Listed for: Mitigation
Licenses on file: see the profile
Locations and reports
Radon in Fort Collins, Colorado
EPA puts Larimer County, where Fort Collins is, in Zone 1, its highest radon zone, and high results are common there: 49.4% of the 1,902 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
49.4%
10.5 pts above CO
- Larimer
- 49.4%
- Colorado
- 38.9%
Larimer, 9th of 38 in CO, 2023
Median result
3.8pCi/L
Below action level
- Larimer
- 3.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Larimer's tests, 2023
Nearest county
34.2%
Boulder, 35 miles
- Boulder
- 34.2%
- Larimer
- 49.4%
1,963 tests, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
Larimer, where Fort Collins is
Tests reported
1,902
In Larimer
- Larimer
- 1,902
- Boulder
- 1,963
Reported to CDC before any fix, 2023
Read a result for Fort Collins
Starts at Larimer County's median, 3.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.8 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. Larimer County's median reported result, 2023.
The data
Fort Collins, What is published
What is published for Fort Collins
Information:
Every figure for Fort Collins is a county's
Radon data is published by county, not by city, so for Fort Collins it is Larimer County's: its EPA zone (Zone 1) and the 1,902 tests reported to CDC for 2023. Only a test tells you about one home.
Fort Collins covers 57.2 square miles of land, all of it in Larimer County. About 171,500 people live there, 2,998 to the square mile.
Fort Collins, Counties
The county Fort Collins lies in
MeasuredLarimer County's EPA zone and the figures CDC publishes for it, 2023.
Larimer CountyZone 1Highest predicted potential
- 49.4%
- Reported tests at or above 4 pCi/L
- 3.8 pCi/L
- Median reported result
- 1,902 tests
- Tests reported to CDC
- 10
- Annual years on file
Larimer County ranks 9th of 38 Colorado counties with 30 or more tests for that period, 10.5 points above the 38.9% pooled across Colorado's counties, 16.0 points above the national pool of 33.4%.
The counties nearest Fort Collins with a CDC figure for 2023, measured from the middle of the city: Boulder County (35 miles, 34.2% of 1,963 tests), Weld County (35 miles, 46.0% of 663 tests) and Broomfield County (41 miles, 36.9% of 758 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 26.4% to 46.0%; the farthest of them, Clear Creek County, is 67 miles away at 41.2%.
The directory lists 2 businesses with an address in Fort Collins, 2 for mitigation. Colorado's other cities with a page of their own: Colorado Springs, Grand Junction, Aurora and Longmont.
The counties around Fort Collins
By distance from the middle of Fort Collins; counties with 30 or more tests.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.
Fort Collins, Geology
The ground under Fort Collins
PredictedUSGS's geologic map puts all of Fort Collins' mapped land in one class: high radon potential. The map puts 62.0% of Fort Collins in the area it calls High Plains and 38.0% in Rocky Mountains. USGS gives the first a radon index of 12 and the second 15, both in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| High Plains | Quaternary deposits and Cretaceous marine shales that locally have a high radiometric signature. | High | 12 | 62.0% |
| Rocky Mountains | Precambrian granites, gneiss, amphibolite, variable uranium content, abundant shear zones.Sedimentary rocks shed from the granitic highlands. | High | 15 | 38.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Fort Collins beside its county and Colorado
The ground under Fort Collins is close to Larimer County's as a whole: 100% rated high against 98.4%. Fort Collins has more high-potential ground than Colorado as a whole: 100% of its land against 74.8%.
The map rates the ground, not the air in any home.
Fort Collins, Homes
Homes in Fort Collins
Fewer than six in ten of Fort Collins' 73,332 homes are detached houses (53%, against 65% across Larimer County); the rest are attached, in shared buildings or mobile. Half of its homes were built before 1992, close to Larimer County's 1993: 9% date from before 1960 and 35% from 2000 or later. 52% of occupied homes are lived in by their owner (Larimer County: 64%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Fort Collins | Larimer County | Colorado |
|---|---|---|---|
| Housing units | 73,332 | 161,882 | 2,545,124 |
| Detached houses | 53% | 65% | 62% |
| In buildings of 5 or more | 28% | 18% | 22% |
| Mobile homes | 2% | 3% | 4% |
| Built before 1960 | 9% | 10% | 16% |
| Built since 2000 | 35% | 37% | 31% |
| Middle year built | 1992 | 1993 | 1987 |
| Owner-occupied | 52% | 64% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.
Local help
Fort Collins, Professionals
Radon professionals listed in Fort Collins
Businesses whose listed city is Fort Collins, from the state registries and listings in the Radon411 directory, with the same business and certification status the directory shows.
Radon professionals listed in Fort Collins: 1 of 2
2 listings with Fort Collins as the city. See radon mitigation in Fort Collins, or all radon professionals in Colorado.
Fort Collins, Local resources
Local resources for Fort Collins
Who to ask in Colorado: its radon program, test kits and professionals.
What it means
Fort Collins, Questions
Questions about radon in Fort Collins
What radon zone is Fort Collins in?
Fort Collins takes its zone from Larimer County, which EPA puts in Zone 1, the map's highest class: a predicted county average above 4 pCi/L.
What are radon levels in Fort Collins?
49.4% of the 1,902 tests reported from Larimer County for 2023 were at or above 4 pCi/L, the level at which EPA says to fix a home: high results are ordinary around Fort Collins. The median reported result was 3.8 pCi/L.
Should I test my home in Fort Collins?
Yes. About 940 of the 1,902 tests reported from Larimer County were at or above 4 pCi/L. That is above Colorado's pooled 38.9%, and ranks Larimer County 9th of the 38 Colorado counties with 30 or more tests. No map says which homes those are. How to test a home.
What ground is Fort Collins built on, as far as radon goes?
62.0% of Fort Collins sits on what USGS's map calls "High Plains", rated high for radon potential, radon index 12; another 38.0% is "Rocky Mountains", in the same class.
Is radon higher in the counties around Fort Collins?
No. Larimer County's 49.4% is above every one of the 8 nearest counties with a figure: the closest share to it is Weld County (46.0%, 35 miles off), the lowest Gilpin County (26.4%, 53 miles off).
Who tests for or fixes radon in Fort Collins?
Radon411's directory has 2 businesses with an address in Fort Collins, all listed for mitigation, none for testing. Every entry names the public list it was taken from. Radon professionals in Fort Collins.
The answers use the published figures of Larimer County, the county Fort Collins lies in.
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