Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Summit County, Colorado
EPA puts Summit County in Zone 1, its highest radon zone, and 38.3% of its 295 reported radon tests (2023) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
38.3%
0.6 pts below CO
- Summit
- 38.3%
- Colorado
- 38.9%
295 tests, 2023
Median result
2.0pCi/L
Below action level
- Summit
- 2.0 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
295
14th of 38 by tests
- Summit
- 295
- Jefferson
- 3,068
Reported to CDC before any fix, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Colorado
22 of 38
Middle half
- Summit
- 38.3%
- Park
- 57.5%
By share, of 38 with 30+ tests
Read a result for Summit County
Starts at Summit County's median, 2.0 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.0 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Summit County's median reported result, 2023.
The data
Summit County, At a glance
Summit County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Summit County in
USGS geologic potential: High across 95% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Summit County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 64.7% |
| 2015 | 59.9% |
| 2016 | 52.1% |
| 2017 | 43.1% |
| 2018 | 42.0% |
| 2019 | 39.7% |
| 2020 | 41.9% |
| 2021 | 65.4% |
| 2022 | 45.5% |
| 2023 | 38.3% |
2023: 38.3%. Across these years the share ran from 38.3% to 65.4%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 295 tests reported to CDC for Summit County over 2023, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Summit County, Compared
Summit County radon figures, compared
Calculated by Radon411In Summit County, about 4 in 10 reported tests in 2023 (113 of 295) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 4.9 points higher. Across 61 Colorado counties pooled together, 38.9% of tests reached that level, so Summit County runs 0.6 points below its state.
Of 5 neighbours with a figure, all 5 reported a larger share at or above 4 pCi/L; the spread is 41.2% (Clear Creek County) to 57.5% (Park County). By share, Summit County is 22nd of 38 Colorado counties with 30 or more tests for the same period.
Year by year, 2014 opened at 64.7% and 2023 closed at 38.3% (down 26.4 points), with 2021 the high at 65.4%. Half the tests came in under 2.0 pCi/L and half over it; the single highest reached 73.9 pCi/L. Below the action level, 145 tests (49.2%) came in under 2 pCi/L, against 39.2% statewide, and 37 tests (12.5%) fell between 2 and 4, against 22.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 38.3% share point the same way here. USGS geology rates 95% of the county's land high radon potential. CDC also counts 31 tests taken after mitigation in Summit County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2019, with 700 tests reported; the quietest, 2014, had 139.
Summit CountyColorado, pooled
| Year | Tests | Summit County, at or above 4 pCi/L | Colorado, pooled |
|---|---|---|---|
| 2014 | 139 | 64.7% | 46.5% |
| 2015 | 242 | 59.9% | 47.2% |
| 2016 | 140 | 52.1% | 38.5% |
| 2017 | 295 | 43.1% | 41.0% |
| 2018 | 683 | 42.0% | 44.2% |
| 2019 | 700 | 39.7% | 44.1% |
| 2020 | 377 | 41.9% | 41.9% |
| 2021 | 283 | 65.4% | 47.3% |
| 2022 | 244 | 45.5% | 38.6% |
| 2023 | 295 | 38.3% | 38.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Summit County, State data
Colorado's own radon test data
MeasuredWhat Colorado's own agencies publish about radon tests in Summit 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 Summit 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
46.1%
1,715 of 3,724 tests
Median result
3.4 pCi/L
Highest result
379.3 pCi/L
Tests behind these figures
3,724 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.
Summit County, Geology
The ground under Summit County
PredictedMost of the ground under Summit County is one class on USGS's geologic map: 95.3% of its land is high radon potential, with 4.7% moderate. 95.3% of it lies in the area the map calls Rocky Mountains, to which USGS gives a radon index of 15, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Rocky Mountains | Precambrian granites, gneiss, amphibolite, variable uranium content, abundant shear zones.Sedimentary rocks shed from the granitic highlands. | High | 15 | 95.3% |
| Western Slope | Paleozoic and Mesozoic sandstone, siltstone, shale, basalt. | Moderate | 11 | 4.7% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Summit County beside the ground around it
Summit County has more high-potential ground than Colorado as a whole: 95.3% of its land against 74.8%. Of the 5 counties that border it, 3 have more high-potential ground, Clear Creek County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Summit County, Local resources
Radon testing and mitigation in Summit County
- Colorado's radon programColorado Department of Public Health and EnvironmentColorado's radon program licenses or certifies radon professionals, offers free or discounted test kits and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Colorado.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Order a discounted radon test kit
- Compare kits
- Professionals in Colorado25 professionals are listed in Colorado.
