Ohio ranks among the highest-risk states for indoor radon exposure. More than half of Ohio’s counties fall in EPA Zone 1 — the highest-risk classification, where average indoor radon levels are predicted to exceed 4 picocuries per liter (pCi/L). For Ohio homeowners, testing is not optional. It is a basic safety measure.
Ohio Radon Risk: What the Data Shows
The EPA’s radon zone map divides Ohio into three risk tiers:
- Zone 1 (High Risk — >4 pCi/L predicted average): The majority of Ohio counties, including Franklin, Cuyahoga, Hamilton, Summit, and Lucas
- Zone 2 (Moderate Risk — 2–4 pCi/L): Scattered counties in eastern and southern Ohio
- Zone 3 (Low Risk — <2 pCi/L): Very few Ohio counties fall in this category
The Ohio Department of Health reports that radon is the second leading cause of lung cancer in the United States, responsible for approximately 21,000 deaths per year according to the EPA. Ohio’s geology compounds the risk: glacially-deposited soil rich in uranium-bearing minerals is common across northwest and central Ohio. As uranium decays, it produces radium, which produces radon gas. That gas migrates upward through soil and enters homes through foundation cracks, sump pits, and utility penetrations.
Ohio Radon Statistics
- Average indoor radon level in Ohio: 3.5–5.0 pCi/L in tested homes
- EPA action level: 4.0 pCi/L (mitigation recommended at or above this threshold)
- Ohio homes tested: Estimated fewer than 30% of existing housing stock
- Primary geological source: Uranium-rich glacial till covering much of northwest and central Ohio
Ohio Radon Certification Requirements
Ohio requires that radon testing and mitigation professionals hold active national certification. The state aligns with two recognized credentialing bodies:
- NRPP (National Radon Proficiency Program) — the primary recognized certification in Ohio
- NRSB (National Radon Safety Board) — also accepted
Ohio does not operate a separate state licensing board for radon contractors. Before hiring any contractor, confirm their certification number through nrpp.info or nrsb.org and verify that the certification is current.
High-Risk Ohio Counties
While all Ohio homeowners should test, these counties have documented elevated average radon levels based on EPA zone classification and Ohio Department of Health screening data:
| County | EPA Zone | Notable Area |
|---|---|---|
| Franklin | 1 | Columbus metro |
| Cuyahoga | 1 | Cleveland metro |
| Hamilton | 1 | Cincinnati metro |
| Lucas | 1 | Toledo metro |
| Summit | 1 | Akron metro |
| Montgomery | 1 | Dayton metro |
| Stark | 1 | Canton area |
| Delaware | 1 | Columbus suburbs |
| Warren | 1 | Cincinnati suburbs |
| Licking | 1 | Central Ohio |
Testing in these counties is a priority — particularly in homes with basements, crawl spaces, or slab-on-grade foundations built before 1990.
Radon Testing in Ohio: What to Expect
Short-Term Testing (2–7 Days)
Uses a charcoal canister or electret ion chamber placed in the lowest livable area of the home. Best for real estate transactions or initial screening. DIY kits cost $15–$40; professional testing runs $100–$200.
Long-Term Testing (90 Days–1 Year)
Alpha track detectors provide a time-averaged reading that accounts for seasonal variation. More accurate for baseline assessment and post-mitigation confirmation.
EPA Testing Protocol
- Close all windows and doors 12 hours before test start (closed-house conditions)
- Place test device in the lowest livable area of the home (basement preferred)
- At or above 4.0 pCi/L: schedule mitigation
- Between 2.0–4.0 pCi/L: mitigation is worth considering, particularly in Zone 1 counties
Radon Mitigation in Ohio: Methods and Costs
Sub-slab depressurization (ASD) is the standard mitigation method for most Ohio homes. A PVC pipe is installed through the foundation slab or a crawl space wall. A small fan creates negative pressure beneath the slab, drawing radon from the soil and exhausting it above the roofline — away from windows and air intakes.
Typical Ohio Mitigation Costs
- Standard ASD system (single extraction point): $800–$1,400
- Complex installations (multiple entry points, finished basements): $1,500–$2,500
- Post-mitigation re-test: Required; conducted 24–48 hours after system activation
- Annual fan inspection: Recommended; $50–$100
A properly installed system typically reduces indoor radon to below 2.0 pCi/L. The EPA reports that sub-slab depressurization reduces radon levels by an average of 99% when correctly installed.
Ohio Radon Financial Assistance
Ohio does not currently operate a state-funded residential radon mitigation grant program. However, some options exist:
- Ohio Weatherization Assistance Program (WAP): Some WAP contractors hold radon certifications and may address radon as part of an energy audit for eligible households
- HUD-assisted housing: Properties receiving HUD rehabilitation funding may qualify for radon testing and mitigation as part of the project scope
- Tax guidance: No specific federal radon tax credit currently exists; consult a tax professional regarding home improvement deductions
For current state program updates, check the Ohio Department of Health radon page.
Ohio Cities We Serve
Certified radon testing and mitigation services are available across Ohio’s major markets:
- Radon Testing in Columbus, OH
- Radon Testing in Cleveland, OH
- Radon Testing in Cincinnati, OH
- Radon Testing in Toledo, OH
- Radon Testing in Dayton, OH
- Radon Testing in Akron, OH
Frequently Asked Questions: Radon in Ohio
Is Ohio a high-risk state for radon?
Yes. The majority of Ohio counties are in EPA Zone 1, the highest risk classification. Ohio’s glacially-derived soils are rich in uranium-bearing minerals, making elevated radon a widespread issue across the state — not limited to specific regions.
What is the average radon level in Ohio homes?
Tested homes in Ohio commonly measure between 3.5 and 5.0 pCi/L. Many untested homes — particularly those with basements in Zone 1 counties — likely exceed the 4.0 pCi/L EPA action threshold.
Does Ohio require radon testing when selling a home?
Ohio does not mandate radon testing for real estate transactions. However, buyers routinely request it, and real estate professionals in the state commonly recommend it as standard due diligence. Sellers who have tested and mitigated are typically in a stronger negotiating position.
How do I find a certified radon contractor in Ohio?
Search the NRPP contractor directory at nrpp.info or the NRSB directory at nrsb.org. Filter by Ohio and your county. Verify that the contractor’s certification is active before scheduling.
How long does radon mitigation take in Ohio?
A standard sub-slab depressurization system is typically installed in 2–4 hours. The system is operational immediately. A follow-up test is conducted 24–48 hours post-installation to confirm radon levels have dropped to the acceptable range.
What radon level requires mitigation in Ohio?
The EPA recommends mitigation at 4.0 pCi/L or above. At levels between 2.0 and 4.0 pCi/L, mitigation is worth considering — particularly in older homes or homes in Zone 1 counties. There is no radon level below which risk is entirely absent.
Get a Free Radon Test Quote in Ohio
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- U.S. EPA — A Citizen’s Guide to Radon
- EPA Map of Radon Zones — Ohio
- Ohio Department of Health — Radon Program
- NRPP Contractor Directory
- NRSB Contractor Directory
- World Health Organization — Handbook on Indoor Radon (2009)