Is Miami County, OH a radon risk area?

Miami County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Rank it against the rest of the country and Miami County lands in the 94th percentile for radon potential.

Miami County by the numbers

About 111,950 people live in Miami County, Ohio, spread over 406.581 square miles. Population density there runs about 275 people per square mile. Rank 180 by population within its EPA zone puts Miami County at the 83rd percentile among zone peers. Miami County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Miami County

Miami County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Some Miami County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

If Miami County tests above the action level

Nothing about Miami 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

Miami County's test kit answers today; a Airthings radon monitor keeps answering for Miami 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 Miami County carries, the zone explainer covers what it does and doesn't tell you about any one house.