In 1973, when smoke alarms were first introduced, only one was required for an entire house, but the requirements in California have changed since then. In new construction, a smoke alarm must be installed in every sleeping room as well as in a central location in the hallway outside the bedrooms. If a house has more than one story, there must be a smoke detector on each floor, including the basement and attic, if these are habitable. Smoke detectors aren't required in unfinished attics or crawl spaces. If a floor is divided into rooms at different levels, a smoke alarm in the higher of the two rooms can serve both of them, provided they aren't separated by more than one story.
Hardwired and Battery-Powered Alarms
With some exceptions, California requires smoke alarms be hardwired into the main electrical panel and have battery backups. The exceptions include buildings that don't receive power from a commercial power company, for example, homes that are off the grid and existing homes with working fire alarms that are not undergoing construction. One of the changes announced by the fire marshal -- effective July 1, 2015 -- makes removable batteries obsolete. All smoke alarms, whether they are powered solely by batteries or hardwired, must contain a non-removable, non-replaceable battery with a life span of 10 years.
When Replacement is Required
If your existing smoke alarms don't conform to regulations and are still working, you aren't required to change them unless you undertake improvements requiring a permit and costing more than $1,000. Building inspectors are not allowed to sign off on any new construction or renovation permits issued after July 1, 2014 unless all smoke detectors are installed in accordance with current regulations. If you are required to install new smoke detectors, the smoke detectors must be interconnected in such a way that they all go off when one of them is triggered. As of January 1, 2015, all smoke detectors sold in California must include a hush feature that allows you silence the alarm for a few minutes.
Smoke alarms need regular testing and occasional maintenance and, according to the updated regulations, landlords must perform all installation and maintenance. Landlords are allowed to enter rented dwelling units to perform this maintenance as long as they provide tenants with reasonable notice. The building code defines reasonable notice as 24 hours in the absence of serious circumstances. In another change in California regulations, manufacturers must affix a label listing the date of manufacture of each unit and providing a place to write the date of installation to make it easier to conform to the 10-year replacement requirement.