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
Summit County, Questions
Questions about radon in Summit County
Are radon levels high in Summit County?
In 2023, 38.3% of the radon tests reported to CDC for Summit County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.0 pCi/L. Of 38 Colorado counties with 30 or more tests for the same period, 21 reported a higher share; pooled, the state comes to 38.9%.
Which counties border Summit County?
Summit County borders 5 counties: Clear Creek County, Grand County, Lake County, Eagle County and Park County.
Products
Summit County, Products
Testing a home in Summit County
In Summit County, 38.3% of 295 tests reported to CDC in 2023 reached 4 pCi/L, against 38.9% pooled across Colorado. In Zone 1 the year-round level in Summit County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
Monitor
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Summit County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Summit County
Explore
Summit County, Bordering counties
Counties bordering Summit County
Calculated by Radon411- Radon levels in Park CountyEPA zone 1
57.5%at or above 4 pCi/L
Median 4.6 pCi/L · 106 tests · 19.2 points above Summit County
- Radon levels in Lake CountyEPA zone 1
54.3%at or above 4 pCi/L
Median 4.7 pCi/L · 35 tests · 16.0 points above Summit County
- Radon levels in Eagle CountyEPA zone 2
45.8%at or above 4 pCi/L
Median 3.5 pCi/L · 312 tests · 7.5 points above Summit County
- Radon levels in Grand CountyEPA zone 1
44.1%at or above 4 pCi/L
Median 3.3 pCi/L · 136 tests · 5.8 points above Summit County
- Radon levels in Clear Creek CountyEPA zone 1
41.2%at or above 4 pCi/L
Median 3.0 pCi/L · 51 tests · 2.9 points above Summit County
Summit County, Cities and towns
Cities and towns in Summit County
The Census Bureau estimates 31,517 residents in Summit County for July 1, 2025, 280 more than in 2020 (+0.9%). That works out to 52 people per square mile of land. No town dominates: Silverthorne, the largest, has 5,418 residents, 17.2% of the total. Together its 6 incorporated places hold 48.2% of those residents; the other 51.8% live outside any of them. Testing is reported here more often than across the state: CDC's 295 reported tests for 2023 come to 9.4 for every 1,000 residents (2025 estimate), against 3.6 for Colorado.
From Silverthorne to Montezuma, CDC publishes no figure by town: each reads Summit County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Silverthorne | 5,418 | +21.4% | 17.2% |
| Breckenridge | 5,015 | −0.8% | 15.9% |
| Frisco | 2,792 | −4.6% | 8.9% |
| Dillon | 1,029 | −3.0% | 3.3% |
| Blue River | 859 | −1.5% | 2.7% |
| Montezuma | 72 | −4.0% | 0.2% |
6 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Summit County, Homes
Homes in Summit County
Summit County has 31,849 homes, and many share a building: 43% are in buildings of five or more, 36% are detached houses, against 62% across Colorado. Half of its homes were built before 1989, close to Colorado's 1987: 2% date from before 1960 and 23% from 2000 or later. 69% of occupied homes are lived in by their owner (Colorado: 66%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Summit County | Colorado |
|---|---|---|
| Housing units | 31,849 | 2,545,124 |
| Detached houses | 36% | 62% |
| In buildings of 5 or more | 43% | 22% |
| Mobile homes | 1% | 4% |
| Built before 1960 | 2% | 16% |
| Built since 2000 | 23% | 31% |
| Middle year built | 1989 | 1987 |
| Owner-occupied | 69% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.