local resources for Longmont

Who to ask in Colorado: the state's radon program, test kits and professionals.

Colorado's radon program

Colorado Department of Public Health and Environment

Colorado’s radon program answers questions about testing, mitigation and the rules where you live.

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.
Visit the program's page(opens in a new tab)

Test kits

The program says: Order a free radon test kit

Free and low-cost kitsCompare kits

Radon professionals

Radon testers and mitigators in Colorado, each with how its listing was checked.

Professionals in Colorado

Longmont, Questions

Questions about radon in Longmont

What radon zone is Longmont in?

EPA's Map of Radon Zones classifies counties, not cities. Boulder County and Weld County are in Zone 1 (highest predicted potential). A zone is a prediction for a whole county and never tells you the level in one home.

How many radon tests come back high in Longmont's counties?

For 2023, the share of radon tests reported to CDC that were at or above 4 pCi/L was 34.2% in Boulder County (1,963 tests) and 46.0% in Weld County (663 tests). Each is that county's own figure, counting tests reported to CDC, not homes. Radon411 does not average or combine them into a figure for the city.

Should I test my home in Longmont?

Yes. 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. How to test a home.

The answers use the published figures of Boulder County and Weld County, the counties Longmont lies in.

Longmont, Keep reading

Keep reading

Longmont / Next steps

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