Is Douglas County, SD a radon risk area?

Douglas County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Douglas County sits at the 69th percentile nationally for radon potential — above 69 of every 100 rated counties.

How Douglas County compares

About 2,849 people live in Douglas County, South Dakota, spread over 431.801 square miles. That works out to roughly 7 people per square mile. Rank 986 by population within its EPA zone puts Douglas County at the 7th percentile among zone peers. EPA's geology-based Region 8 groups Douglas County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Douglas County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Douglas County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. That doesn't mean every Douglas County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Douglas County

Nothing about Douglas County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find South Dakota's state radon program

Douglas County's test kit answers today; a Airthings radon monitor keeps answering for Douglas County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

Douglas County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.