No state in the U.S. requires every home to be tested for radon, but the states that require radon testing do so in specific settings: 13 states mandate testing in public schools, a handful of states and local jurisdictions require landlords to test rental units, and some lender programs require testing on certain multifamily loans. Separately, 37 states require home sellers to disclose any radon results they already have, and about a dozen states require radon-resistant features in new construction. Whether a legal requirement reaches you depends less on where you live than on what you are doing — buying, selling, building, renting out, or sending a child to school.
The Federal Baseline
The Indoor Radon Abatement Act of 1988 set a national goal that indoor air “should be as free of radon as the ambient air outside of buildings,” but it did not require anyone to test. Congress instead directed the EPA to fund state radon programs, publish guidance, and survey schools and federal buildings.1Office of the Law Revision Counsel. 15 USC Chapter 53, Subchapter III: Indoor Radon Abatement Everything binding happens at the state, local, or lender level.
One number from the federal side matters because state laws and lender rules borrow it. The EPA treats 4.0 picocuries per liter (pCi/L) as the action level at which a home should be mitigated, and recommends considering mitigation between 2.0 and 4.0 pCi/L as well.2US EPA. What Is EPAs Action Level for Radon and What Does It Mean That threshold reappears throughout the rules below.
States That Require Radon Testing in Schools
Thirteen states require radon testing in public school buildings: Colorado, Connecticut, Florida, Illinois, Maryland, Minnesota, New Jersey, New York, Ohio, Rhode Island, Tennessee, Virginia, and West Virginia. Testing frequency varies. New Jersey, for instance, requires every public school building to be tested at least once every five years. Some states extend the requirement to licensed child care centers in school buildings.
These laws typically require results to be reported to the state or made available to parents, and require mitigation when levels exceed 4.0 pCi/L. If you want to know whether a specific school has been tested, the state radon program or the district itself keeps the records.
Radon Testing Requirements for Rental Properties
A small but growing number of jurisdictions require landlords to test. Maine requires landlords to conduct radon testing every two years and submit results to the state health department, which publishes them online. Montgomery County, Maryland requires landlords of ground-contact and basement rental units to give tenants test results showing radon below the EPA action level, with testing performed no more than three years before the lease date.
Where no testing law applies, landlords still face real exposure. Elevated radon in a rental unit can implicate the implied warranty of habitability that exists in virtually every state. A landlord who knew about high levels and said nothing could face liability for failing to disclose a known hazard, and a tenant who develops lung cancer linked to prolonged exposure could bring a negligence claim.
Lender-Driven Testing on Certain Loans
Freddie Mac requires radon testing for multifamily properties securing its loans. At least 10 percent of all ground-contact units must be tested, with a minimum of one test per building. If any unit comes back at or above 4.0 pCi/L, the borrower must mitigate or conduct follow-up testing, and post-mitigation testing must confirm levels below 4.0 pCi/L before the loan proceeds.3Freddie Mac. Exhibit 11 Radon Testing and Mitigation Standards
For FHA-insured multifamily and healthcare facility loans, radon testing and mitigation are eligible program expenses, but HUD’s 2024 guidance explicitly says it does not impose general radon testing requirements and does not apply to single-family FHA-backed mortgages.4HUD. CPD Notice on Departmental Policy for Addressing Radon in the Environmental Review Process VA-backed home loans do not require radon testing or abatement unless a local government would otherwise place a lien on the property.5Veterans Benefits Administration. Circular 26-15-21 Property Preservation Requirements and Fees A conventional, FHA, or VA loan on a single-family home almost never comes with a radon testing requirement attached.
Disclosure Rules in Home Sales
The most widespread state-level radon obligation is a disclosure requirement, not a testing requirement. Thirty-seven states require home sellers to disclose known radon hazards or prior test results during a real estate transaction. These laws do not force sellers to test. They require sellers to share what they already know. A seller who has never tested and genuinely has no knowledge of levels in the home generally satisfies the disclosure form by checking “unknown.”
Disclosure usually takes the form of a written statement covering whether any testing was done, the results, and whether a mitigation system was installed. Utah, for example, folds radon into a broader hazardous-conditions disclosure covering the seller’s “current actual knowledge.”6Utah Department of Environmental Quality. Radon and Real Estate Transactions in Utah One practical consequence worth understanding as a buyer: sellers have a legal incentive not to test, since testing creates knowledge that must then be disclosed. A clean disclosure form is not evidence that radon is low. It is often evidence that no one looked.
Protecting Yourself With a Radon Contingency
In any state, a buyer can negotiate a radon contingency into the purchase agreement. The clause gives you the right to test during the inspection period and, if levels exceed 4.0 pCi/L, to require the seller to mitigate before closing, negotiate a price reduction, or walk away. The clause costs nothing to include and is standard in areas with known radon risk.
States Requiring Radon-Resistant New Construction
A separate set of states regulates construction rather than testing. These states require builders to incorporate radon-resistant features into new homes, typically following Appendix F of the International Residential Code: a gas-permeable gravel layer beneath the foundation slab, a plastic vapor barrier, sealed cracks and penetrations, and a passive vent pipe running from under the slab up through the roof. If later testing shows elevated levels, a small inline fan activates the system at modest cost.
The following states and the District of Columbia have mandatory radon-resistant construction requirements for new homes: Connecticut, the District of Columbia, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, New Jersey, Oregon, and Washington.7Environmental Law Institute. Radon Control in New Home Construction These rules apply to the builder at the time of construction, not to the homeowner afterward.
States That Regulate Who Can Perform Radon Testing
About 20 states have adopted credentialing requirements for radon professionals, covering roughly half the U.S. population. The requirements fall into three patterns.
- State license, certification, or registration: Florida, Iowa, Illinois, Kansas, Maine, Minnesota, Nebraska, New Jersey, Ohio, and Pennsylvania.
- Certification from a national proficiency program (NRPP or NRSB) without a separate state credential: California, New Hampshire, and Virginia.
- Both a state credential and national certification: Colorado, Connecticut, Indiana, Kentucky, Rhode Island, Utah, and West Virginia.
In states without credentialing rules, anyone can offer radon testing services. If you hire a professional in one of those states, NRPP or NRSB certification is worth asking for voluntarily, since both programs require adherence to the ANSI/AARST measurement standards. Homeowners anywhere can also test on their own with a short-term charcoal kit from a hardware store or state program for under $20, and free kits are sometimes available through local health departments.8US EPA. How Do I Get a Radon Test Kit? Are They Free?
If No Law Reaches Your Situation
For most owner-occupied single-family homes, no state or federal law requires a radon test. That silence is not reassurance. The EPA recommends testing every home regardless of state, and the 4.0 pCi/L action level applies the same way whether a law forced the test or you ordered one yourself. If you are selling, your obligation is usually to disclose what you know, not to find out. If you are buying, a contingency is cheap. If you are renting out property, check both your state and your city or county, and treat radon as a habitability issue even where no specific statute mentions it.