The bill amends Chapter 5-20.8 of the General Laws by introducing a new section that mandates radon inspection and mitigation for residential real estate transactions. It defines key terms such as "radon," "radon test," and "unsafe radon levels." A radon test must be conducted no earlier than one year prior to the closing date of the transaction, and the results of this test must be disclosed to both the buyer and seller, as well as any lender involved in the transaction. The seller is responsible for the cost of the radon test and must allow the buyer to conduct an independent test if requested.

If the radon test indicates unsafe levels, defined as exceeding 4.0 picocuries per liter (pCi/L), the seller is required to install a radon mitigation system before the closing of the sale, also at their expense. Additionally, a follow-up radon test must be performed after the installation of the mitigation system to ensure its effectiveness, with the seller covering the costs of this test as well. The bill specifies certain transactions that do not require radon testing, including those involving foreclosure, tax sales, or transfers for non-residential use. The act is set to take effect upon passage.