A fire alarm system is an active fire protection system that detects fire or the effects of fire. In so doing, it provides one or more of the following services: it notifies the occupants, notifies persons in the surrounding area, summons the fire service, and controls all the fire alarm components in a building.
Fire alarm systems can include alarm initiating devices, alarm notification appliances, control units, fire safety control devices, annunciators, power supplies, and wiring. These systems have helped save millions of lives. One drawback, however, is that such a system can be disrupted by deliberate false alarms.
Types of components
A fire alarm system is composed of components which can be classified into the following categories.
- Fire alarm control panel (FACP; or fire alarm panel) – this is a central control device involved in detecting, reporting, and acting on occurrences of fires within a building.
- Initiating devices – these devices either sense the effects of a fire, or are manually activated by personnel, resulting in a signal to the fire alarm panel. Examples are heat detectors, smoke detectors, manual pull stations, and sprinkler pressure or flow switches.
- Power supply – because one of the fire alarm system objectives is life safety, fire alarm system power supplies are redundant, and relatively very reliable as compared to electronic or electrical systems of similar complexities (for example, HVAC control systems). Primary supply is typically commercial light and power. A back-up/secondary supply is provided by sealed, lead-acid batteries. NAC power supplies for additional notification appliances beyond the original capability of the FACP. Generators are permitted under strict rules.
- Notification appliances – these devices provide stimuli for initiating emergency action and provide information to users, emergency response personnel, and occupants. Examples are bell, horn, speaker, light, or text display that provides audible, tactile, or visible outputs.
- Signaling line circuits (SLC) – the wiring which carries data information.
- Supervisory signals – detecting devices and signaling to indicate a condition in fire protection systems which is not normal and could prevent the fire protection system from functioning as intended in the event of a fire. An example is a closed valve which controls the water supply to a fire sprinkler system. This does not indicate the failure of a component or subsystem of the fire alarm system.
- Trouble signal – signaling to indicate a wiring fault. Sometimes specific components or features of the fire alarm system, of which could prevent the fire alarm or fire suppression system from functioning as intended. An example is a disconnected wire at a heat detector.