The bill amends the General Laws in Chapter 23-61, "Radon Control," to include provisions for radon testing and mitigation in rental dwelling units. It introduces new definitions relevant to rental properties and gives the director of health the authority to require radon testing in these units. The bill mandates that by January 1, 2027, landlords must test for radon every five years, with new rental properties requiring a test within the first year of tenant occupancy. Short-term rentals are exempt from this requirement. Landlords, tenants, or certified businesses can perform the testing, and the department will provide guidance on testing procedures. Tenants may request a second test, potentially at the landlord's expense, to confirm initial results.

The bill sets forth penalties for landlords who fail to comply with testing requirements, falsify results, or fail to disclose radon levels, with a civil penalty of up to $250 per unit. Landlords must disclose radon hazards in writing to current and potential tenants and report hazards and mitigation efforts to an online database. The bill also amends the "Residential Landlord and Tenant Act" to include radon testing obligations for landlords, excluding short-term rentals from these requirements. The act is effective immediately upon passage, and there are no deletions indicated in the provided text.