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 Gilpin County, Colorado
EPA puts Gilpin County in Zone 1, its highest radon zone, and 26.4% of its 129 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
26.4%
12.5 pts below CO
- Gilpin
- 26.4%
- Colorado
- 38.9%
129 tests, 2023
Median result
1.1pCi/L
Below action level
- Gilpin
- 1.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
129
24th of 38 by tests
- Gilpin
- 129
- 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
35 of 38
Lowest quarter
- Gilpin
- 26.4%
- Park
- 57.5%
By share, of 38 with 30+ tests
Read a result for Gilpin County
Starts at Gilpin County's median, 1.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.1 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. Gilpin County's median reported result, 2023.
The data
Gilpin County, At a glance
Gilpin County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Gilpin 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 Gilpin County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 76.9% |
| 2015 | 50.0% |
| 2016 | 40.0% |
| 2017 | 52.0% |
| 2018 | 58.9% |
| 2019 | 64.0% |
| 2020 | 52.1% |
| 2021 | 64.4% |
| 2022 | 65.4% |
| 2023 | 26.4% |
2023: 26.4%. Across these years the share ran from 26.4% to 76.9%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 129 tests reported to CDC for Gilpin 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).
Gilpin County, Compared
Gilpin County radon figures, compared
Calculated by Radon411Gilpin County's 129 reported tests in 2023 had a middle value of 1.1 pCi/L and a maximum of 156.9 pCi/L, and 26.4% reached 4 pCi/L. Colorado as a whole (61 Colorado counties, pooled) comes to 38.9%: 12.5 points higher than here.
Among its state's counties it ranks 35th of 38 Colorado counties with 30 or more tests for the same period. Statewide for the same period, Park County reported the highest share (57.5%) and Bent County the lowest (3.7%).
Below the action level, 77 tests (59.7%) came in under 2 pCi/L, against 39.2% statewide, and 18 tests (14.0%) fell between 2 and 4, against 22.0% statewide. The busiest year on file was 2023, with 129 tests reported; the quietest, 2015, had 18.
EPA's 1993 zone map puts Gilpin County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Next door, the shares run from 34.2% in Boulder County to 44.1% in Grand County. Over 7 years of annual figures the share fell 13.6 points, from 40.0% in 2016 to 26.4% in 2023; its peak was 65.4% in 2022.
CDC also counts 6 tests taken after mitigation in Gilpin County for the same period: tests in homes where a fix was already in.
Gilpin CountyColorado, pooled
26.4% % of tests38.9% % of tests
| Year | Tests | Gilpin County, at or above 4 pCi/L | Colorado, pooled |
|---|---|---|---|
| 2016 | 40 | 40.0% | 38.5% |
| 2018 | 56 | 58.9% | 44.2% |
| 2019 | 50 | 64.0% | 44.1% |
| 2020 | 48 | 52.1% | 41.9% |
| 2021 | 59 | 64.4% | 47.3% |
| 2022 | 52 | 65.4% | 38.6% |
| 2023 | 129 | 26.4% | 38.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Gilpin County, State data
Colorado's own radon test data
MeasuredWhat Colorado's own agencies publish about radon tests in Gilpin 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 Gilpin 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
54.9%
349 of 636 tests
Median result
4.6 pCi/L
Highest result
773.9 pCi/L
Tests behind these figures
636 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.
Gilpin County, Geology
The ground under Gilpin County
PredictedUSGS's geologic map puts all of Gilpin County's mapped land in one class: high radon potential. All 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 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Gilpin County beside the ground around it
Gilpin County has more high-potential ground than Colorado as a whole: 100% of its land against 74.8%. Of the 4 counties that border it, none has as large a share of high-potential ground; Boulder County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Gilpin County, Local resources
Radon testing and mitigation in Gilpin 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
Gilpin County, Questions
Questions about radon in Gilpin County
Are radon levels high in Gilpin County?
In 2023, 26.4% of the radon tests reported to CDC for Gilpin County, Colorado were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.1 pCi/L. Of 38 Colorado counties with 30 or more tests for the same period, 34 reported a higher share; pooled, the state comes to 38.9%.
Which counties border Gilpin County?
Gilpin County borders 4 counties: Clear Creek County, Boulder County, Jefferson County and Grand County.
Products
Gilpin County, Products
Testing a home in Gilpin County
In Gilpin County, 26.4% of 129 tests reported to CDC in 2023 reached 4 pCi/L, against 38.9% pooled across Colorado. In Zone 1 the year-round level in Gilpin 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 Plus battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Approved
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 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
Gilpin County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Gilpin County
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Gilpin County, Bordering counties
Counties bordering Gilpin County
Calculated by Radon411- Radon levels in Grand CountyEPA zone 1
44.1%at or above 4 pCi/L
Median 3.3 pCi/L · 136 tests · 17.7 points above Gilpin County
- Radon levels in Jefferson CountyEPA zone 1
41.8%at or above 4 pCi/L
Median 3.2 pCi/L · 3,068 tests · 15.4 points above Gilpin County
- Radon levels in Clear Creek CountyEPA zone 1
41.2%at or above 4 pCi/L
Median 3.0 pCi/L · 51 tests · 14.8 points above Gilpin County
- Radon levels in Boulder CountyEPA zone 1
34.2%at or above 4 pCi/L
Median 2.5 pCi/L · 1,963 tests · 7.8 points above Gilpin County
Gilpin County, Cities and towns
Cities and towns in Gilpin County
The Census Bureau estimates 6,073 residents in Gilpin County for July 1, 2025, 256 more than in 2020 (+4.4%). That works out to 40 people per square mile of land. No town dominates: Black Hawk, the largest, has 120 residents, 2.0% of the total. Testing is reported here more often than across the state: CDC's 129 reported tests for 2023 come to 21.2 for every 1,000 residents (2025 estimate), against 3.6 for Colorado.
From Black Hawk to Central City, CDC publishes no figure by town: each reads Gilpin County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Black Hawk | 120 | +0.8% | 2.0% |
- Central City (part)
2 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Gilpin County, Homes
Homes in Gilpin County
Gilpin County is a place of houses on their own lots: 91% of its 3,706 homes are detached single-family houses, against 62% across Colorado. Half of its homes were built before 1982, close to Colorado's 1987: 18% date from before 1960 and 16% from 2000 or later. Owners live in 80% of the occupied homes (Colorado: 66%), so for most households a test and a fix are their own to order.
| Homes | Gilpin County | Colorado |
|---|---|---|
| Housing units | 3,706 | 2,545,124 |
| Detached houses | 91% | 62% |
| In buildings of 5 or more | 4% | 22% |
| Mobile homes | 2% | 4% |
| Built before 1960 | 18% | 16% |
| Built since 2000 | 16% | 31% |
| Middle year built | 1982 | 1987 |
| Owner-occupied | 80% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.