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

Butler County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 98th percentile for radon potential — Butler County outranks 98% of every county EPA has rated.

Butler County by the numbers

Butler County, Ohio is home to about 399,542 people across 466.531 square miles. Population density there runs about 856 people per square mile. By population, Butler County is the 54th largest of every county sharing its EPA zone — the 95th percentile by population within that zone. Geologically, Butler County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

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 Butler County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Butler County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Butler County tests above the action level

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

Where Butler 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. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.