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 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.

Colorado · Arapahoe County

Radon Mitigation & Testing in Arapahoe 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 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.

Colorado Radon Check services Arapahoe County

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

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.

Arapahoe County48.4%

Colorado statewide46.9%

CDPHE 2005–2024

Arapahoe County tests 1.5 percentage points higher than the statewide average.

Colorado Radon Check services Arapahoe County

Get a free quote for radon mitigation in Arapahoe County.

We’re NRPP-certified and Colorado state-licensed. A standard sub-slab depressurization install reduces indoor radon by 95%+ in most Arapahoe 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 Arapahoe County cities & towns

Aurora
Centennial
Englewood
Greenwood Village
Littleton (east)
Cherry Hills Village
Sheridan
Glendale
Foxfield

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.

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, 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 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.

Nearby

Radon data for counties near Arapahoe

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.