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 Delta County, Colorado
EPA puts Delta County in Zone 1, its highest radon zone, and high results are common there: 55.6% of the 124 radon tests reported to CDC (2023) came back 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
55.6%
16.7 pts above CO
- Delta
- 55.6%
- Colorado
- 38.9%
124 tests, 2023
Median result
4.6pCi/L
Action level reached
- Delta
- 4.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
124
25th of 38 by tests
- Delta
- 124
- 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
3 of 38
Top quarter
- Delta
- 55.6%
- Park
- 57.5%
By share, of 38 with 30+ tests
Read a result for Delta County
Starts at Delta County's median, 4.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.6 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Delta County's median reported result, 2023.
The data
Delta County, At a glance
Delta County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Delta County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Delta County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 48.1% |
| 2015 | 47.1% |
| 2016 | 31.3% |
| 2017 | 35.7% |
| 2018 | 44.0% |
| 2019 | 61.8% |
| 2020 | 59.5% |
| 2021 | 60.5% |
| 2022 | 48.9% |
| 2023 | 55.6% |
2023: 55.6%. Across these years the share ran from 31.3% to 61.8%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 124 tests reported to CDC for Delta 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).
Delta County, Compared
Delta County radon figures, compared
Calculated by Radon411More than half: 55.6% of the 124 radon tests reported to CDC for Delta County in 2023 read at least 4 pCi/L. That places it 3rd of 38 Colorado counties with 30 or more tests for the same period. That is 16.7 points above the 38.9% pooled from 61 Colorado counties.
The median result, 4.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 44.4 pCi/L. The rest split 16.9% under 2 pCi/L and 27.4% from 2 to 4 (Colorado: 39.2% and 22.0%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 55.6% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Montrose County at 55.3%, the lowest Mesa County at 18.9%. Statewide for the same period, Park County reported the highest share (57.5%) and Bent County the lowest (3.7%).
The busiest year on file was 2019, with 178 tests reported; the quietest, 2014, had 27.
Over 9 years of annual figures the share rose 8.5 points, from 47.1% in 2015 to 55.6% in 2023; its peak was 61.8% in 2019. Nationally, every county with a figure for the same period pools to 33.4%; Delta County sits 22.2 points above it. CDC also counts 6 tests taken after mitigation in Delta County for the same period: tests in homes where a fix was already in.
Delta CountyColorado, pooled
55.6% % of tests38.9% % of tests
| Year | Tests | Delta County, at or above 4 pCi/L | Colorado, pooled |
|---|---|---|---|
| 2015 | 51 | 47.1% | 47.2% |
| 2016 | 32 | 31.3% | 38.5% |
| 2017 | 42 | 35.7% | 41.0% |
| 2018 | 168 | 44.0% | 44.2% |
| 2019 | 178 | 61.8% | 44.1% |
| 2020 | 163 | 59.5% | 41.9% |
| 2021 | 81 | 60.5% | 47.3% |
| 2022 | 90 | 48.9% | 38.6% |
| 2023 | 124 | 55.6% | 38.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Delta County, State data
Colorado's own radon test data
MeasuredWhat Colorado's own agencies publish about radon tests in Delta 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 Delta 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
54.7%
470 of 859 tests
Median result
4.5 pCi/L
Highest result
209.0 pCi/L
Tests behind these figures
859 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.
Delta County, Geology
The ground under Delta County
PredictedUSGS's geologic map puts all of Delta County's mapped land in one class: high radon potential. The map puts 67.1% of Delta County in the area it calls Mancos Shale Lowlands and 24.2% in Paradox Basin, with one smaller area beside them. USGS gives both a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Mancos Shale Lowlands | Marine shales (Mancos Shale) and Tertiary sandstones. | High | 13 | 67.1% |
| Paradox Basin | Tertiary sandstone, siltstone and shale. | High | 13 | 24.2% |
| Uravan Belt | Uranium-bearing Cretaceous and Jurassic sedimentary rocks of the Uravan mineral belt. | High | 13 | 8.7% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Delta County beside the ground around it
Delta County has more high-potential ground than Colorado as a whole: 100% of its land against 74.8%. Of the 3 counties that border it, none has as large a share of high-potential ground; Montrose County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Delta County, Local resources
Radon testing and mitigation in Delta 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
Delta County, Questions
Questions about radon in Delta County
Are radon levels high in Delta County?
In 2023, 55.6% of the radon tests reported to CDC for Delta County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.6 pCi/L. Of 38 Colorado counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 38.9%.
Which counties border Delta County?
Delta County borders 3 counties: Mesa County, Montrose County and Gunnison County.
Products
Delta County, Products
Testing a home in Delta County
In Delta County, 55.6% of 124 tests reported to CDC in 2023 reached 4 pCi/L, against 38.9% pooled across Colorado. In Zone 1 the year-round level in Delta 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
MonitorAranet
Radon One battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 minutes
Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Delta County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Delta County
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Delta County, Bordering counties
Counties bordering Delta County
Calculated by Radon411- Radon levels in Montrose CountyEPA zone 1
55.3%at or above 4 pCi/L
Median 4.5 pCi/L · 215 tests · 0.3 points below Delta County
- Radon levels in Gunnison CountyEPA zone 1
34.7%at or above 4 pCi/L
Median 2.5 pCi/L · 147 tests · 20.9 points below Delta County
- Radon levels in Mesa CountyEPA zone 1
18.9%at or above 4 pCi/L
Median 2.2 pCi/L · 567 tests · 36.7 points below Delta County
Delta County, Cities and towns
Cities and towns in Delta County
The Census Bureau estimates 32,178 residents in Delta County for July 1, 2025, 1,116 more than in 2020 (+3.6%). That works out to 28 people per square mile of land. Its largest town, Delta, has 9,802 residents, 30.5% of the total. Together its 6 incorporated places hold 57.1% of those residents; the other 42.9% live outside any of them. CDC's 124 reported tests for 2023 work out to 3.9 per 1,000 residents (2025 estimate), close to Colorado's 3.6.
From Delta to Crawford, CDC publishes no figure by town: each reads Delta County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Delta | 9,802 | +8.3% | 30.5% |
| Orchard City | 3,299 | +4.9% | 10.3% |
| Cedaredge | 2,448 | +7.2% | 7.6% |
| Paonia | 1,477 | +1.7% | 4.6% |
| Hotchkiss | 945 | +6.7% | 2.9% |
| Crawford | 411 | +3.0% | 1.3% |
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).
Delta County, Homes
Homes in Delta County
Delta County is a place of houses on their own lots: 77% of its 14,931 homes are detached single-family houses, against 62% across Colorado. The homes are older than Colorado's as a whole: half were built before 1979 (1987 for Colorado), and 26% date from before 1960. Owners live in 76% of the occupied homes (Colorado: 66%), so for most households a test and a fix are their own to order.
| Homes | Delta County | Colorado |
|---|---|---|
| Housing units | 14,931 | 2,545,124 |
| Detached houses | 77% | 62% |
| In buildings of 5 or more | 3% | 22% |
| Mobile homes | 14% | 4% |
| Built before 1960 | 26% | 16% |
| Built since 2000 | 24% | 31% |
| Middle year built | 1979 | 1987 |
| Owner-occupied | 76% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.