Cal. Health & Saf. Code § 18031.5
Nothing in this part or any other provision of law shall be construed to prohibit the installation of fireplaces in manufactured homes and mobilehomes. The department shall adopt any regulations for the installation of fireplaces in manufactured homes, mobilehomes, or commercial coaches which it may determine are reasonably necessary in order to protect the health and safety of the occupants and to assure that an installation does not impair the efficiency of the primary heating or cooling system of the manufactured home, mobilehome, or commercial coach. All manufactured homes, mobilehomes, and commercial coaches manufactured on or after June 15, 1976, which contain fireplaces, shall comply with the National Manufactured Housing Construction and Safety Standards Act of 1974 (42 U.S.C., Sec. 5401, et seq.).
Ca. Health and Saf. Code § 18031.5