Cal. Health and Safety Code § 114149.2

(a) Every hood shall be installed to provide for thorough cleaning of all interior and exterior surfaces, including, but not limited to, the hood, filters, piping, lights, troughs, hangers, flanges, and exhaust ducts. (b) Exhaust ventilation hood systems in food preparation and warewashing areas, including components such as hoods, fans, guards, and ducting, shall be designed to prevent grease or condensation from draining or dripping onto food, equipment, utensils, linens, and single-use articles. (c) Filters or other grease extracting equipment shall be designed to be readily removable for cleaning and replacement if not designed to be cleaned in place. (d) Every joint and seam shall be substantially tight. No solder shall be used, except for sealing a joint or seam. (e) When grease gutters are provided they shall drain to a collecting receptacle fabricated, designed, and installed to be readily accessible for cleaning. (f) Exhaust hood ducting shall meet the following requirements: (1) All seams in the duct shall be completely tight to prevent the accumulation of grease. (2) The ducts shall have sufficient clean-outs to make the ducts readily accessible for cleaning. (3) All ducts in the exhaust system shall be properly sloped. (4) Intake and exhaust air ducts shall be cleaned and filters changed so they are not a source of contamination by dust, dirt, and other materials.