Locations and reports
Radon Levels in Custer County, Colorado
What this means for you
- Your area: EPA rates Custer County Zone 1, the highest of its three radon zones. That is a prediction for the whole county, and homes with elevated levels occur in all three zones.
- Local tests: Of 35 radon tests reported to CDC for Custer County (2023), 45.7% were at or above 4 pCi/L, EPA's action level.
- Your home: The only way to know your home’s level is to test it.
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.
In 2023, 45.7% of the radon tests reported to CDC for Custer County, Colorado came back at or above the EPA action level of 4 pCi/L, and the median result was 3.5 pCi/L. EPA's Map of Radon Zones places the county in Zone 1, highest predicted potential. Radon levels vary from home to home, so only a test measures the level in yours.
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county as a whole.
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.
USGS geologic potential: Low across 100% of the county's land area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Custer County, 2023
- Tests reported
- 35
- At or above 4 pCi/L
- 45.7%
- Median result
- 3.5 pCi/L
Of 35 pre-mitigation tests reported to CDC, not homes in this area. CDC publishes the share in each band, not a count per band, so the per-band counts in the table are calculated by Radon411 and rounded to add up to the published total.
| Result band | Tests Calculated by Radon411 | Share Measured |
|---|---|---|
| Under 2 pCi/L | 11 | 31.4% |
| 2 to 4 pCi/L | 8 | 22.9% |
| 4 pCi/L and above | 16 | 45.7% |
Distribution of tested buildings, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Custer County, In figures
Custer County in figures
What the published data says about Custer County, in words. A zone and a share of tests describe an area, never the level in any one home.
Predicted
PredictedEPA places Custer County in Zone 1, highest predicted potential, as it does 52 other counties of Colorado's 64.
Of the 4 bordering counties, EPA places Fremont County, Huerfano County and Pueblo County in Zone 1 and Saguache County in Zone 2.
Reported tests
MeasuredCDC has annual figures for Custer County for 10 years, 2014 to 2023. In 2023, 45.7% of 35 reported tests were at or above 4 pCi/L.
Across those years the share ranged from 34.6% (2020) to 58.6% (2017). 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 Silver Cliff and Westcliffe; the figures here cover them as part of the county.
Custer County, Reported testing
Reported testing over time
Measured| Year | Median reported result | Highest reported result | Share of tests at or above 4 pCi/L |
|---|---|---|---|
| 2014 | 4.6 pCi/L | 9.2 pCi/L | 57.1% |
| 2015 | 3.7 pCi/L | 8.5 pCi/L | 50.0% |
| 2016 | 3.5 pCi/L | 33.8 pCi/L | 50.0% |
| 2017 | 4.6 pCi/L | 37.4 pCi/L | 58.6% |
| 2018 | 3.3 pCi/L | 19.9 pCi/L | 47.5% |
| 2019 | 3.3 pCi/L | 201.1 pCi/L | 42.3% |
| 2020 | 1.9 pCi/L | 49.7 pCi/L | 34.6% |
| 2021 | 3.1 pCi/L | 64.9 pCi/L | 41.4% |
| 2022 | 1.9 pCi/L | 18.4 pCi/L | 34.8% |
| 2023 | 3.5 pCi/L | 217.6 pCi/L | 45.7% |
What these figures count
Every percentage here is a share of radon tests reported to CDC for Custer County in 2023. It is not a share of homes in Custer County, and it is not a random sample: it counts only the tests people chose to run and that were reported.
The shares and the median are calculated from pre-mitigation tests (35 for 2023). CDC also reports the number of buildings tested (32), a different count, so the two totals are not interchangeable.
Custer County, State data
Colorado's own radon test data
MeasuredWhat Colorado's own agencies publish about radon tests in Custer County, with their period. These are not CDC's figures and are never added to them.
What Colorado CDPHE reports for Custer 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
44.3%
194 of 438 tests
Median result
3.3 pCi/L
Highest result
217.6 pCi/L
Tests behind these figures
438 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.
Custer County, Comparison
How Custer County compares
MeasuredCuster County's own published CDC figures beside those of the counties that border it, for the same period.
