California law requires smoke detectors in every "dwelling intended for human occupancy," including single-family homes. Specifically, detectors must be installed in every bedroom, outside every sleeping area, and on every level of the home, including basements and attics if they are part of the living space.
Here's a more detailed breakdown from anka security:
Mandatory Locations:
Smoke detectors are required in all bedrooms, outside every sleeping area (such as hallways), and on every level of the home.
Living Areas:
If there are no bedrooms on a level, detectors should be placed in the living room, den, or family room, or near stairs leading to upper levels, or both, according to the National Fire Protection Association (NFPA).
Compliance:
Smoke detectors must be installed according to the manufacturer's instructions and must be approved and listed by the State Fire Marshal.
Existing Homes:
The City of Del Mar, California, says that while the law focuses on new construction, the same configuration (detectors in every bedroom, hallway, and on every level) is recommended for existing homes.
Regular replacement: According to the First Alert Help Center, smoke alarms, including those with ten-year batteries, should be replaced every ten years or sooner if they do not work properly when tested.