The terms smoke alarm and smoke detector sometimes are used interchangeably to refer to smoke alarms. Although smoke alarms contain a smoke detection device, the two terms refer to different pieces of equipment.
Smoke alarms are self-contained units with a sensor that detects smoke, and an audio and/or visual stimulus to alert occupants of a fire. Smoke detectors are not self-contained and must be wired with an additional alarm system to alert individuals in an emergency.
Smoke detectors work on a circuit, which relays information to a central control module. The control module then sounds an alarm. Smoke alarms function similarly, but all the wiring and components are housed in one unit. Smoke alarms can be wired to work in conjunction with other alarms in your home. When one smoke alarm detects a fire, all smoke alarms on a wired circuit will sound.