California Code, Health and Safety Code - HSC § 18944.21

(a) Not later than July 1, 2023, the commission shall consider whether to adopt the most recent versions of the following consensus safety standards, to be codified and published in the California Building Standards Code: American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 15-2019; ASHRAE Standard 34-2019; Underwriters Laboratories (UL) 60335-2-89 2nd edition; and UL 60335-2-40 3rd edition.

(b) If the commission does not adopt all of the consensus safety standards listed in subdivision (a), then effective July 1, 2024, no state or local building code provision shall prohibit the use of a refrigerant listed as acceptable under Section 7671k of the federal Clean Air Act (42 U.S.C. Sec. 7401 et seq.), provided each use is installed in accordance with the most recent version of ASHRAE Standard 15 and the applicable listing standard, such as UL 60335-2-89 or UL 60335-2-40.