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Last reviewed 2026-10-20

Radon in Ohio: County Levels, Licensing and Cost

Across 525,229 pre-mitigation radon tests in the Ohio Department of Health's county dashboard, 34.4% read at or above EPA's 4 pCi/L action level, by our test-weighted count of ODH's county file (2010 to present, retrieved October 16, 2026). EPA estimates about 1 in 15 homes nationally are elevated (EPA Citizen's Guide, 2016).

EPA's 1993 Map of Radon Zones places 53 of Ohio's 88 counties in Zone 1. A typical sub-slab system costs $1,200 to $2,000 installed nationally (HomeGuide, Feb 2026), and in Ohio the mitigation specialist and contractor must be licensed by ODH under Ohio Administrative Code Chapter 3701-69.

Ohio publishes county data rather than ZIP-level results, so the radon levels by ZIP tool shows each Ohio ZIP's county result from ODH plus its EPA zone, and says so on the page.

Licensing and permits

Licensing: ODH licenses radon testers, mitigation specialists and contractors under Ohio Administrative Code Chapter 3701-69 (for example, OAC 3701-69-04). Applicants complete approved measurement and mitigation training and pass exams. ODH publishes a daily-updated licensee data set on data.ohio.gov.

Check the license: search the Ohio radon licensure data set for the installer's name before signing, and ask for the post-mitigation test result in writing.

Local permits: some Ohio municipalities require an electrical or building permit for the fan circuit. HomeGuide reports radon permits at $25 to $150 nationally, usually included in the bid.

Home sales: a radon test during the inspection period should be done by an ODH-licensed tester.

Local conditions

Central Ohio carries the highest county shares in ODH data: Pickaway (52.99% of 1,472 tests at or above 4 pCi/L), Fairfield (52.89% of 7,580), Madison (52.59% of 1,234), Coshocton (52.03% of 246), Morrow (51.60% of 721) and Licking (51.08% of 11,407).

The biggest test counts come from the metros: Franklin County (Columbus) logged 114,203 tests with 44.88% at or above 4 pCi/L, while Cuyahoga (Cleveland) logged 50,216 at 15.41% and Hamilton (Cincinnati) 44,070 at 21.36% (ODH).

Northeast and southwest Ohio test lower but not low: Summit County (Akron) logged 31,984 tests with 28.24% at or above 4 pCi/L, and Montgomery County (Dayton) 28,889 tests at 32.82% (ODH). Those shares are still several times EPA's national estimate of about 1 in 15 homes (EPA Citizen's Guide, 2016).

County geometric means in the ODH file run from 0.9 to 5.06 pCi/L. Pickaway County's 4.79 pCi/L geometric mean is above the action level on its own.

Glaciers covered roughly the western and northern two-thirds of Ohio, leaving till and outwash sand and gravel over the bedrock; the unglaciated hills of southeast Ohio along the Ohio River sit directly on sandstone and shale. Homes on the till plains north and west of Columbus mostly have full basements, while houses in the hill country along the river valleys more often stand on crawlspaces or slabs, which changes the system a mitigator designs.

Geology explains much of the central Ohio pattern: the Ohio Department of Natural Resources Geological Survey ties high indoor radon to Wisconsinan glacial till that carried uranium-rich Ohio Shale fragments, and to permeable sand and gravel that lets soil gas move easily (Ohio DNR Geological Survey; Ohio State Report of Investigations 144).

What drives local prices

Foundation across Ohio's counties: basement, slab, crawlspace or a combination (EPA Consumer's Guide). A sub-slab system runs $1,200 to $2,000 and a crawlspace membrane $1,000 to $2,500 (EPA, 2010 dollars), based on the published ranges.
Suction points needed: depends on sub-slab gravel and soil (EPA Consumer's Guide); our calculator adds an est. $250 to $500 per extra point.
Pipe route and fan location: interior or attic routes are an est. ×1.15.
Permit and retest: $25 to $150 for a local permit where required and $125 to $400 for a professional retest (HomeGuide).
Licensed-contractor requirement under OAC 3701-69 (est. cost effect).
Starting radon level: central Ohio counties with geometric means above 4 pCi/L in ODH data may need stronger systems (est.).

Common jobs

Sub-slab depressurization, basement or slab home: $1,200 to $2,000 installed nationally (HomeGuide, Feb 2026).
Crawlspace submembrane depressurization: $1,000 to $2,500 in EPA's 2010 Consumer's Guide (2010 dollars).
Sump pit sealing and cover as part of a system: $900 to $2,500 (HomeGuide).
Post-mitigation test: HomeGuide lists $125 to $400 for a professional test or $10 to $30 for a kit.

From test to fixed, and where we cover

Our first Ohio county page covers Delaware County, north of Columbus, where 49.64% of 23,086 tests in the ODH dashboard read 4 pCi/L or higher. The quote form routes Ohio requests to ODH-licensed mitigation contractors only.

Ohio's data is county-level, so the ZIP tool labels every Ohio result "county figure (ODH)" and adds the EPA zone of the county covering most of the ZIP. Where a ZIP crosses into a second county (common around Columbus, where Franklin, Delaware, Licking and Fairfield meet), the tool lists each county and its figure.

Step 1: test with a kit or an ODH-licensed tester. Step 2: at 4 pCi/L or higher, get two bids from ODH-licensed mitigation contractors. Step 3: check the licensure data set and compare bids with the calculator. Step 4: retest after the system has run at least 24 hours (EPA Consumer's Guide).

Communities: Columbus, Lancaster, Circleville, Newark, London, Mount Gilead, Coshocton, Dayton, Cleveland, Cincinnati

Questions about Ohio

How common is high radon in Ohio?

34.4% of 525,229 tests in the ODH county dashboard read 4 pCi/L or higher (our test-weighted count, 2010 to present).

Which Ohio counties have the highest radon?

Pickaway, Fairfield, Madison, Coshocton, Morrow and Licking each had more than 51% of tests at or above 4 pCi/L in ODH data.

Does Ohio license radon mitigators?

Yes. ODH licenses testers, mitigation specialists and contractors under Ohio Administrative Code Chapter 3701-69.

Does Ohio publish radon by ZIP code?

ODH publishes county results. Our ZIP tool shows the county figure for each Ohio ZIP and the EPA zone, and labels it as county data.

How much does radon mitigation cost in Ohio?

No state agency publishes prices. National survey data puts a standard system at $1,200 to $2,000 (HomeGuide, Feb 2026). Use the calculator and get two ODH-licensed bids.

Is radon worse in central Ohio?

In ODH's county data, yes. Franklin County's 114,203 tests showed 44.88% at or above 4 pCi/L, and neighboring Fairfield, Licking, Pickaway and Madison counties were all above 51%.

Sources

County radon guides in Ohio

Rules and fees change; confirm with the state radon office. Price your own system with the radon mitigation cost calculator, read the radon mitigation cost guide, or check any ZIP with the radon levels by ZIP tool.