Is Darke County, OH a radon risk area?

EPA's own radon map rates Darke County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Rank it against the rest of the country and Darke County lands in the 90th percentile for radon potential.

Where Darke County sits nationally

About 51,462 people live in Darke County, Ohio, spread over 598.102 square miles. Averaged across its land area, Darke County runs about 86 people per square mile. Rank 307 by population within its EPA zone puts Darke County at the 71st percentile among zone peers. Darke County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Darke County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Darke County specifically.

If Darke County tests above the action level

Nothing about Darke 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 Ohio's state radon program

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

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Darke County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.