What EPA's radon map says about Shelby County

Shelby 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 90th percentile for radon potential — Shelby County outranks 90% of every county EPA has rated.

Shelby County by the numbers

About 47,952 people live in Shelby County, Ohio, spread over 407.691 square miles. Averaged across its land area, Shelby County runs about 118 people per square mile. Among counties sharing Shelby County's EPA zone, it outranks 70% of them by population. Geologically, Shelby County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Zone vs. an actual test

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Shelby County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Shelby County will test well under the action level, and EPA's guidance is to test regardless of zone.

Next steps for a home in Shelby County

Mitigation cost doesn't depend on Shelby County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Ohio's state radon program

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

More on how this number was built

Shelby County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.