Radon Testing in Cincinnati

Updated October 2026 · 7 public sources cited

Hamilton County is in EPA's highest radon zone, and ODH says a test is the only way to know your level. Here's how to get a kit and what to do with the result.

Why test in Hamilton County

EPA places Hamilton County in Zone 1, the category with the highest predicted indoor radon. Neighboring Butler and Warren counties are also Zone 1, and Clermont County is Zone 2.³ EPA estimates the average U.S. indoor level is about 1.3 pCi/L, and outdoor air is about 0.4 pCi/L.⁴

Who can test your home

• You. Ohio's license law doesn't apply to owners or tenants testing a building they own or lease.⁵
• A licensed tester. Anyone else performing radon tests in Ohio, or giving expert advice on testing or radon health risks, needs an ODH tester or mitigation specialist license.⁵
• Kentucky side. In Northern Kentucky, testers fall under the Kentucky Board of Radon Safety.⁶

Picking a test

EPA says short-term tests stay in the home for 2 to 90 days. Common types are charcoal canisters, alpha track, electret ion chambers, continuous monitors and charcoal liquid scintillation detectors. Long-term tests run more than 90 days and better reflect your year-round average.⁴

EPA's three steps

1. Take a short-term test.If it's 4 pCi/L or higher, follow up.⁴
2. Follow up.Use a long-term test for the clearest picture, or a second short-term test if you need results fast. If the first result is more than twice 4 pCi/L, do the second short-term test right away.⁴
3. Decide.Fix the home if a long-term result is 4 or more, or consider fixing if two short-term tests average 4 or more.⁴

Getting a valid result

• Keep windows and outside doors closed as much as possible. For a 2–3 day test, close them 12 hours before starting.⁴
• Don't run fans that bring in outside air. Recirculating HVAC fans are fine.⁴
• Put the kit on the lowest lived-in level, in a regularly used room that isn't a kitchen or bathroom, at least 20 inches off the floor and away from drafts, heat, humidity and exterior walls.⁴
• Mail it to the lab right away when the test ends. EPA says results usually come back within a few weeks.⁴

Results and Ohio home sales

Ohio's Residential Property Disclosure Form asks whether the seller knows of radon gas and, if so, the level if known.⁷ ODH offers a downloadable booklet on radon for people buying or selling a home.¹

Please note: Ohio requires a license to give professional or expert advice on radon testing, exposure or mitigation. This page is general information summarized from public agencies, not professional advice. For advice about your home, talk with an ODH-licensed professional.