Radon levels by ZIP code: Greater Cincinnati and NKY data

Find your ZIP code below to see what radon tests in your part of Greater Cincinnati have actually measured. For each Ohio ZIP, the table gives the median result, the share of tests above EPA's 4.0 pCi/L action level, and the number of tests behind those figures. The numbers come from the Ohio Department of Health's radon dashboard, which compiles pre-mitigation results reported by Ohio-licensed radon testers and mitigation specialists since 2010. They were pulled in September 2026, and ODH updates the dashboard monthly. Ohio ZIP codes come first in numeric order, followed by Northern Kentucky.

How to read a row. The median is the middle result: half the reported tests in that ZIP fell below it and half above. The percentage is the closest thing to your odds of a result that calls for a fix. The test count tells you how much weight the other two numbers can bear, and rows built on fewer than 200 tests are marked as small samples. These are houses someone paid a licensed professional to test, often during a sale, so read them as a portrait of tested homes rather than every home.

What a county zone tells you, and what it does not. The middle column gives each county's zone on EPA's 1993 Map of Radon Zones. Zone 1 means a predicted county-wide average indoor screening level above 4 pCi/L; Zone 2 means a predicted average between 2 and 4. Hamilton, Butler, and Warren counties are Zone 1. Clermont County is Zone 2, and so are Boone, Kenton, and Campbell counties in Kentucky. EPA says the map should not be used to decide whether an individual home needs a test, and the measured data shows why: about 22 percent of Hamilton County's 42,706 reported tests read above 4.0, while Zone 2 Clermont County came in near 36 percent of 9,824.

Northern Kentucky. Kentucky publishes no comparable ZIP-level results, so the Kentucky rows list the towns each ZIP covers and the county's EPA zone. For every Ohio county's zone next to its measured results, see our Ohio radon map by county.

What to do with your ZIP code's number

No row in this table can tell you the radon level in your house. Neighbors on the same street regularly test far apart, because foundation type, cracks and sump openings, and the way a house breathes vary more from lot to lot than the soil does. Use your ZIP to set expectations, then test:

• Ohio homeowners can order a free test kit through the Ohio Department of Health at ohio.radon.com.
• Northern Kentucky homeowners can use a hardware-store kit or hire a measurement professional certified under Kentucky law (KRS 309.436); the Kentucky Board of Radon Safety links the national credential directories.
• Buying or selling? A test run for someone else must be done by an Ohio-licensed radon tester or a Kentucky-certified measurement contractor. Our radon testing page covers the professional options.

Place the kit in the lowest level you use as living space, 20 inches to 6 feet off the floor, away from the kitchen, bathroom, laundry, and sump, with windows and outside doors closed for 12 hours before the test starts. Our heating-season testing guide walks through the full setup.

If your result is 4.0 pCi/L or higher, EPA recommends a follow-up test and then a fix; between 2.0 and 4.0, it recommends considering one. The radon mitigation systems page explains how the fix works, and the radon cost calculator gives a price range for your foundation. Call or text us with your ZIP code and your result, and we will tell you what comes next.