What radon is and why buyers ask
Radon is a radioactive gas that comes from the ground and can build up inside a house. The EPA’s position is simple: “Testing is the only way to know your level of exposure,” and all homes should be tested regardless of where they are.
That’s why radon comes up in so many Ohio sales. A buyer’s inspector offers a radon test as an add-on, the result arrives a few days into the inspection period, and a high number becomes a repair request or a price negotiation.
The numbers that matter: 4 and 2 pCi/L
Radon is measured in picocuries per liter of air, written pCi/L. The EPA’s guidance on its Ohio radon map:
| Result | EPA guidance |
|---|---|
| 4 pCi/L or higher | Fix the home |
| Between 2 and 4 pCi/L | Consider fixing |
| Below 2 pCi/L | No action recommended by this guidance |
In a sale, 4 pCi/L is the figure buyers usually point to. A result at or above it often leads to a request that the seller install a mitigation system, pay for one through a credit, or lower the price.
Ohio’s zone map is not a substitute for a test
The EPA’s Map of Radon Zones, developed in 1993, sorts Ohio counties by predicted average indoor radon: Zone 1 above 4 pCi/L, Zone 2 between 2 and 4, Zone 3 below 2. The map itself warns that it “should not be used to determine if individual homes need to be tested.” The EPA also points readers to a U.S. Geological Survey assessment showing radon potential varies within counties.
So a house in a lower-zone county can test high, and a neighbor’s result tells you little about your own basement. Only a test of your house counts.
What you must disclose as an Ohio seller
Ohio’s disclosure law requires most sellers of residential property to complete the state form under R.C. 5302.30, and the form asks about hazardous materials including radon. The standard is your actual knowledge, given in good faith.
What that means in practice:
- You tested and it was high: disclose it, along with any later result after a fix.
- You have a mitigation system: disclose it. The fan, pipe and label in the basement are visible anyway.
- A previous buyer’s test came back high and that deal fell through: you now know, so disclose it.
- You’ve never tested: say you have no knowledge. You don’t need to test to fill out the form.
The law protects a seller from liability for errors that weren’t within their actual knowledge, but not for hiding what they did know. Our guide to the Ohio residential property disclosure form covers who is exempt from the form.
When the buyer tests
In an Ohio sale, the radon test is often ordered by the buyer during the inspection period in the purchase agreement. To keep the result fair:
- Keep the house closed as the tester instructs: windows shut and doors used only for normal entry.
- Don’t move, cover or unplug the test device, and keep pets and children away from it.
- Keep any existing mitigation fan running.
- Ask for a copy of the report whatever the result.
If the result is high, you can negotiate a credit, agree to install a system before closing, or ask for a retest if the test conditions were questionable.
Your options after a high result
A high radon number is one of the more fixable inspection findings, and the response is a negotiation, not a verdict. The usual choices:
| Option | How it works | Watch out for |
|---|---|---|
| Install a system before closing | You hire a credentialed contractor and give the buyer the post-installation test | Closing can slip if the contractor is booked |
| Give a credit at closing | The buyer installs their own system after closing | Agree the amount in writing, using a written quote |
| Lower the price | Same as a credit, built into the price | The buyer’s lender must agree to the new figure |
| Ask for a retest | Useful if the house wasn’t kept closed or the device was disturbed | It adds days to the inspection period |
| Decline | The buyer can usually walk away under the inspection clause | You now know the result and must disclose it to the next buyer |
Get every change in a signed amendment to the purchase agreement. A verbal promise to “take care of the radon” causes disputes at closing.
Finding a credentialed tester or mitigation contractor
Ohio’s radon program is run by the Ohio Department of Health’s Radon Education and Licensing Program. The EPA lists its contacts as indoor.radon@odh.ohio.gov and 614-644-3020.
The EPA says states that receive federal radon grants provide lists of only those service providers who are credentialed, either through a state process such as a license, or through one of two national programs: the National Radon Proficiency Program or the National Radon Safety Board. Before hiring anyone to test or mitigate, ask for their Ohio credential and check it with ODH.
Testing before you list
Testing before you list is optional, but it can save a deal. A seller who already knows the number can install a system on their own schedule, with their own contractor, instead of under a buyer’s deadline. The trade-off is that a high result becomes something you must disclose.
If you’re selling as-is and don’t want to deal with testing or mitigation, our page on selling a house as-is in Ohio explains what that means, and selling a house that failed inspection covers a deal that fell apart over a report. You can also ask us for a written offer and mention any test results you have.
