This initiating device is the most common device and is the fastest to respond Heat Detector Beam Detector Smoke Detector Gas Detector

The correct answer is Smoke Detector.<br /><br />Smoke detectors are the most common and fastest-responding initiating devices in fire alarm systems. They are designed to detect the presence of smoke, which is an early indicator of a potential fire. Smoke detectors typically use ionization or photoelectric technology to sense smoke particles in the air. When smoke is detected, the detector sends a signal to the fire alarm control panel, which then triggers the alarm and notifies the building occupants. Smoke detectors are widely used in residential, commercial, and industrial settings due to their reliability, low cost, and ability to provide early warning of fires.