Radon in a home sale or a rental is mostly a matter of state law and of what your contract says. We found no national radon disclosure law. A standard home inspection doesn’t test for radon, and the FHA, VA and Fannie Mae rules we read don’t require a test to buy a single-family home. So the test won’t happen unless you arrange it. EPA’s Home Buyer’s and Seller’s Guide (March 2024) still says: “If you are buying or selling a home, have it tested for radon.”
The guides below follow the order a sale runs in, then turn to rentals. Rules are as we read them on 4 November 2026. Radon Handbook sells nothing and refers no one. This page is general information, not medical, engineering, legal or financial advice.
Buying: arrange the test yourself
A home inspection is a look at the house, and radon can’t be seen. The written standards of InterNACHI, an inspector association, say the inspector need not determine whether radon is present. Some inspectors sell a test as an extra. If radon isn’t listed in your agreement as a separate test with a result, assume you aren’t getting one.
Time is the usual problem. EPA’s options for a sale all run at least 48 hours, and for tests of two to four days the windows stay closed from 12 hours before the start, so plan on at least 60 hours. Lab results by mail can take “a few days or weeks”, EPA says. Check that against your contract deadline, using how long a radon test takes.
The test belongs on the lowest level that could be used regularly, finished or not, so a basement you plan to use counts. And because someone else lives there, EPA says “any real estate test for radon should include steps to prevent or detect interference with the test device.” Our guide on how to test for radon covers the steps.
What loans actually require
You may hear that “FHA or VA requires a radon test.” The documents we read don’t back that up:
- FHA. A text search of Handbook 4000.1, Update 18, found no mention of radon. The buyer form it requires, HUD-92564-CN, does say that EPA and the Surgeon General “recommend that all houses be tested for radon”.
- VA. VA removed radon from its Chapter 12 property rules (change dated 27 February 2026, in the version effective after 1 May 2026).
- Fannie Mae. The section we read sets no test requirement, though an appraiser who knows of a hazard such as radon gas must note it in the report.
- Freddie Mac and USDA. Not confirmed. We read only part of Freddie Mac’s guide, and USDA’s handbook would not open for us.
Nothing we read stops a lender from adding a condition of its own, and state law or your contract can add more. If someone tells you the loan requires a test, ask to see the rule in writing. Our guide to radon in home inspections and loan rules shows what each text says, and how to add a test to your purchase.
If the house already has a system
A radon system isn’t a defect. It usually means someone tested the house, found a high number and dealt with it. What it can’t tell you is today’s level, so test with the system running throughout.
EPA’s Consumer’s Guide (2025 cover) says the fan “should NEVER be turned off”, and that it “must not be located in or below a livable area.” Check by eye, never by switching anything off, and ask for the results from before and after the install.
Our guide to buying a house with a radon system has the full checklist, running costs and when to push back.
Selling: what you have to say
If a seller knows something about radon in the house, a state rule or form probably requires them to say so. In the laws and forms we read, that duty covers what the seller knows, and none in force today requires a test. Rhode Island is the one to watch: a testing law is reported for most home sales from 1 June 2027, but we couldn’t read its final text, so treat that as reported, not confirmed.
Be careful with the claim that 37 states require disclosure. It traces to a January 2017 summary of laws in effect on 1 December 2016, and it mixes laws, regulations and real estate commission forms. Our state-by-state radon disclosure guide sorts the states by kind of rule and says how far we read each one.
Details differ. Colorado, Minnesota and North Dakota say “any knowledge”, so a result under 4 picocuries per liter of air (pCi/L, the US unit for radon) can count there too. In Minnesota a seller who knows material facts and fails to disclose is liable to the buyer, who has two years from closing to sue.
EPA’s advice goes further than any of these laws: “EPA recommends that you test your home before putting it on the market and, if necessary, lower your radon levels.” Buyers should remember that a disclosure tells you what the seller knows, not the radon level. “No known tests” means only that.
Renting: four states, then general law
In most of the US, no law written for radon makes a landlord test a rental or fix a high result. We found four states with radon laws aimed at rentals, and they do different things:
- Maine. The only one that requires a test. A high result lets either side end the lease on 30 days’ notice. Mitigation is recommended, not required.
- Colorado. No duty to test, but a signed disclosure before the lease. Since 2026 the tenant’s right to void the lease applies only to leases longer than one year. The disclosure duty has no such limit.
- Illinois. No duty to test, but a signed disclosure before the lease or on request. A tenant has 90 days from the start of the lease to test, and may end it if the result is above the action level and the landlord doesn’t mitigate.
- Florida. A fixed notice on at least one lease document, and nothing more in the radon statute.
Elsewhere the question falls to general landlord-tenant law, which rarely mentions radon. EPA’s old Radon Guide for Tenants says most states require owners generally to keep their properties “habitable”, but we didn’t research court decisions and can’t say how a court in your state would treat radon. A tenant can still ask whether the building has been tested, test if nobody has, and put a high result in writing to the owner. Don’t install anything yourself, or end a lease or stop paying rent on your own reading of a website. Our guide to radon rules for landlords and tenants sets out each state’s text and the time limits.
If the result is high
EPA’s guide for sales says: “Fix the home if the radon level is 4 picocuries per liter (pCi/L) or higher.” It adds: “Radon levels less than 4 pCi/L still pose a risk and, in many cases, may be reduced.” So 4 is a decision point, not a safety line. A close number is uncertain too: EPA says two short tests averaging 4.1 give about a 50 percent chance the year-round average is somewhat below, or above, 4. Our test result reader gives EPA’s next step for any number.
In a sale, EPA says “the buyer and seller should discuss the timing and costs of radon reduction.” We found no federal rule on who pays for a test or a fix, so it’s negotiated. Settle it before you’re bound. EPA suggests the contract spell out:
- Who does the test, what type, where and when
- How buyer and seller share the results and test costs
- When radon mitigation measures will be taken, and who will pay for them
Your agent or lawyer can write this up for your state, and our mitigation cost calculator works through a fix. If it happens before closing, test again afterward: EPA recommends “an independent, qualified radon tester”.
Your next step
EPA’s advice to buyers is short: “Ask the seller for their radon test results.” And “If the home has not yet been tested, you should have the house tested.” Before you sign anything, ask:
- Your inspector: Is a radon test included? When will I get the result?
- The seller: When was the house last tested, by whom, on which floor?
- Your lender: Do you have a radon condition of your own? Can I see it in writing?
- Your landlord: Has this building been tested, and may I see the report?
- Your state radon office: What does my state require of sellers, landlords and testers? EPA keeps contacts by state.
Sources checked on 4 November 2026.
