What do smoke detectors primarily rely on to initiate an alarm signal?

Smoke detectors primarily rely on the presence of smoke particles to initiate an alarm signal. When a fire occurs, it generates smoke as a result of combustion, and this smoke consists of various particles and gases. There are primarily two types of sensor technologies used in smoke detectors: ionization and photoelectric.

Ionization smoke detectors use a small amount of radioactive material to create an electric current. When smoke enters the detector, it disrupts this current, triggering the alarm. Photoelectric smoke detectors, on the other hand, utilize a light source and a light sensor: when smoke particles enter the chamber, they scatter the light away from the sensor, which also triggers the alarm.

Understanding the operation of smoke detectors emphasizes the importance of smoke as the key indicator of fire. In contrast, options like heat, sound, or light from flames do not serve as the primary detection mechanisms in typical smoke alarms, highlighting the specialized function of smoke detection in fire safety systems.