Cal. Health and Safety Code § 13005

Every person is guilty of a misdemeanor who: (a) Sells, offers for sale, leases, or rents to any person any tractor, engine, machine, or truck equipped with an internal combustion engine that uses hydrocarbon fuels, if either: (1) It is specifically designed for use in harvesting or moving grain or hay or for use on land covered with any other flammable agricultural crop, unless the exhaust system of the engine is equipped with a spark arrester in effective working order or the engine is constructed, equipped, and maintained for the prevention of fire pursuant to Section 4443 of the Public Resources Code. (2) It is not specifically designed for any of the uses described in paragraph (1) but could be used for any of those uses, unless the person provides written notice to the purchaser or bailee at the time of sale or at the time of entering into the lease or rental contract stating that the use or operation of the engine on any flammable agricultural cropland is a violation of subdivision (b), unless the exhaust system is equipped with a spark arrester in effective working order or the engine is constructed, equipped, and maintained for the prevention of fire pursuant to Section 4443 of the Public Resources Code. (b) Operates or causes to be operated any tractor, engine, machine, or truck equipped with an internal combustion engine that uses hydrocarbon fuels in harvesting or moving grain or hay, or on land covered with any other flammable agricultural crop, unless the engine is equipped with a spark arrester maintained in effective working order or the engine is constructed, equipped, and maintained for the prevention of fire pursuant to Section 4443 of the Public Resources Code. Spark arrester, as used in this section, is as defined in Section 4442 of the Public Resources Code. Spark arresters attached to the exhaust system of engines on equipment or vehicles, as described in this section, shall not be placed or mounted in such a manner as to allow flames or heat from the exhaust system to ignite any flammable material. Motortrucks, truck tractors, buses, and passenger vehicles, except motorcycles, are not subject to the provisions of paragraph (2) of subdivision (a) if the exhaust system is equipped with a muffler as defined in the Vehicle Code.