Fire Detection & Alarm System

Fire Detection & Alarm System

Fire detection systems are designed to discover fires early in their development when time will still be available for the safe evacuation of occupants. Early detection also plays a significant role in protecting the safety of emergency response personnel. Property loss can be reduced and downtime for the operation minimized through early detection because control efforts are started while the fire is still small. Most alarm systems provide information to emergency responders on the location of the fire, speeding the process of fire control.

To be useful, detectors must be coupled with alarms. Alarm systems provide notice to at least the building occupants and usually transmit a signal to a staffed monitoring station either on or off site. In some cases, alarms may go directly to the fire department, although in most locations this is no longer the typical approach.

These systems have numerous advantages as discussed above. The one major limitation is that they do nothing to contain or control the fire. Suppression systems such as automatic sprinklers act to control the fire. They also provide notification that they are operating, so they can fill the role of a heat detection-based system if connected to notification appliances throughout the building. They will not, however, operate as quickly as a smoke detection system. This is why facilities where rapid notice is essential, even when equipped with sprinklers, still need detection and alarm systems.

The most basic alarm system does not include detection. It has manual pull stations and sounds only a local alarm. This level of system is not what is typically used; it relies on an occupant to discover the fire, which can cause a significant delay. The more quickly you want to be notified of the fire, the more costly the system you must install. Speed of detection is expensive. The slowest system to detect a fire is a heat detector, which is also the least expensive. An air-aspirating smoke detection system provides the most rapid indication of fire, but these systems are five to 10 times as expensive.

Components of Fire Detection & Alarm System

  • 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.
  • Initiating devices: This component acts as an input to the fire alarm control unit and is either manually or automatically actuated. Examples would be devices like
    • Manual pull stations : Designed for raising the alarm manually by breaking the glass / pulling the handle / pushing the button
    • Heat detectors: Automatically detects the heat through thermal sensitive element inside the detector.
    • Smoke detectors: Automatically detects the smoke through optical (photoelectric) or by physical (ionization) principle.
    • Flame detectors: Automatically detects the flame through optical (photoelectric) or by physical (ionization) principle.
    • Gas leak detectors: Automatically detects the gas leak through electrochemical methods.
    • Water flow detectors: Automatically detects the flow through electromechanical method.
    Types of detectors include beam, photoelectrical, aspiration, and duct.
  • Notification appliances: 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 Flashing light, Strobe light, electromechanical horn, Beeper horn, chime, bell, speaker, Combination of above devices. The System Sensor Spectralert Advance Horn makes a beeping sound and electromechanical sound together.
  • Cables: The cables are generally used to connect the initiating devices, control panel & notification devices.