Radon Laws in Montana: Testing, Disclosure & Mitigation Rules

The Short Answer

Montana regulates radon primarily through a strict statutory real estate warning and disclosure mandate codified in the Montana Radon Control Act. Under Montana Code Annotated (MCA) § 75-3-606, residential real estate transactions must incorporate a mandatory verbatim statutory warning statement signed by the purchaser, accompanied by copies of any available radon test results or mitigation records. Montana does not license radon testers or mitigators through a state licensing board, directing consumers to national NRPP and NRSB certification registries. Geologically, Montana is heavily elevated, with 45 of its 56 counties designated as EPA Zone 1.

Testing Requirements

Indoor radon testing is voluntary for private residential homeowners and landlords under Montana law; the state does not compel owners of existing single-family dwellings or rental properties to test indoor air. In addition, Montana statutes do not mandate routine radon testing in public or private K-12 school buildings or commercial child care centers, although the Montana Department of Environmental Quality (DEQ) strongly encourages school administrators to test voluntarily using standardized EPA and ANSI/AARST protocols.

Real-Estate Disclosure

Real estate disclosure is strictly mandated under the Montana Radon Control Act, Montana Code Annotated (MCA) §§ 75-3-601 to 75-3-607. Under MCA § 75-3-606, prior to or contemporaneously with executing any contract for the purchase and sale of residential real property, the seller must provide the buyer with a document containing a specific, verbatim statutory radon warning statement in prominent lettering. The buyer must sign an acknowledgment confirming receipt of the notice. Furthermore, if the property has ever been tested for radon or has undergone mitigation treatments, the seller must deliver copies of all available test reports and mitigation documentation. The statute requires disclosure of known conditions, but does not obligate sellers to conduct new testing.

Mitigator & Tester Certification

Montana has no state licensing requirement for radon measurement technicians or mitigation contractors, per the Montana Department of Environmental Quality, verified November 2026. The state maintains no state-administered regulatory board or licensing exam for radon professionals. Instead, the Montana DEQ officially directs homeowners, builders, and real estate professionals to hire contractors certified through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Contractors must adhere to local municipal trade and electrical permits when installing vent fans or running electrical wiring.

New Construction

Montana does not enforce a statewide mandatory building code requiring passive Radon-Resistant New Construction (RRNC) in all new residential construction. While the Montana Department of Labor and Industry Building Codes Program oversees statewide building codes, model appendices like IRC Appendix F are not universally mandated for single-family residential construction across the state. However, individual local jurisdictions (such as Missoula, Bozeman, and Helena) and custom builders frequently adopt passive soil-gas ventilation practices voluntarily due to the state’s severe radon risk.

Radon Zones & the Action Level

According to the EPA Map of Radon Zones, Montana possesses exceptional geological radon risk: 45 out of 56 counties are classified as EPA Zone 1 (High Potential), where predicted average indoor screening levels exceed the federal action level of 4.0 pCi/L. The remaining 11 counties are designated as Zone 2 (Moderate Potential, 2.0 to 4.0 pCi/L); zero Montana counties are classified as low-risk Zone 3. Montana DEQ enforces the federal action level benchmark of 4.0 pCi/L, while advising that mitigation be considered between 2.0 and 4.0 pCi/L. For county-level geological maps, visit our EPA Radon Zone Map guide.

The State’s Radon Program

The official state educational and technical agency is the Montana Department of Environmental Quality Radon Program, based within the Energy and Indoor Air Programs. Montana DEQ provides technical guidance to homeowners, coordinates with county health departments, and offers subsidized, low-cost short-term test kits through authorized testing laboratories. Montana residents can order test kits, review county testing statistics, and locate certified contractors through the official Montana DEQ Radon Program portal or by calling the DEQ program office at 406-444-6697.

Sources & Limits

This regulatory guide is provided for educational and informational purposes only and does not constitute formal legal, building code, or engineering counsel. State statutory disclosure requirements and local building codes are subject to legislative amendment. Property buyers, sellers, landlords, and contractors should verify current rules directly with the Montana Department of Environmental Quality or a licensed Montana attorney.

Official Sources: Montana Code Annotated §§ 75-3-601–75-3-607; Montana Department of Environmental Quality (DEQ); U.S. Environmental Protection Agency (Map of Radon Zones).

To compare Montana’s statutory disclosure rules with other states across the nation, consult our master guide to radon regulations across the United States or inspect the EPA Radon Zone Map.