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

Smoke and carbon monoxide alarms in the City of San Mateo are regulated by the California Residential Code (CRC R314 for smoke alarms, R315 for CO alarms) as adopted in SMMC Title 23, by SMMC Chapter 23.28 (Fire Code, adopted by Ordinance No. 2016-12), and by California Health & Safety Code Sections 13113.7 (smoke alarms) and 17926 (CO alarms). Smoke alarms approved and listed by the State Fire Marshal must be installed in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each additional story of the dwelling, including basements and habitable attics. Activation of one alarm in a unit must activate all alarms in that unit (interconnection), with limited exceptions where alterations do not expose wall and ceiling structure and no attic, basement, or crawl space provides access for new wiring. Carbon monoxide alarms are required in any dwelling with a fuel-burning appliance, fireplace, or attached garage. New construction requires hardwired alarms with battery backup; existing dwellings may use battery-only alarms when no interior finishes are removed. Effective January 1, 2011, any residential permit with a valuation exceeding $1,000 triggers required installation of compliant smoke and CO alarms throughout the residence. Sellers of existing single-family dwellings must certify compliance with smoke and CO alarm requirements at point of sale under California Health & Safety Code 13113.8 and 17926. San Mateo Consolidated Fire (the city's fire service provider, reachable at 650-522-7940) handles inspections and enforcement and recommends monthly testing and annual battery replacement, or 10-year sealed-battery alarms.