Radon Risk in Ohio
EPA zone data and CDC radon averages for all 88 counties in Ohio.
Tipper on radon in Ohio
Ohio has a statewide average radon level of 7.46 pCi/L, above the EPA's action level of 4 pCi/L. That puts Ohio among the higher-risk states in the country for indoor radon. If you live here, testing your home is genuinely important.
Looking at the zone breakdown: 53 of Ohio's 88 counties are EPA Zone 1 (high risk), 35 are Zone 2 (moderate). That means 60% of the state falls into the highest risk category, counties where the EPA predicts average indoor levels above 4 pCi/L. Use the county list below to find your area and see the most specific data available.
Within Ohio, the spread is notable. Knox County has the highest measured average in the state at 23.6 pCi/L. Meigs County sits at the other end with 2.8 pCi/L. 79 counties have a measured average above 4 pCi/L. Remember: these are averages. Individual homes can test significantly higher or lower than their county average depending on construction, foundation type, and ventilation.
Tipper's recommendation for Ohio residents: if you haven't tested your home, start there. A short-term test kit costs around $15 and gives you a result in 48 hours. If your home tests at or above 4 pCi/L, a professional mitigation system (typically $800–$2,000 depending on your foundation and home size) will reliably bring levels down.
Sources: EPA Radon Zone Map, CDC Environmental Public Health Tracking Network
Why Ohio's Geology Matters
Ohio has significant radon risk driven by its glacial geology. The glacial till that covers the western two-thirds of the state, combined with underlying limestone and shale bedrock, creates widespread radon production. The Devonian Ohio Shale in the northeast is particularly uranium-rich. Southeastern Ohio's unglaciated plateau generally has lower but variable risk.
Radon Disclosure Laws
Ohio's Residential Property Disclosure Form requires sellers to disclose known radon conditions, including test results and the presence of mitigation systems.
State Radon Program
Ohio Department of Health — Radon Program
Ohio has one of the highest percentages of Zone 1 counties east of the Mississippi.
Highest Radon Averages
Lowest Radon Averages
All Counties in Ohio
Click any county to see its full radon data and local contractors.
Showing 88 of 88 counties in Ohio. Zone classifications from the EPA. Average pCi/L from CDC tracking data.
Not sure where to start?
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Contractors
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