Radon levels in Ohio: Moderate
The model predicts a population-weighted basement average of 2.8 pCi/L (model estimate) 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
Test Ohio - the EPA says "consider fixing" in this range
The predicted basement average here is 2.8 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Monitor link goes to the Airthings store - use code RADONGRADE-10OFF at checkout for 10% off any Airthings monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
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What the data says about radon in Ohio
On the EPA's 1993 radon zone map, 53 of Ohio's 88 counties are EPA Zone 1 (60%), 35 are Zone 2 and 0 are Zone 3. Zone 1 - the highest-potential class, predicted screening average above 4 pCi/L - is the most common designation in Ohio. That classification has not been revised since 1993; it describes counties, not homes, and elevated readings turn up in Zone 3 counties every year.
Ohio models out at 2.8 pCi/L predicted basement average (moderate; 1.6× the US population-weighted average of 1.8). Of the 88 counties with predictions, 14 are predicted at or above 4 pCi/L, 69 in the 2-4 band and 5 below 2. The highest predicted county is Knox County at 5.8 pCi/L; the lowest is Lucas County at 1.2 - a 4.6 pCi/L spread that means a statewide average tells you little about any one county.
At ZIP-code resolution, 10.7% of Ohio ZIPs are predicted at 4 pCi/L or higher in the basement and 82.8% at 2 or higher - above the national shares of 4.2% and 48.7%. With more than half of ZIPs above 2, a test is worth doing before any purchase or renovation here.
Ohio counties by predicted radon
Sorted highest to lowest predicted basement average (model estimate). 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 |
Radon levels in Ohio cities
The 27 most-populous Ohio places among the 1,000 largest US cities (Census incorporated places and CDPs), by population. City figures are ZIP-land-weighted means of the model's ZIP predictions (model estimate).
| City | Population | Predicted basement | Upstairs | Grade | ZIPs ≥ 4 |
|---|---|---|---|---|---|
| Columbus | 913,175 | 4.3 pCi/L | 2.0 | High | 54% |
| Cleveland | 362,656 | 1.3 pCi/L | 0.8 | Low | 0% |
| Cincinnati | 311,097 | 1.6 pCi/L | 0.9 | Low | 0% |
| Toledo | 265,304 | 1.1 pCi/L | 0.8 | Low | 0% |
| Akron | 188,701 | 2.0 pCi/L | 1.1 | Low | 0% |
| Dayton | 135,512 | 2.9 pCi/L | 1.8 | Moderate | 0% |
| Parma | 78,951 | 1.8 pCi/L | 1.1 | Low | 0% |
| Canton | 69,197 | 2.5 pCi/L | 1.5 | Moderate | 0% |
| Lorain | 65,337 | 1.7 pCi/L | 1.0 | Low | 0% |
| Hamilton | 62,997 | 2.7 pCi/L | 1.8 | Moderate | 0% |
| Youngstown | 59,108 | 2.0 pCi/L | 1.1 | Low | 0% |
| Springfield | 58,082 | 3.6 pCi/L | 1.9 | Moderate | 40% |
| Kettering | 56,876 | 2.8 pCi/L | 2.0 | Moderate | 0% |
| Elyria | 53,117 | 2.0 pCi/L | 1.2 | Low | 0% |
| Middletown | 51,478 | 2.9 pCi/L | 1.9 | Moderate | 0% |
| Newark | 51,046 | 7.5 pCi/L | 3.8 | High | 100% |
| Cuyahoga Falls | 50,742 | 2.2 pCi/L | 1.2 | Moderate | 0% |
| Lakewood | 49,337 | 1.2 pCi/L | 0.7 | Low | 0% |
| Dublin | 48,923 | 4.2 pCi/L | 2.3 | High | 50% |
| Euclid | 48,212 | 1.3 pCi/L | 0.8 | Low | 0% |
| Mansfield | 47,711 | 3.9 pCi/L | 2.3 | Moderate | 33% |
| Beavercreek | 47,193 | 3.1 pCi/L | 1.9 | Moderate | 14% |
| Mentor | 46,929 | 2.0 pCi/L | 1.1 | Moderate | 0% |
| Strongsville | 45,511 | 2.1 pCi/L | 1.3 | Moderate | 0% |
| Delaware | 45,158 | 4.9 pCi/L | 2.7 | High | 50% |
| Fairfield | 44,447 | 3.1 pCi/L | 1.7 | Moderate | 0% |
| Cleveland Heights | 43,908 | 1.5 pCi/L | 1.1 | Low | 0% |
Highest-radon ZIP codes in Ohio
The 10 Ohio ZIP codes with the highest predicted basement average (model estimate), out of 1,006 modeled. A ZIP average is still an area figure - neighboring homes routinely test several pCi/L apart.
| ZIP | County | Predicted basement | Upstairs | Grade |
|---|---|---|---|---|
| 43055 | Licking County | 7.5 pCi/L | 3.8 | High |
| 43357 | Logan County | 7.3 pCi/L | 3.0 | High |
| 43028 | Knox County | 6.5 pCi/L | 2.3 | High |
| 43050 | Knox County | 6.3 pCi/L | 3.1 | High |
| 43085 | Franklin County | 5.7 pCi/L | 2.7 | High |
| 43056 | Licking County | 5.5 pCi/L | 2.6 | High |
| 43080 | Licking County | 5.5 pCi/L | 2.7 | High |
| 43078 | Champaign County | 5.5 pCi/L | 2.7 | High |
| 43220 | Franklin County | 5.4 pCi/L | 2.2 | High |
| 43110 | Fairfield County | 5.3 pCi/L | 2.2 | High |
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 area figures; 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
Ohio's radon program page is at odh.ohio.gov; it lists testing and certified-mitigator guidance for the state. The EPA also keeps a directory of every state radon contact: EPA state radon contacts page. Then read how to test and what mitigation costs.