Smoke alarms must receive their primary power from the building wiring and must be equipped with a battery backup. Smoke alarms with integral strobes that are not equipped with battery backup must be connected to an emergency electrical system. Smoke alarms must emit a signal when the batteries are low. Wiring must be permanent and without a disconnecting switch other than as required for overcurrent protection.
Exceptions:
1. Smoke alarms are allowed to be solely battery powered in areas of buildings erected for or converted to residential use before June 1, 1984, where interior work requiring a permit has not taken place since June 1, 2020.
2. Smoke alarms are allowed to be solely battery powered in areas of buildings erected for or converted to residential use before June 1, 1984, undergoing alterations or repairs that do not result in the removal of interior wall or ceiling finishes exposing the structure, unless there is an attic, crawl space, or basement available that could provide access for installing wiring without the removal of interior finishes.