Radon levels in Ohio: Moderate
The model predicts a population-weighted basement average of 2.8 pCi/L across Ohio's 88 counties - about 1.6× the US average of 1.8 pCi/L. Above-ground floors average 1.6 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
53 / 88
EPA Zone 1 counties (60%)
35 / 0
Zone 2 / Zone 3 counties
14
counties predicted ≥ 4 pCi/L
10.7%
of ZIP codes predicted ≥ 4 pCi/L
Ohio counties by predicted radon
Sorted highest to lowest predicted basement average. 88 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Knox County | 5.8 pCi/L | 2.9 | High | EPA Zone 1 | 7 |
| Licking County | 5.8 pCi/L | 3.2 | High | EPA Zone 1 | 11 |
| Champaign County | 4.9 pCi/L | 2.5 | High | EPA Zone 1 | 7 |
| Logan County | 4.5 pCi/L | 2.4 | High | EPA Zone 1 | 12 |
| Fairfield County | 4.5 pCi/L | 2.2 | High | EPA Zone 1 | 14 |
| Ross County | 4.4 pCi/L | 2.4 | High | EPA Zone 1 | 7 |
| Franklin County | 4.3 pCi/L | 2.1 | High | EPA Zone 1 | 38 |
| Madison County | 4.2 pCi/L | 2.4 | High | EPA Zone 1 | 6 |
| Coshocton County | 4.2 pCi/L | 2.2 | High | EPA Zone 1 | 7 |
| Marion County | 4.2 pCi/L | 2.5 | High | EPA Zone 1 | 7 |
| Morrow County | 4.2 pCi/L | 2.3 | High | EPA Zone 1 | 7 |
| Crawford County | 4.1 pCi/L | 2.4 | High | EPA Zone 1 | 4 |
| Delaware County | 4.1 pCi/L | 2.4 | High | EPA Zone 1 | 9 |
| Richland County | 4.0 pCi/L | 2.4 | High | EPA Zone 1 | 11 |
| Tuscarawas County | 4.0 pCi/L | 2.3 | Moderate | EPA Zone 1 | 12 |
| Pickaway County | 3.9 pCi/L | 2.2 | Moderate | EPA Zone 1 | 7 |
| Holmes County | 3.9 pCi/L | 2.3 | Moderate | EPA Zone 1 | 10 |
| Darke County | 3.9 pCi/L | 2.2 | Moderate | EPA Zone 1 | 11 |
| Clark County | 3.8 pCi/L | 2.0 | Moderate | EPA Zone 1 | 11 |
| Miami County | 3.8 pCi/L | 2.2 | Moderate | EPA Zone 1 | 10 |
| Union County | 3.7 pCi/L | 2.0 | Moderate | EPA Zone 1 | 5 |
| Greene County | 3.7 pCi/L | 2.3 | Moderate | EPA Zone 1 | 14 |
| Auglaize County | 3.7 pCi/L | 2.2 | Moderate | EPA Zone 1 | 7 |
| Muskingum County | 3.6 pCi/L | 1.8 | Moderate | EPA Zone 1 | 14 |
| Shelby County | 3.6 pCi/L | 2.0 | Moderate | EPA Zone 1 | 8 |
| Fayette County | 3.6 pCi/L | 2.4 | Moderate | EPA Zone 1 | 3 |
| Guernsey County | 3.6 pCi/L | 2.0 | Moderate | EPA Zone 1 | 8 |
| Wyandot County | 3.5 pCi/L | 2.2 | Moderate | EPA Zone 1 | 6 |
| Huron County | 3.5 pCi/L | 2.0 | Moderate | EPA Zone 1 | 10 |
| Ashland County | 3.5 pCi/L | 2.3 | Moderate | EPA Zone 1 | 7 |
| Harrison County | 3.5 pCi/L | 1.9 | Moderate | EPA Zone 1 | 6 |
| Preble County | 3.5 pCi/L | 2.1 | Moderate | EPA Zone 1 | 8 |
| Perry County | 3.5 pCi/L | 2.0 | Moderate | EPA Zone 1 | 10 |
| Hardin County | 3.4 pCi/L | 2.0 | Moderate | EPA Zone 1 | 8 |
| Wayne County | 3.4 pCi/L | 2.1 | Moderate | EPA Zone 1 | 13 |
| Carroll County | 3.3 pCi/L | 1.9 | Moderate | EPA Zone 1 | 10 |
| Mercer County | 3.3 pCi/L | 2.1 | Moderate | EPA Zone 1 | 7 |
| Pike County | 3.3 pCi/L | 2.0 | Moderate | EPA Zone 1 | 4 |
| Williams County | 3.2 pCi/L | 1.9 | Moderate | EPA Zone 2 | 8 |
| Clinton County | 3.2 pCi/L | 1.8 | Moderate | EPA Zone 1 | 7 |
| Hocking County | 3.1 pCi/L | 1.9 | Moderate | EPA Zone 2 | 5 |
| Seneca County | 3.1 pCi/L | 2.1 | Moderate | EPA Zone 1 | 10 |
| Adams County | 3.1 pCi/L | 1.7 | Moderate | EPA Zone 1 | 8 |
| Jefferson County | 3.0 pCi/L | 1.9 | Moderate | EPA Zone 1 | 15 |
| Belmont County | 3.0 pCi/L | 1.8 | Moderate | EPA Zone 1 | 13 |
| Allen County | 3.0 pCi/L | 1.9 | Moderate | EPA Zone 1 | 10 |
| Van Wert County | 3.0 pCi/L | 1.8 | Moderate | EPA Zone 1 | 6 |
| Columbiana County | 3.0 pCi/L | 1.7 | Moderate | EPA Zone 1 | 15 |
| Putnam County | 3.0 pCi/L | 1.8 | Moderate | EPA Zone 2 | 7 |
