Updated November 2026 · Sources
Radon tests are a routine part of many home sales. The U.S. EPA’s advice is simple: sellers should test now and fix a problem before listing, and buyers should ask whether the home was tested and whether high levels were reduced.
If you are selling
- Test before you list and keep the results; fix a high level so it does not complicate the sale (EPA).
- Buyers often want a test by someone who is not involved in the sale, so consider hiring a certified tester.
- If you already have a mitigation system, keep the installation records and a recent post-mitigation test.
If you are buying
- Ask whether the home has been tested, what the result was and whether a high level was fixed.
- Ask for a test in the areas you plan to use, such as a basement you plan to finish (EPA).
- For a quick decision, the EPA says two short-term tests placed side by side (four inches apart) can be used.
- Ask whether a new home was built with radon-resistant features, and test after you move in anyway.
State radon disclosure rules (examples)
Rules differ by state. Some examples from our state pages:
| State | Rule |
|---|---|
| Illinois | Radon Awareness Act: buyers receive IEMA’s radon pamphlet, and the parties sign a Disclosure of Information on Radon Hazards |
| New Hampshire | Sellers must give buyers a statement about radon, testing and mitigation before a contract (RSA 477:4-a) |
| Montana | Radon warning statement and disclosure of known radon test results to buyers |
| Ohio | Residential property disclosure form covers radon (ORC 5302.30) |
| Wisconsin | Real estate condition report includes radon (Wis. Stat. 709) |
| South Dakota | Seller disclosure of known hazards, including radon (SDCL 43-4-37 to 44) |
| Oklahoma | Disclosure form asks about known radon or radon testing |
| Mississippi | Property Condition Disclosure Statement includes radon gas |
| Colorado | Seller’s Property Disclosure asks about known radon |
Who pays for mitigation?
It is negotiated between buyer and seller. Knowing typical costs helps: published estimates are about $800 to $3,000, and the median reported cost in Pennsylvania was $1,445 in 2026. See our radon mitigation cost guide.
Frequently asked questions
Should I buy a house with high radon?
High radon can be fixed. Most homes can be reduced to 2 pCi/L or below (EPA). Ask the seller to fix it or negotiate the cost, and retest after the system is installed.
Does a radon mitigation system hurt resale value?
A working system with a recent low test result shows the problem was handled, which many buyers want to see.
How long does a radon test take during a home sale?
Most home-sale tests are short-term tests of 2 to 7 days, often with a continuous monitor, so results come back within the inspection period.