Radon when buying or selling a home in Ohio

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General information only. This page summarizes public guidance from EPA, the Ohio Department of Health and Ohio law. It is not professional radon, legal or medical advice. For questions about a specific home, contact ODH radon education staff (614-728-0272, [email protected]) or an Ohio-licensed radon professional (ODH). For contract questions, ask your real estate agent or an attorney.

What the Ohio disclosure form asks

Most Ohio home sellers must give buyers a completed Residential Property Disclosure Form (ORC 5302.30; the form itself is set by Ohio Adm. Code 1301:5-6-10). Its hazardous materials section asks whether the seller knows of the previous or current presence of radon gas, with Yes, No or Unknown answers, the radon level if known, and any repairs, remediation or mitigation (Ohio Residential Property Disclosure Form).

Keep the limits in mind. The law says the form covers what the seller actually knows, isn't a warranty, and isn't a substitute for an inspection, and it encourages buyers to get their own professional inspection (ORC 5302.30). The form tells buyers to do whatever due diligence they think is needed about radon and lists EPA and ODH resources (disclosure form). An "Unknown" or "No" answer can simply mean nobody ever tested.

If you're selling

• EPA recommends testing before you list and, if needed, lowering the level, because fixing it before the house is on the market gives you more time (EPA Home Buyer's and Seller's Guide).
• If you already tested, check that the test followed EPA's testing checklist, then share the results with buyers. Keep your results and any mitigation records (EPA Home Buyer's and Seller's Guide).
• A buyer may still ask for a new test, for example if the last test is more than about two years old, you renovated since, or they plan to use a lower level such as the basement (EPA Home Buyer's and Seller's Guide).
• Test the lowest level that could be used regularly, finished or not, since a buyer may use a space you don't (EPA Home Buyer's and Seller's Guide).

If you're buying

• Ask the seller for past radon results, and for any information on an existing radon system (EPA Home Buyer's and Seller's Guide).
• Before you accept an old result, find out who ran the test, where in the house it was placed, and whether the house has been changed since (EPA Home Buyer's and Seller's Guide).
• If there's no recent valid test, EPA suggests your purchase contract spell out where and when the test happens, who does it, what kind of test it is, how results and costs are shared, and who pays for any mitigation and when (EPA Home Buyer's and Seller's Guide).
• In Ohio, a radon test done for someone else, such as one for a home sale, must be done by an ODH-licensed radon tester. Testing your own home is exempt (Ohio Adm. Code 3701-69-02). ODH's "Hire a Professional" page points to its license lookup (ODH).

EPA's three test options for a sale

When a quick answer is needed, EPA accepts any of these short-term options for deciding whether to fix the home (EPA Home Buyer's and Seller's Guide):

EPA notes the trade-off: side-by-side tests improve precision, while back-to-back tests better reflect the seasonal average. Results near 4 pCi/L are less certain; EPA says an average of 4.1 pCi/L from two short-term tests means about a 50 percent chance the year-round average is somewhat above or below 4 (EPA Home Buyer's and Seller's Guide). What the numbers mean in general: radon levels explained.

Keeping the test honest

EPA says any real estate radon test should include steps to prevent or detect interference, because opening windows or moving the device can skew the result (EPA Home Buyer's and Seller's Guide). Methods EPA lists:

• A device that records radon frequently, so unusual swings show up.
• Motion or proximity detectors, and temperature and barometric pressure logs.
• Tamper-proof seals on windows.
• A non-interference agreement signed by the seller or occupant.

Closed-house conditions mean windows closed and doors closed except for normal coming and going, starting at least 12 hours before a 2 to 4 day test. Run heating and cooling normally. If the house already has a radon system, make sure the fan is working and stays on for the whole test (EPA Home Buyer's and Seller's Guide). More setup details: how to test for radon.

If the result is 4 pCi/L or higher

EPA recommends fixing the home at 4 pCi/L or more, and says the buyer and seller should discuss the timing and cost of the fix. Most homes can be fixed for about the same cost as other common home repairs; get an estimate from one or more qualified mitigators (EPA Home Buyer's and Seller's Guide). In Ohio, mitigation work must be done by an ODH-licensed mitigation contractor (Ohio Adm. Code 3701-69-02). How systems work and how to check a license: radon mitigation in Ohio.

EPA also says sealing cracks alone isn't recommended as the fix, since it hasn't been shown to lower radon significantly or consistently, and that the home should be retested after it's fixed (EPA Home Buyer's and Seller's Guide).

New construction

If you're buying a newly built home, ask whether radon-resistant features were used and whether the home has been tested. EPA says even a radon-resistant home should be tested as soon as possible after move-in, and if it's 4 pCi/L or more, a fan can be added to a passive system (EPA Home Buyer's and Seller's Guide).

Last updated: 2026-10-28