Buying & Selling · 9 min read
Radon During Home Sales
How radon fits into a real estate transaction: who tests, how the timeline works, how elevated results are negotiated, and what documentation to keep.
Radon shows up in real estate transactions more often each year, driven partly by buyers relocating from states where testing is routine. It rarely derails a deal, but it does surprise people who have never encountered it.
The main sources of friction are timing and documentation, both of which are manageable with a little planning.
The timeline
Testing happens during the inspection contingency period, which is often 7 to 17 days. A 48-hour continuous monitor test fits comfortably inside that window if it is scheduled early rather than on day nine.
Delays usually come from coordination: getting access, ensuring the home stays closed, and avoiding showings that break the conditions.
Who orders and pays
Most often the buyer, as part of due diligence. Some sellers test before listing to control the timeline and avoid a late surprise, which is increasingly common on higher-value properties.
Either way the protocol is identical, and a pre-listing test does not remove a buyer's right to verify with their own test.
If the result is elevated
Elevated radon becomes an inspection negotiation item, and the usual outcomes are predictable.
- The seller installs a mitigation system before closing, with a post-mitigation test.
- The seller credits the buyer at closing to install a system afterward.
- The price is adjusted to reflect the cost of the work.
- The parties agree to escrow funds pending completion.
Protecting test validity
The single most common problem is a home that was opened up during the test. Sliders left open for a showing, a cleaning crew airing out the house, or a contractor propping the front door will all depress the result.
Signage on exterior doors, written instructions to the listing agent, and a tamper-aware monitor are the standard defenses. A monitor that logs the interruption at least makes the invalidity visible rather than hidden.
Existing mitigation systems
When a listing already has a system, ask for three things: the installation documentation, the post-mitigation test result, and any subsequent tests. Then test anyway during the inspection period.
A running fan proves mechanical operation, not indoor concentration. A short verification test costs little and confirms the system is doing what the seller believes it is doing.
Documentation to keep
After closing, keep the test reports, installation records, fan model and installation date, and the post-mitigation result. These become part of the property file.
That paperwork is genuinely valuable at the next sale, when the same questions will be asked and a documented history removes uncertainty from the negotiation.
Key takeaways
- Test early in the contingency period, not at the deadline.
- Use a tamper-aware continuous monitor for transaction testing.
- Elevated results are a normal, bounded negotiation item.
- Always verify an existing system rather than trusting its presence.