Colorado · Arapahoe County
Radon Levels in Arapahoe County, Colorado
In Arapahoe County, Colorado, 48.4% of pre-mitigation home radon tests came back at or above the EPA action level of 4 pCi/L — based on 19,356 tests collected by the Colorado Department of Public Health and Environment between 2005 and 2024. The county’s median pre-mitigation reading was 3.8 pCi/L, with a maximum recorded result of 369.6 pCi/L.
EPA recommends mitigation when long-term indoor radon measures at or above 4 pCi/L. Counties with elevated medians and large test counts — like Arapahoe — typically warrant testing during real-estate transactions and seasonal retesting in occupied homes.
Arapahoe County by the numbers
Source: Colorado Department of Public Health and Environment. Pre-mitigation indoor radon tests, 2005–2024.
- Tests above 4 pCi/L
- 48.4%
- Total tests recorded
- 19,356
- Median result
- 3.8 pCi/L
- Maximum recorded
- 369.6 pCi/L
EPA action level
CDPHE 2005–2024
pre-mitigation
outlier high
How Arapahoe compares to Colorado as a whole
Both bars show the percentage of pre-mitigation tests that came back at or above the EPA action level of 4 pCi/L.
CDPHE 2005–2024
Get a free quote for radon mitigation in Arapahoe County.
We’re NRPP-certified and Colorado state-licensed. A typical sub-slab depressurization install runs about $1,500 and reduces indoor radon by 95%+ in most Arapahoe County homes.
- 24-hour quote turnaround
- Installed in 4–6 hours
- Post-install re-test included
- Radon-mitigation listing feature
Or call us at (866) 398-9858 — same-day response during business hours.
Prefer the data first? Download the free Colorado Radon Risk Map.
Arapahoe County radon questions
- What level of radon is dangerous?
- The EPA recommends mitigation at 4 pCi/L or higher. Between 2 and 4 pCi/L, you should consider mitigation — long-term exposure at this range still carries lung-cancer risk. Below 2 pCi/L, the EPA suggests retesting every two years.
- How much does radon mitigation cost in Colorado?
- A standard sub-slab depressurization system in Colorado typically runs $1,200–$2,500, with $1,500 the most common all-in price. That single system reduces indoor radon by 95% or more in the majority of homes. Crawlspace installs cost more ($2,000–$5,000) because the membrane and tie-ins are more involved.
- Why are radon levels elevated in Arapahoe County?
- Geology drives most of it. Granitic bedrock and uranium-bearing soils — common across Colorado — release radon as they decay, and Front Range building style (basements, tight envelopes, forced-air systems) concentrates that gas indoors. Higher-elevation counties also tend to have lower atmospheric pressure, which can pull radon up through the foundation more aggressively.