Greene County, OH: EPA's radon zone, explained

EPA places Greene County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally, Greene County ranks higher in radon potential than 97% of rated counties (the 97th percentile).

Greene County by the numbers

Greene County, Ohio is home to about 172,347 people across 413.632 square miles. That works out to roughly 417 people per square mile. By population, Greene County is the 110th largest of every county sharing its EPA zone — the 90th percentile by population within that zone. Geologically, Greene County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Zone vs. an actual test

Greene 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 Greene 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.

Testing and mitigation in Greene County

For a Greene County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Ohio's state radon program

For Greene County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Greene County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Greene County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.