| Henry County | 2.9 pCi/L | 1.7 | Moderate | EPA Zone 2 | 8 |
| Hancock County | 2.9 pCi/L | 2.0 | Moderate | EPA Zone 1 | 10 |
| Montgomery County | 2.8 pCi/L | 1.9 | Moderate | EPA Zone 1 | 28 |
| Highland County | 2.8 pCi/L | 1.7 | Moderate | EPA Zone 2 | 4 |
| Butler County | 2.8 pCi/L | 1.8 | Moderate | EPA Zone 1 | 12 |
| Scioto County | 2.7 pCi/L | 1.6 | Moderate | EPA Zone 2 | 10 |
| Warren County | 2.7 pCi/L | 1.8 | Moderate | EPA Zone 1 | 11 |
| Sandusky County | 2.7 pCi/L | 1.4 | Moderate | EPA Zone 2 | 8 |
| Vinton County | 2.7 pCi/L | 1.6 | Moderate | EPA Zone 2 | 7 |
| Erie County | 2.6 pCi/L | 1.4 | Moderate | EPA Zone 2 | 7 |
| Stark County | 2.6 pCi/L | 1.5 | Moderate | EPA Zone 1 | 27 |
| Morgan County | 2.6 pCi/L | 1.5 | Moderate | EPA Zone 2 | 5 |
| Monroe County | 2.5 pCi/L | 1.4 | Moderate | EPA Zone 2 | 7 |
| Paulding County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 8 |
| Portage County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 13 |
| Jackson County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 4 |
| Noble County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 6 |
| Athens County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 10 |
| Brown County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 8 |
| Gallia County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 6 |
| Meigs County | 2.4 pCi/L | 1.4 | Moderate | EPA Zone 2 | 10 |
| Lawrence County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 9 |
| Medina County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 11 |
| Washington County | 2.3 pCi/L | 1.5 | Moderate | EPA Zone 2 | 14 |
| Summit County | 2.2 pCi/L | 1.2 | Moderate | EPA Zone 1 | 31 |
| Clermont County | 2.2 pCi/L | 1.2 | Moderate | EPA Zone 2 | 12 |
| Geauga County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 10 |
| Defiance County | 2.2 pCi/L | 1.1 | Moderate | EPA Zone 2 | 5 |
| Trumbull County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 23 |
| Fulton County | 2.2 pCi/L | 1.2 | Moderate | EPA Zone 2 | 7 |
| Mahoning County | 2.1 pCi/L | 1.3 | Moderate | EPA Zone 2 | 26 |
| Lorain County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 14 |
| Ashtabula County | 2.1 pCi/L | 1.1 | Moderate | EPA Zone 2 | 14 |
| Ottawa County | 2.0 pCi/L | 1.4 | Moderate | EPA Zone 2 | 7 |
| Lake County | 1.9 pCi/L | 1.1 | Low | EPA Zone 2 | 7 |
| Wood County | 1.8 pCi/L | 1.4 | Low | EPA Zone 2 | 21 |
| Hamilton County | 1.8 pCi/L | 1.1 | Low | EPA Zone 1 | 51 |
| Cuyahoga County | 1.7 pCi/L | 1.0 | Low | EPA Zone 2 | 51 |
| Lucas County | 1.2 pCi/L | 0.9 | Low | EPA Zone 2 | 24 |
Ohio radon questions
- Is radon high in Ohio?
- Ohio's population-weighted predicted basement average is 2.8 pCi/L, about 1.6× the US average of 1.8. 14 of its 88 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 69 are in the 2-4 "consider fixing" range and 5 are below 2. 10.7% of Ohio ZIP codes are predicted at 4 or higher.
- Which Ohio county has the highest radon?
- Knox County has the highest predicted basement average in Ohio at 5.8 pCi/L (EPA Zone 1). The lowest is Lucas County at 1.2 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Ohio?
- 53 of Ohio's 88 counties (60%) are EPA Zone 1 (highest potential), 35 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Ohio?
- Yes - with some urgency. Ohio's predicted average is in the moderate range, and 82.8% of its ZIP codes are predicted at 2 pCi/L or higher. A short-term charcoal kit or a continuous digital monitor will tell you your actual level within days.
Ohio radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Ohio radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.