Do You Need a Radon Test to Sell Your House?

Short answer: there is no federal law that requires a radon test to sell a home. But that is not the whole story. Many states have radon disclosure requirements for sellers, buyers routinely ask for radon testing during inspection, and a surprise result mid-transaction is one of the more common ways a closing gets delayed. Here is how it actually plays out.

What federal law says

Federal law does not require radon testing or mitigation in a residential sale. The EPA recommends that all homes be tested and that homes at or above 4.0 pCi/L be mitigated, but that is guidance, not a mandate. The one federal disclosure rule that does exist in real estate covers lead-based paint, not radon.

What states require

State rules generally fall into three buckets:

• Disclosure states. Many states require sellers to disclose known radon test results or known radon hazards on the property, usually through the standard seller disclosure form. Disclosure means telling the buyer what you know. It does not require you to test, and it does not require you to fix anything.
• Awareness states. Some states go a step further and require sellers to give buyers a state radon pamphlet or a specific written notice. Illinois, for example, requires sellers of most residential properties to provide the buyer with the state radon hazard pamphlet and a disclosure document under the Illinois Radon Awareness Act. Minnesota requires sellers to disclose radon test records and mitigation details and to provide a radon warning statement before the purchase agreement is signed under the Minnesota Radon Awareness Act.
• No specific radon rule. In the remaining states, radon falls under general disclosure principles: if you know about a material defect, do not hide it.

The practical rule in every state is the same: never conceal a known result. If your home tested high five years ago and you never mitigated, that result is part of the house's history.

Why buyers usually force the issue anyway

Even where no law requires it, radon testing has become a standard checkbox in home inspections across much of the country, especially in high-radon regions of the Midwest, Mountain West, and Northeast. A buyer's inspector places a 48-hour test during the inspection window, and if the number comes back at or above 4.0 pCi/L, the buyer typically asks the seller to install a mitigation system or credit the cost at closing.

Why testing before you list is usually the smart move

• You control the timeline. A test you run before listing happens on your schedule. A test that happens during the buyer's inspection window happens on theirs, with a closing date on the line.
• Mitigation is cheaper when you are not negotiating under pressure. A radon system installed on your terms, with time to get competing quotes from licensed contractors, tends to cost less than a concession negotiated mid-transaction.
• A good result is a selling point. A recent test below the action level, or an existing mitigation system with a passing retest, removes an objection before it is raised.

If your home already has a mitigation system

Have the paperwork ready: the installation record, the most recent test result, and the fan's age if you know it. Buyers and inspectors will check the manometer (the U-tube pressure gauge on the pipe) to confirm the system is running. A system with no suction reads as a broken system, so it is worth a quick check before showings. See our guide on radon fan replacement for the warning signs.

Bottom line

No state makes you test to sell, but disclosure rules mean you cannot bury a bad result, and buyer-side testing means the question usually comes up anyway. Testing before listing costs little, keeps you in control, and turns radon from a mid-transaction surprise into a line item you have already handled. If you do need a system installed, start with a licensed or certified contractor in your state, and check your state's specific disclosure rules on its page in our directory.