Douglas County, CO radon potential
Douglas County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Douglas County ranks higher in radon potential than 98% of rated counties (the 98th percentile).
How Douglas County compares
Douglas County, Colorado is home to about 393,995 people across 840.888 square miles. That works out to roughly 469 people per square mile. Within its own EPA zone, Douglas County is bigger by population than 95% of the counties that share it. EPA's geology-based Region 8 groups Douglas County with 290 other counties nationally sharing its underlying rock and soil profile.
Why the zone isn't the answer by itself
Where the national indoor average runs about 1.3 pCi/L, Douglas County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Douglas County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.
Testing and mitigation in Douglas County
A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.
Find Colorado's state radon program
For Douglas County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Douglas County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.
Where Douglas County's figures come from
Douglas County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Douglas County carries, the zone explainer covers what it does and doesn't tell you about any one house.