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

EPA places Holmes 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 that's the 89th percentile for radon potential — Holmes County outranks 89% of every county EPA has rated.

Holmes County by the numbers

Holmes County, Ohio is home to about 44,668 people across 422.614 square miles. Averaged across its land area, Holmes County runs about 106 people per square mile. By population, Holmes County is the 352nd largest of every county sharing its EPA zone — the 67th percentile by population within that zone. EPA's geology-based Region 5 groups Holmes County with 523 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Holmes County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. 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 Holmes County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Holmes County tests above the action level

For a Holmes 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 Holmes County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Holmes 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 Holmes 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. Whatever zone Holmes County carries, the zone explainer covers what it does and doesn't tell you about any one house.