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Radon Levels in Grand County, Colorado

EPA puts Grand County in Zone 1, its highest radon zone. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

Predicted
Zone 1Highest predicted potential
Measured
44.1%of 136 tests reported to CDC (2023) were at or above 4 pCi/L
Your home
Test to knowNo area figure here is a reading of your home.
How to test this homeFind a certified tester

The data

Grand County, At a glance

Grand County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.

What EPA predicts hereScreening level, geology

EPA predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county as a whole.

USGS geologic potential: High across 98% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Grand County, 2023

Tests reported
136
At or above 4 pCi/L
44.1%
Median result
3.3 pCi/L
Reported results by concentration band, Grand County, 2023
Under 2 pCi/L: 29%2 to 4 pCi/L: 27%4 pCi/L and above: 44%

Of 136 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Grand County, 2023: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L4029.4%
2 to 4 pCi/L3626.5%
4 pCi/L and above6044.1%

CDC publishes this figure only for counties here, so there is no state or national number to compare Grand County, Colorado with.

What these figures count

Distribution of radon tests reported to CDC, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.

The figures at the top are for 2023: a percentage there is a share of radon tests reported to CDC for Grand County in 2023, and a percentage in a view below is a share of the tests reported for the year or period it names. It is not a share of homes in Grand County, and it is not a random sample: it counts only the tests people chose to run and that were reported.

CDC works out the shares and the median over pre-mitigation tests, counting a test not marked as before or after mitigation as one of them (136 for 2023). The median is the middle result of those tests, not of buildings. CDC also reports the number of buildings tested (126), a different count, so the two totals are not interchangeable.

Grand County's own published CDC figures beside those of the counties that border it, for the same period.

Each figure is that county’s own published CDC figure for 2023, counting radon tests reported to CDC, not homes. Grand County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. Every Colorado county’s own figure is in the Colorado county table.

Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

Grand County, State data

Colorado's own radon test data

Measured

What Colorado's own agencies publish about radon tests in Grand 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 Grand 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

43.8%

470 of 1,073 tests

Median result

3.3 pCi/L

Highest result

212.0 pCi/L

Tests behind these figures

1,073 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.

Radon Action Brief

National Radon Action MonthPre-sale

Grand County's radon brief, 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 the Grand County BriefSee a free sample

Area data, not a test of the building.

Local help

Grand County, Local resources

Radon testing and mitigation in Grand County

Who tests and fixes radon in Grand County: listed businesses, Colorado's radon program and test kits.

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

Grand County, Questions

Questions about radon in Grand County

Common questions

8 questions, answered from the figures above

Are radon levels high in Grand County?

In 2023, 44.1% of the radon tests reported to CDC for Grand County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.3 pCi/L. That is a share of reported tests, not of homes. EPA places Grand County in Zone 1, highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.

Radon levels: what a result meansWhat is radon?Radon levels in Colorado

How do I get a radon test in Grand County?

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. No radon testing business listed on Radon411 has an address in Grand County or names it as a service area yet. The Colorado radon program is the place to ask about certified testers and any test kit offer it runs.

Radon testing: how to test a homeRadon test kits comparedFree and low-cost kits by stateRadon Action Month checklistColorado radon program

Who does radon mitigation in Grand County?

No listed mitigator names Grand County as a service area yet; the Colorado directory lists 2 companies. 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. Your state radon program is the place to check whether Colorado requires one.

Radon mitigation: how it worksRadon mitigation costRadon mitigation systemsMitigators in Colorado

What EPA radon zone is Grand County in?

EPA places Grand County, Colorado in Zone 1, which EPA describes as highest predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.

Should I test my home in Grand County?

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.

When is the best time of year to test?

EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.

What does it cost to test?

EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.

Which counties border Grand County?

Grand County borders 8 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.

If you own, buy, sell or rent

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

The reported-test figures on this page describe Grand County, Colorado in 2023. They describe tests other people carried out in other buildings, and none of them measures yours.

Grand County in figures

The figures above, said in words

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

    • Predicted

      Predicted

      EPA places Grand County in Zone 1, highest predicted potential, as it does 52 other counties of Colorado's 64.

      Of the 8 bordering counties, EPA places Boulder County, Clear Creek County, Gilpin County, Jackson County, Larimer County and Summit County in Zone 1 and Eagle County and Routt County in Zone 2.

  • Reported tests

    Measured

    CDC has annual figures for Grand County for 10 years, 2014 to 2023. In 2023, 44.1% of 136 reported tests were at or above 4 pCi/L.

    Across those years the share ranged from 39.6% (2016) to 53.8% (2022). Few tests in a year can move it a long way.

  • Local record

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

    The county's largest incorporated places are Granby, Fraser and Kremmling; the figures here cover them as part of the county.

Products

Grand County, Products

Testing and mitigation products

Whatever the figures for Grand County 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.

Grand County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Grand County

Testing

5

Mitigation

3

Explore

Grand County, Bordering counties

Counties bordering Grand County

Calculated by Radon411
Why bordering counties matter

8 counties share a boundary with Grand County, computed from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county’s report can be worth reading alongside this one.

Grand County, Cities and towns

Cities and towns in Grand County

The radon figures on this page are for Grand County as a whole. They do not differ by city or town.

  • Granby
  • Fraser
  • Kremmling
  • Winter Park
  • Hot Sulphur Springs
  • Grand Lake

6 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files.

Grand County, 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.