Radon zones in Ohio
Last updated
EPA’s Map of Radon Zones places 88 Ohio counties in its three radon potential zones: 53 in Zone 1 (highest), 35 in Zone 2 (moderate), and 0 in Zone 3 (low).
What this means for Ohio homes
Most Ohio counties fall in Zone 1. EPA predicts average indoor screening levels above 4 pCi/L across much of Ohio, so elevated radon is common. Testing is especially worthwhile here, and radon-resistant construction features make sense for new homes.
EPA’s guidance is the same everywhere: test your home, fix it if the level is 4 pCi/L or higher, and consider fixing between 2 and 4 pCi/L. The zone map is from 1993 and should not be used to decide whether a single home needs testing.
Ohio radon program
EPA lists the following state contact for Ohio: OH Department of Health, Radon Education and Licensing Program, phone 614-644-3020. Website: odh.ohio.gov/wps/portal/gov/odh/know-our-programs/radon-education-and-licensing-program/welcome-to. State programs can tell you about local testing data, free or discounted test kits, disclosure rules for home sales, and credentialed radon professionals.
Ohio counties and their EPA radon zones
| County | EPA radon zone |
|---|---|
| Adams County | Zone 1 |
| Allen County | Zone 1 |
| Ashland County | Zone 1 |
| Ashtabula County | Zone 2 |
| Athens County | Zone 2 |
| Auglaize County | Zone 1 |
| Belmont County | Zone 1 |
| Brown County | Zone 2 |
| Butler County | Zone 1 |
| Carroll County | Zone 1 |
| Champaign County | Zone 1 |
| Clark County | Zone 1 |
| Clermont County | Zone 2 |
| Clinton County | Zone 1 |
| Columbiana County | Zone 1 |
| Coshocton County | Zone 1 |
| Crawford County | Zone 1 |
| Cuyahoga County | Zone 2 |
| Darke County | Zone 1 |
| Defiance County | Zone 2 |
| Delaware County | Zone 1 |
| Erie County | Zone 2 |
| Fairfield County | Zone 1 |
| Fayette County | Zone 1 |
| Franklin County | Zone 1 |
| Fulton County | Zone 2 |
| Gallia County | Zone 2 |
| Geauga County | Zone 2 |
| Greene County | Zone 1 |
| Guernsey County | Zone 1 |
| Hamilton County | Zone 1 |
| Hancock County | Zone 1 |
| Hardin County | Zone 1 |
| Harrison County | Zone 1 |
| Henry County | Zone 2 |
| Highland County | Zone 2 |
| Hocking County | Zone 2 |
| Holmes County | Zone 1 |
| Huron County | Zone 1 |
| Jackson County | Zone 2 |
| Jefferson County | Zone 1 |
| Knox County | Zone 1 |
| Lake County | Zone 2 |
| Lawrence County | Zone 2 |
| Licking County | Zone 1 |
| Logan County | Zone 1 |
| Lorain County | Zone 2 |
| Lucas County | Zone 2 |
| Madison County | Zone 1 |
| Mahoning County | Zone 2 |
| Marion County | Zone 1 |
| Medina County | Zone 2 |
| Meigs County | Zone 2 |
| Mercer County | Zone 1 |
| Miami County | Zone 1 |
| Monroe County | Zone 2 |
| Montgomery County | Zone 1 |
| Morgan County | Zone 2 |
| Morrow County | Zone 1 |
| Muskingum County | Zone 1 |
| Noble County | Zone 2 |
| Ottawa County | Zone 2 |
| Paulding County | Zone 2 |
| Perry County | Zone 1 |
| Pickaway County | Zone 1 |
| Pike County | Zone 1 |
| Portage County | Zone 2 |
| Preble County | Zone 1 |
| Putnam County | Zone 2 |
| Richland County | Zone 1 |
| Ross County | Zone 1 |
| Sandusky County | Zone 2 |
| Scioto County | Zone 2 |
| Seneca County | Zone 1 |
| Shelby County | Zone 1 |
| Stark County | Zone 1 |
| Summit County | Zone 1 |
| Trumbull County | Zone 2 |
| Tuscarawas County | Zone 1 |
| Union County | Zone 1 |
| Van Wert County | Zone 1 |
| Vinton County | Zone 2 |
| Warren County | Zone 1 |
| Washington County | Zone 2 |
| Wayne County | Zone 1 |
| Williams County | Zone 2 |
| Wood County | Zone 2 |
| Wyandot County | Zone 1 |
County names follow the 2020 Census. Zones from the EPA Map of Radon Zones (text version). Rows marked “zone of” use the zone EPA gave the predecessor or surrounding county.
Next steps: read how to test your home, check a result with the level calculator, or look up a single address by ZIP code.