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, depending on home size, foundation type, and venting path. 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 Douglas 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.

Colorado · Douglas County

Radon Mitigation & Testing in Douglas County, Colorado

Name: Colorado Pre-Mitigation Indoor Radon Test Results, 2005–2024
Creator: Colorado Department of Public Health and Environment
License: https://creativecommons.org/publicdomain/zero/1.0/

In Douglas County, Colorado, 47.1% of pre-mitigation home radon tests came back at or above the EPA action level of 4 pCi/L — based on 15,079 tests collected by the Colorado Department of Public Health and Environment between 2005 and 2024. The county’s median pre-mitigation reading was 3.6 pCi/L, with a maximum recorded result of 274 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 Douglas — typically warrant testing during real-estate transactions and seasonal retesting in occupied homes.

Colorado Radon Check services Douglas County

Douglas County by the numbers

Source: Colorado Department of Public Health and Environment. Pre-mitigation indoor radon tests, 2005–2024.

Tests above 4 pCi/L: 47.1%
Total tests recorded: 15,079
Median result: 3.6 pCi/L
Maximum recorded: 274 pCi/L

How Douglas 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.

Douglas County47.1%

Colorado statewide46.9%

CDPHE 2005–2024

Douglas County tests 0.2 percentage points higher than the statewide average.

Colorado Radon Check services Douglas County

Get a free quote for radon mitigation in Douglas County.

We’re NRPP-certified and Colorado state-licensed. A standard sub-slab depressurization install reduces indoor radon by 95%+ in most Douglas County homes — exact quote in 24 hours.

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.

We service these Douglas County cities & towns

Castle Rock
Highlands Ranch
Parker
Lone Tree
Castle Pines
Larkspur
Sedalia
Roxborough Park

If you live in or near any of these, we cover you. Outside the Front Range service area? See the section below for an NRPP referral.

Douglas 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, depending on home size, foundation type, and venting path. 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 Douglas 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.

Nearby

Radon data for counties near Douglas

Radon risk varies by geology, not by county line. Check the data for neighboring Colorado counties:

Percentage shown = share of pre-mitigation tests at or above the EPA 4 pCi/L action level. FR tags mark Front Range counties we service directly.