Buying or selling a home in Ohio? Ohio Rev. Code § 5302.30 — the Ohio Residential Property Disclosure Act — requires sellers of most residential property to complete the state-prescribed Residential Property Disclosure Form before contract signing. Section 6 of that form addresses radon specifically. How a seller answers Section 6 affects whether radon becomes a contingency, a closing credit, or a price-reduction conversation. Here's what each side needs to know.
What Ohio Rev. Code § 5302.30 actually requires
The Ohio Residential Property Disclosure Act (Ohio Rev. Code § 5302.30) applies to most sales of residential property with one to four dwelling units. The seller must provide the buyer with a completed Residential Property Disclosure Form before the buyer signs the contract — or, if the buyer signs without it, the buyer has a three-day window to rescind after receiving the form.
Exceptions: the act does NOT apply to transfers between co-owners, between spouses incident to a divorce, by fiduciaries (executors, trustees), in foreclosure or bankruptcy, or as a new construction sale by the original builder. Buyers in these exempt transactions don't get the protection of the disclosure form — making independent radon testing during the inspection period even more important.
Section 6 — Radon-specific language
Section 6 of the Ohio Residential Property Disclosure Form asks the seller several questions about radon:
- Has the property been tested for radon? (Yes / No / Unknown)
- If yes, when was it tested?
- What were the results? (specific pCi/L value if known)
- Has a radon mitigation system been installed? (Yes / No / Unknown)
- If yes, when was it installed and by whom?
Sellers must disclose information they actually have. They are NOT required to test the home before selling. "Unknown" is a valid answer for any question where the seller genuinely doesn't have the information — and is the most common answer because most sellers haven't tested.
What sellers should know
Honesty protects you. Misrepresenting known information on the disclosure form creates legal liability after closing. If you tested years ago and saw elevated levels, disclose it — including the steps you took (or didn't take). Sellers who voluntarily disclose past elevated readings and any remediation work generally come out ahead in negotiations vs sellers who try to hide a history that the buyer's inspector then finds.
Get tested before listing if you want to control the narrative. A short-term radon test (3-7 days) costs ~$15-25 with a do-it-yourself kit or ~$150-250 with a continuous radon monitor. If the test is below 4 pCi/L, you can mark Section 6 with confidence. If it's above 4 pCi/L, you can address it with a professional mitigation system before listing — usually $800-$2,500 — and disclose both the elevated test result AND the corrective action. Buyers love seeing "tested at 8.2 pCi/L on 2026-01-15, mitigation system installed 2026-02-03 by NRPP + ODH-licensed contractor, post-mitigation test 1.4 pCi/L on 2026-02-25" — it's the closure story buyers want.
What buyers should know
Don't rely on "Unknown." Most sellers honestly don't know their home's radon status. "Unknown" doesn't mean the home is safe — it means it hasn't been tested. Ohio's EPA Zone 1 designation across most of the state means there's a real chance any given home tests elevated. Order a radon test as part of your inspection period — typically $150-250 for a 48-hour continuous monitor test, performed by your home inspector or a separate NRPP-certified tester.
If the test comes back elevated (above 4 pCi/L): you have several options. (1) Request the seller install a mitigation system as a condition of closing — usually $800-$2,500. (2) Request a closing credit equal to the mitigation cost and install the system yourself after closing. (3) Walk away if the inspection contingency is still active.
Radon contingency clauses — sample language
If you want to include a specific radon contingency in your purchase offer (recommended in Ohio), ask your agent to use language like:
"This offer is contingent upon a radon test conducted by a licensed Ohio radon professional during the inspection period showing indoor radon levels of 4.0 pCi/L or below. If levels are above 4.0 pCi/L, Seller agrees to either (a) install an ODH-licensed radon mitigation system at Seller's expense before closing, with post-mitigation test confirming levels below 4.0 pCi/L, OR (b) provide Buyer with a closing credit equal to the mitigation system cost. Buyer reserves the right to terminate this contract if these conditions cannot be met."
Bottom line
Ohio Rev. Code § 5302.30 gives buyers a tool — the disclosure form — to learn what sellers know about radon. But the form only captures what sellers DO know. Buyers should independently test during the inspection period regardless of what the disclosure form says. Sellers should consider testing before listing to control the narrative and avoid surprise during inspection. And both sides benefit from understanding that Ohio's elevated-radon profile (driven by glacial till in the north + west and Appalachian Plateau geology in the east + southeast) makes radon a likely transaction issue regardless of property age or condition.