Share of reported tests at or above 4 pCi/L
Measured2023, highest first. Each county’s own published CDC figure.
- Fremont CountyCO66 tests50.0%
- Custer CountyThis page35 tests45.7%
- Pueblo CountyCO342 tests44.4%
- Saguache CountyCO12 tests41.7%
- Huerfano CountyCO53 tests28.3%
Median reported result
Measured2023, highest first. Each county’s own published CDC figure.
- Fremont CountyCO66 tests4.0 pCi/L
- Custer CountyThis page35 tests3.5 pCi/L
- Pueblo CountyCO342 tests3.5 pCi/L
- Saguache CountyCO12 tests3.1 pCi/L
- Huerfano CountyCO53 tests1.3 pCi/L
Each figure is that county’s own published CDC figure for 2023, counting radon tests reported to CDC, not homes. Custer 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.
CDC publishes this figure only for counties here, so there is no state or national number to compare Custer County, Colorado with.
Custer County, Bordering counties
Counties bordering Custer County
Calculated by Radon4114 counties share a boundary with Custer 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.
Custer County, Local resources
Local resources in Colorado
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.
Test kits
The program says: Order a free radon test kit
Radon professionals
No professionals are listed in Colorado yet. The state program can point you to registered testers and mitigators.
See the Colorado directoryCuster County, Cities and towns
Cities and towns in Custer County
The radon figures on this page are for Custer County as a whole. They do not differ by city or town.
- Silver Cliff
- Westcliffe
2 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files.
Custer County, Questions
Questions about radon in Custer County
Common questions8 questions, answered from the figures above
Are radon levels high in Custer County?
In 2023, 45.7% of the radon tests reported to CDC for Custer County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. That is a share of reported tests, not of homes. EPA places Custer 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.
How do I get a radon test in Custer 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 certified tester listed on Radon411 names Custer County as a service area yet. The Colorado radon program is the place to ask about certified testers and any test kit offer it runs.
How to test a homeTest kits comparedFree and low-cost kits by stateColorado radon program
Who does radon mitigation in Custer County?
Radon411 has no certified mitigators listed for Colorado yet. 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.
How radon mitigation worksWhat mitigation costsColorado radon program
What EPA radon zone is Custer County in?
EPA places Custer 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 Custer 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 Custer County?
Custer County borders 4 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.
What these figures mean if you own, buy, sell or rent
The reported-test figures on this page describe Custer County, Colorado in 2023. They describe tests other people carried out in other buildings, and none of them measures yours.
- How to test a home
If you own your home
Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.
- Buying a house: radon guide
If you are buying
Ask for past results and any system's post-mitigation test, and test during the sale.
- Selling a house: radon guide
If you are selling
Testing before you list puts the timing in your hands; disclosure rules differ by state.
- Radon in rental homes
If you rent, or rent out a home
A tenant can test; a fix is the owner's to make, and duties differ by state.
How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.
Custer County, Products
Testing and mitigation products
Whatever the figures for Custer County show, only a test tells you about one home.
Testing
- Short-term test kitsPassive detectors exposed for a few days under closed-building conditions, then analyzed by a lab.
- Long-term test kitsDetectors exposed for more than 90 days, for a closer picture of the annual average.
- Continuous monitorsPowered devices that log radon on a repeating cycle, often used for transaction tests.
- Digital detectorsConsumer devices that display a running radon reading without a lab.
- Water radon testsKits for radon dissolved in well water, analyzed by a lab.
Mitigation
- Mitigation fansThe inline fan that keeps a soil depressurization system running, sized by the installer.
- System indicatorsU-tube manometers and fan alarms that show whether a mitigation system is still working.
- Sealing materialsCrack, joint and sump sealing used alongside a mitigation system, not instead of one.
Custer County / Next steps
What to do next
Learn
Know what radon is
What radon is, how it gets indoors, and why a county zone is not a reading for your home.
Learn about radonTest
Test the building you live in
Short-term or long-term, where the device goes, and closed-house conditions.
How to testFix
Bring a high level down
How a mitigation system works, and the retest that confirms it.
How mitigation worksFind a pro
Hire a certified professional
Measurement 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.