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

030(i) makes compliance with all applicable laws and regulations a permit condition and then lists three specific safety measures every short-term rental in the unincorporated county must have installed before the Department of Planning and Building will issue the permit. First, smoke alarms listed as complying with UL 217 and approved by the State Fire Marshal must be installed in every bedroom, just outside but in the immediate vicinity of every bedroom, and on every level of the unit, including basements and habitable attics. Second, carbon monoxide alarms complying with UL 2034 must be installed outside but near every bedroom and on every level, including basements.

Third, at least one fire extinguisher must be mounted on every habitable level. These requirements sit alongside, not instead of, the California Residential Code and California Fire Code, which the same subsection also references as applicable law. The rule reaches only short-term rentals located in the county's unincorporated pockets, places like Emerald Lake Hills, Devonshire, Montara, and the Midcoast; it does not apply inside Redwood City, San Mateo, Daly City, or the county's other incorporated cities, each of which regulates short-term rentals under its own municipal code.

Because the safety measures are written as permit prerequisites, an owner who cannot show compliant alarms and an extinguisher at inspection cannot obtain or renew a short-term rental permit, and an existing permit remains subject to the same building-standards clause for as long as the unit operates as a short-term rental.