A Fire Alarm System has a number of devices working together to detect and warn people through visual and audio appliances when smoke, fire, carbon monoxide or other emergencies are present. These alarms may be activated automatically from smoke detectors, and heat detectors or may also be activated via manual fire alarm activation devices such as manual call points or pull stations. Alarms can be either motorized bells or wall mountable sounders or horns. They can also be [(speaker strobes]) which sound an alarm, followed by a voice evacuation message which warns people inside the building not to use the elevators (Optional).

These are an early warning system for industrial or residential complexes. A Fire Alarm System is a passive system, meaning it does not stop the fire / Leakage from spreading. It means that the Fire Alarm System does not actively fight the fire / Leak. The main function of a Fire Alarm System is to give an early warning, that the fire has taken place in the factory or residential complex. This means that, the people in proximity to that area have an early warning to evacuate the building. However the fire will continue to burn, unless if an active system like Fire Hydrant System or Fire Sprinkler System is engaged.

The second function of the Fire Alarm System is to, alert the responsible authorities. Here the authorities may be the local Fire Department or the Emergency Action team.

The third function is to support the Fire Brigade, when they enter the building on fire. A Fire Alarm System also provides necessary emergency lighting, so that the Fire Team can navigate through the smoke and the dust.

There are two types of Fire Alarm Systems, based on the detection of location of fire :

1) Addressable Fire Alarm Systems

2) Non- Addressable Fire Alarm Systems

Addressable Fire Alarm Systems :

Addressable Fire Alarm Systems are also called Smart Fire Alarm Systems. This is because along with detection of fire they provide the location of the fire. As and when the fire spreads the FAS, alert accordingly. In addition they may provide an array of other specific services. Up to 250 devices may be connected, to the main control panel of the Fire Alarm System. Fire Alarm Companies in India, have made great strides to make the system more effective and user friendly.

Non-Addressable Fire Alarm Systems :

Non-Addressable Fire Alarm Systems are simple FAS. Their primary function is to alert the occupants that a fire has taken place.

Parts of FAS /FDS

• Fire alarm control panel (FACP) AKA fire alarm control unit (FACU); This component, the hub of the system, monitors inputs and system integrity, controls outputs and relays information.
• Primary power supply: Commonly the non-switched 120 or 240-volt alternating current source supplied from a commercial power utility. In non-residential applications, a branch circuit is dedicated to the fire alarm system and its constituents. "Dedicated branch circuits" should not be confused with "Individual branch circuits" which supply energy to a single appliance.
• Secondary (backup) power supplies: This component, commonly consisting of sealed lead-acid storage batteries or other emergency sources including generators, is used to supply energy in the event of a primary power failure. The batteries can be either inside the bottom of the panel or inside a separate battery box installed near the panel.
• Initiating devices: These components act as inputs to the fire alarm control unit and are either manually or automatically activated. Examples would be devices such as pull stations, heat detectors, and smoke detectors. Heat and smoke detectors have different categories of both kinds. Some categories are beam, photoelectric, ionization, aspiration, and duct.
• Fire alarm notification appliance: This component uses energy supplied from the fire alarm system or other stored energy source, to inform the proximate persons of the need to take action, usually to evacuate. This is done by means of a pulsing incandescent light, flashing strobe light, electromechanical horn, siren, electronic horn, chime, bell, speaker, or a combination of these devices. Strobes are either made of a xenon tube (most common) or recently LEDs.
• Building safety interfaces: This interface allows the fire alarm system to control aspects of the built environment and to prepare the building for fire, and to control the spread of smoke fumes and fire by influencing air movement, lighting, process control, human transport and exit.