Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Ouray County, Colorado
EPA puts Ouray County in Zone 1, its highest radon zone, and 37.2% of its 43 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
37.2%
1.7 pts below CO
- Ouray
- 37.2%
- Colorado
- 38.9%
43 tests, 2023
Median result
1.2pCi/L
Below action level
- Ouray
- 1.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
43
35th of 38 by tests
- Ouray
- 43
- 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
24 of 38
Middle half
- Ouray
- 37.2%
- Park
- 57.5%
By share, of 38 with 30+ tests
Read a result for Ouray County
Starts at Ouray County's median, 1.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.2 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Ouray County's median reported result, 2023.
The data
Ouray County, At a glance
Ouray County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Ouray County in
USGS geologic potential: High across 61% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Ouray County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 69.2% |
| 2015 | 61.5% |
| 2018 | 69.0% |
| 2019 | 52.4% |
| 2020 | 54.3% |
| 2021 | 37.5% |
| 2022 | 40.0% |
| 2023 | 37.2% |
2023: 37.2%. Across these years the share ran from 37.2% to 69.2%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 43 tests reported to CDC for Ouray 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).
Ouray County, Compared
Ouray County radon figures, compared
Calculated by Radon411In Ouray County, about 4 in 10 reported tests in 2023 (16 of 43) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 3.8 points higher. Across 61 Colorado counties pooled together, 38.9% of tests reached that level, so Ouray County runs 1.7 points below its state.
Of 2 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 34.7% (Gunnison County) to 55.3% (Montrose County). By share, Ouray County is 24th of 38 Colorado counties with 30 or more tests for the same period.
Year by year, 2018 opened at 69.0% and 2023 closed at 37.2% (down 31.8 points), with 2018 the high at 69.0%. Half the tests came in under 1.2 pCi/L and half over it; the single highest reached 25.5 pCi/L. Below the action level, 24 tests (55.8%) came in under 2 pCi/L, against 39.2% statewide, and 3 tests (7.0%) fell between 2 and 4, against 22.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 37.2% share point the same way here. USGS geology rates 61% of the county's land high radon potential.
The busiest year on file was 2018, with 100 tests reported; the quietest, 2022, had 10.
Ouray CountyColorado, pooled
| Year | Tests | Ouray County, at or above 4 pCi/L | Colorado, pooled |
|---|---|---|---|
| 2018 | 100 | 69.0% | 44.2% |
| 2019 | 63 | 52.4% | 44.1% |
| 2020 | 35 | 54.3% | 41.9% |
| 2021 | 32 | 37.5% | 47.3% |
| 2023 | 43 | 37.2% | 38.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Ouray County, State data
Colorado's own radon test data
MeasuredWhat Colorado's own agencies publish about radon tests in Ouray 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 Ouray 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
49.5%
151 of 305 tests
Median result
3.8 pCi/L
Highest result
230.0 pCi/L
Tests behind these figures
305 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.
Ouray County, Geology
The ground under Ouray County
PredictedUSGS's geologic map splits Ouray County: 61.3% of its land is high radon potential and 38.7% moderate. The map puts 46.4% of Ouray County in the area it calls Uravan Belt and 38.7% in San Juan Volcanic field, with one smaller area beside them. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Uravan Belt | Uranium-bearing Cretaceous and Jurassic sedimentary rocks of the Uravan mineral belt. | High | 13 | 46.4% |
| San Juan Volcanic field | Volcanic rocks, rhyolite, tuff, basalt | Moderate | 11 | 38.7% |
| Mancos Shale Lowlands | Marine shales (Mancos Shale) and Tertiary sandstones. | High | 13 | 14.9% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Ouray County beside the ground around it
Colorado as a whole has more high-potential ground than Ouray County: 74.8% of its land, against 61.3% here. Of the 5 counties that border it, 3 have more high-potential ground, Montrose County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Ouray County, Local resources
Radon testing and mitigation in Ouray 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
Ouray County, Questions
Questions about radon in Ouray County
Are radon levels high in Ouray County?
In 2023, 37.2% of the radon tests reported to CDC for Ouray County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.2 pCi/L. Of 38 Colorado counties with 30 or more tests for the same period, 23 reported a higher share; pooled, the state comes to 38.9%.
Which counties border Ouray County?
Ouray County borders 5 counties: San Juan County, Hinsdale County, Montrose County, San Miguel County and Gunnison County.
Products
Ouray County, Products
Testing a home in Ouray County
In Ouray County, 37.2% of 43 tests reported to CDC in 2023 reached 4 pCi/L, against 38.9% pooled across Colorado. In Zone 1 the year-round level in Ouray 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
MonitorForensics Detectors
FD-65-RADON rechargeable radon detector with a color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Ouray County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Ouray County
Explore
Ouray County, Bordering counties
Counties bordering Ouray County
Calculated by Radon411- Radon levels in Hinsdale CountyEPA zone 2
100.0%at or above 4 pCi/L
Median 6.8 pCi/L · 1 test · 62.8 points above Ouray County
- Radon levels in Montrose CountyEPA zone 1
55.3%at or above 4 pCi/L
Median 4.5 pCi/L · 215 tests · 18.1 points above Ouray County
- Radon levels in San Juan CountyEPA zone 2
46.2%at or above 4 pCi/L
Median 3.6 pCi/L · 13 tests · 9.0 points above Ouray County
- Radon levels in San Miguel CountyEPA zone 1
37.5%at or above 4 pCi/L
Median 3.4 pCi/L · 16 tests · 0.3 points above Ouray County
- Radon levels in Gunnison CountyEPA zone 1
34.7%at or above 4 pCi/L
Median 2.5 pCi/L · 147 tests · 2.5 points below Ouray County
Ouray County, Cities and towns
Cities and towns in Ouray County
Ouray County is growing: the Census Bureau puts it at 5,265 residents on July 1, 2025, up 7.9% from 4,879 in 2020. Spread over its land, that is 9.7 people to the square mile. Its largest town, Ridgway, has 1,324 residents, 25.1% of the total. Together its 2 incorporated places hold 42.8% of those residents; the other 57.2% live outside any of them. Testing is reported here more often than across the state: CDC's 43 reported tests for 2023 come to 8.2 for every 1,000 residents (2025 estimate), against 3.6 for Colorado.
From Ridgway to Ouray, CDC publishes no figure by town: each reads Ouray County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Ridgway | 1,324 | +12.2% | 25.1% |
| Ouray | 929 | +3.3% | 17.6% |
2 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).
Ouray County, Homes
Homes in Ouray County
Of Ouray County's 3,466 homes, 74% are detached houses, against 62% across Colorado; 9% are in buildings of five or more homes. Half of its homes were built before 1994, close to Colorado's 1987: 16% date from before 1960 and 39% from 2000 or later. Owners live in 78% of the occupied homes (Colorado: 66%), so for most households a test and a fix are their own to order.
| Homes | Ouray County | Colorado |
|---|---|---|
| Housing units | 3,466 | 2,545,124 |
| Detached houses | 74% | 62% |
| In buildings of 5 or more | 9% | 22% |
| Mobile homes | 6% | 4% |
| Built before 1960 | 16% | 16% |
| Built since 2000 | 39% | 31% |
| Middle year built | 1994 | 1987 |
| Owner-occupied | 78% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.