San Mateo County, CA Fire Regulations: Smoke Detectors (2026)

San Mateo County has not adopted a separate local smoke-alarm ordinance; smoke detector requirements in unincorporated dwellings come from California Health & Safety Code section 13113.7 and the state Building and Fire Codes, enforced through county building and fire officials. Section 13113.7 requires working smoke alarms in every 'dwelling unit intended for human occupancy,' including single- and two-unit dwellings, apartments, condominiums, hotels, motels, lodging houses, and factory-built housing. Since July 1, 2014, the State Fire Marshal has required all solely battery-operated smoke alarms sold or installed in California to contain a non-replaceable, non-removable battery capable of powering the alarm for at least 10 years. Smoke alarms must be replaced 10 years from the date of manufacture marked on the unit. California Building Code requirements (applied at sale, alteration, or permit) call for smoke alarms in each sleeping room, outside each sleeping area, and on every level of a dwelling, with interconnection and hardwiring for new construction. Carbon monoxide alarms are separately required under Health & Safety Code section 13260 et seq. (the Carbon Monoxide Poisoning Prevention Act) in dwellings with fuel-burning appliances or attached garages. Landlords are responsible for installing and maintaining alarms in rental units. Because much of unincorporated San Mateo County lies in a high wildfire area, working smoke alarms are a critical early-warning safeguard.