What the data shows
- Higher share of high results than 40 of 64 Colorado counties.
- 1.1× the Colorado rate of 46%.
- Higher than 8 of 10 neighbouring counties.
- 119.2 tests per 1,000 homes (Colorado: 91.7).
- Median result 4.0 pCi/L: at or above the 4 pCi/L action level.
How Jefferson County compares
Data table
| Area | Tests ≥ 4 pCi/L | Tests |
|---|---|---|
| Teller County | 55% | 2,727 |
| Gilpin County | 55% | 636 |
| Jefferson County | 50% | 30,229 |
| Park County | 49% | 1,064 |
| Arapahoe County | 48% | 21,419 |
| Adams County | 47% | 12,383 |
| Douglas County | 46% | 16,872 |
| Broomfield County | 44% | 4,598 |
| Boulder County | 44% | 19,914 |
| Denver County | 40% | 21,979 |
| Clear Creek County | 37% | 710 |
| Colorado (64 counties) | 46% | 237,408 |
Same source as Jefferson County.
What it means for your home
More than half of all results in Jefferson County were at or above 4 pCi/L, where the EPA recommends a fix. Only a test shows your own home's level.
Levels in pCi/L from the EPA. The WHO reference level is 100 Bq/m³, about 2.7 pCi/L.
Test your home
Start with a short-term test (2–90 days) and confirm a result of 4 pCi/L or more with a second test. EPA guide
Sponsored: we earn a commission on purchases through these links. We haven't tested Airthings monitors yet.
Prefer a digital monitor? See Airthings radon monitors, or enter code radonbycounty-10OFF at their discount store for 10% off.
Fixing high radon
No local job records yet. National range: $800–$2,500, average $1,200 (EPA, 2003). Cost guide →
Colorado licenses radon mitigators. Source
Buying or selling here
Since August 2023, Colorado home sale contracts must include the seller's known radon test, report and mitigation history and the state health department's radon brochure (SB23-206). Source
Checked against the official text on 2026-11-03. Not legal advice.
About this data
Source: Colorado county radon test results (Colorado Department of Public Health and Environment). Period: 2005–2025. Tests: 30,229. Read the methodology →
These are voluntary and real-estate tests, not a random sample of homes, so they describe tested homes rather than every home.
About this page
Published by Ray Roman, editor of Radon by County. Figures are loaded from the cited source and spot-checked against it. Editorial policy · About us