Is Custer County, OK a radon risk area?

EPA places Custer County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Custer County in the 17th percentile nationally for radon potential — higher than 17% of the counties EPA has rated.

Where Custer County sits nationally

About 28,266 people live in Custer County, Oklahoma, spread over 988.779 square miles. That works out to roughly 29 people per square mile. Rank 506 by population within its EPA zone puts Custer County at the 51st percentile among zone peers. Geologically, Custer County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

What this actually means for a house in Custer County

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Custer County's Zone 3 prediction is the low end of the scale. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Custer County testing above the action level often enough that skipping a test isn't the safe assumption.

If Custer County tests above the action level

Nothing about Custer 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 Oklahoma's state radon program

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Custer County carries, the zone explainer covers what it does and doesn't tell you about any one house.