A smoke alarm is a device that detects smoke, typically as an indicator of fire. It works by using sensors to identify smoke particles in the air. When smoke is detected, the alarm emits a loud sound to alert people nearby, giving them time to evacuate the area. There are different types of smoke alarms, including ionization and photoelectric alarms. Ionization alarms are more responsive to fast-flaming fires, while photoelectric alarms are better at detecting smoldering fires. Regular maintenance, such as testing the alarm and changing the batteries, is essential for ensuring their effectiveness in emergencies.