Ohio Radon Zone Map
Counties colored by EPA radon zone. Red = Zone 1, Orange = Zone 2, Green = Zone 3.
Highest-Risk Counties
AdamsZone 1 — High
Allen44.4% above action level
Ashland62.5% above action level
Auglaize66.7% above action level
Belmont70% above action level
Butler46.4% above action level
CarrollZone 1 — High
Champaign50% above action level
Clark46.2% above action level
ClintonZone 1 — High
Columbiana63.2% above action level
Coshocton57.1% above action level
+41 more
All 88 Counties — By Radon Risk
| County | EPA Zone | Tests | % Above 4 pCi/L |
|---|
| Adams |
High |
5 |
— |
| Allen |
High |
18 |
44.4% |
| Ashland |
High |
8 |
62.5% |
| Auglaize |
High |
9 |
66.7% |
| Belmont |
High |
10 |
70% |
| Butler |
High |
56 |
46.4% |
| Carroll |
High |
4 |
— |
| Champaign |
High |
8 |
50% |
| Clark |
High |
26 |
46.2% |
| Clinton |
High |
8 |
— |
| Columbiana |
High |
19 |
63.2% |
| Coshocton |
High |
7 |
57.1% |
| Crawford |
High |
9 |
66.7% |
| Darke |
High |
9 |
— |
| Delaware |
High |
26 |
38.5% |
| Fairfield |
High |
26 |
38.5% |
| Fayette |
High |
5 |
— |
| Franklin |
High |
186 |
35.5% |
| Greene |
High |
28 |
35.7% |
| Guernsey |
High |
7 |
57.1% |
| Hamilton |
High |
149 |
34.2% |
| Hancock |
High |
12 |
50% |
| Hardin |
High |
5 |
— |
| Harrison |
High |
4 |
— |
| Holmes |
High |
4 |
— |
| Huron |
High |
10 |
60% |
| Jefferson |
High |
17 |
35.3% |
| Knox |
High |
14 |
50% |
| Licking |
High |
26 |
46.2% |
| Logan |
High |
6 |
— |
| Madison |
High |
8 |
— |
| Marion |
High |
11 |
45.5% |
| Mercer |
High |
9 |
— |
| Miami |
High |
22 |
36.4% |
| Montgomery |
High |
95 |
44.2% |
| Morrow |
High |
6 |
— |
| Muskingum |
High |
15 |
66.7% |
| Perry |
High |
6 |
66.7% |
| Pickaway |
High |
11 |
36.4% |
| Pike |
High |
6 |
— |
| Preble |
High |
8 |
— |
| Richland |
High |
23 |
47.8% |
| Ross |
High |
19 |
36.8% |
| Seneca |
High |
11 |
36.4% |
| Shelby |
High |
8 |
50% |
| Stark |
High |
70 |
41.4% |
| Summit |
High |
105 |
32.4% |
| Tuscarawas |
High |
17 |
41.2% |
| Union |
High |
6 |
66.7% |
| Van Wert |
High |
6 |
— |
| Warren |
High |
37 |
29.7% |
| Wayne |
High |
19 |
42.1% |
| Wyandot |
High |
5 |
— |
| Ashtabula |
Moderate |
21 |
42.9% |
| Athens |
Moderate |
7 |
57.1% |
| Brown |
Moderate |
9 |
44.4% |
| Clermont |
Moderate |
34 |
50% |
| Cuyahoga |
Moderate |
252 |
32.9% |
| Defiance |
Moderate |
4 |
— |
| Erie |
Moderate |
14 |
42.9% |
| Fulton |
Moderate |
9 |
44.4% |
| Gallia |
Moderate |
6 |
66.7% |
| Geauga |
Moderate |
18 |
33.3% |
| Henry |
Moderate |
5 |
— |
| Highland |
Moderate |
7 |
57.1% |
| Hocking |
Moderate |
4 |
— |
| Jackson |
Moderate |
7 |
57.1% |
| Lake |
Moderate |
46 |
37% |
| Lawrence |
Moderate |
13 |
53.8% |
| Lorain |
Moderate |
55 |
47.3% |
| Lucas |
Moderate |
85 |
37.6% |
| Mahoning |
Moderate |
45 |
46.7% |
| Medina |
Moderate |
28 |
57.1% |
| Meigs |
Moderate |
5 |
— |
| Monroe |
Moderate |
4 |
— |
| Morgan |
Moderate |
— |
— |
| Noble |
Moderate |
— |
— |
| Ottawa |
Moderate |
9 |
44.4% |
| Paulding |
Moderate |
5 |
— |
| Portage |
Moderate |
28 |
39.3% |
| Putnam |
Moderate |
4 |
— |
| Sandusky |
Moderate |
12 |
33.3% |
| Scioto |
Moderate |
12 |
50% |
| Trumbull |
Moderate |
44 |
43.2% |
| Vinton |
Moderate |
— |
— |
| Washington |
Moderate |
15 |
40% |
| Williams |
Moderate |
8 |
62.5% |
| Wood |
Moderate |
22 |
36.4% |
Sources: EPA Map of Radon Zones, CDC Environmental Health Tracking Network
Frequently Asked Questions
How many counties in Ohio have high radon risk?
Ohio has 53 counties classified as EPA Zone 1 (high radon risk), 35 as Zone 2 (moderate), and 0 as Zone 3 (low risk).
Is radon a problem in Ohio?
Ohio has 53 high-risk counties where elevated radon is likely. The EPA recommends all homes in Ohio be tested for radon, regardless of which zone they're in.
How do I check radon levels for my Ohio address?
Enter your ZIP code in the search box above to see your county's EPA radon zone and available testing data. For your specific home's radon level, you'll need a radon test kit.