A FAS (Fire Alarm System) has many devices that work together in the presence of different toxic gasses, fire, smoke, and other emergency condition, to notice and alert people through different viewable and audio devices. Smoke detectors and/or heat detectors can automatically activate alarms. The fire or any other alarm may also be triggered by manual fire alarm switch which is known as manual call points or breaks glass or pulls switch.

It can also be loudspeakers, followed by a recorded or instant voice message that warns people in the building not to use elevators. Fire alarm sound alerts can be set at secure frequencies and different tones, including low & high bandwidths, depending on the standards of different countries and different manufacturer of the devices. Smaller installations can set the alarm to the lower volume and larger buildings can set alarms to a higher level.