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A brief guide to fire detection and alarm system

A brief guide to fire detection and alarm system

What is fire detection? 

Fire detection is a system designed to help identify the presence of fires early in their development. Detection is followed by an alarm signalling the threat of a potential fire. This gives us time to respond effectively. 

Early fire detection also helps emergency response personnel, 

  • Giving them enough time to react before the fire is unmanageable. 
  • Loss of property can be reduced 
  • Downtime for operations is minimised through early fire detection, as control efforts can begin while the fire is still small.

Another common function of a fire detection system is the transmission of an alarm signal or notification, sent to the fire department/control room or other emergency services. 

The system may also work towards shutting down electrical and air handling equipment such as HVAC or special process operations and can be used to initiate automatic suppression systems.


About fire detection and alarm systems 

Fire detection systems are set up to trigger the fire alarm systems thus making them connected devices. There are three primary components in a fire detection & alarm system

  • Input 
  • Control Panel 
  • Output 

A fire alarm system consists of fire sensors, such as smoke and heat detectors, located throughout the building, connected to the main alarm panel by special cables. The panel is in turn connected to a set of hooters or speakers that give an audible alarm throughout the building and its surrounding areas. 

A smoke detector is used across various areas of the building, whereas kitchens are usually fitted with heat detectors.

Differences between Fire detectors & Fire Alarm: 

Function

Detectors: A smoke detector is a device that is designed to sense when there’s smoke or any type of combustion occurring. A heat detector is triggered when there is a change in temperature. 

These detectors will sense the changes and may or may not make noise when they do so, instead;

Alarm: A fire alarm is triggered  by the detectors to alert about a potential fire.

Uses

Smoke detectors are generally seen in smaller homes while fire alarms are used in larger buildings.

People with fire alarms typically have more options than those with smoke/heat detectors as the fire alarm is a robust and connected system as compared to just having a smoke/heat detector.

Components

A fire alarm system will have the following components:

  • Sprinkler systems to put the fire out immediately
  • Alarm box to call authorities as soon as the system is triggered
  • Transmitters to call for help if the resident is elderly or otherwise impaired
  • Warning lights for those with hearing impairments

Whereas a detector is just part of the larger system. 


Fire detection and suppression system: 


Fire Detection: 

Fire detection is the first step in the entire process of fire safety. Fire detection systems are usually connected to other components such as control panels & fire alarms as mentioned earlier. Part of a sophisticated/robust system will also include a suppression system. 

Detectors can be of various types. The major categories are 

  • Heat 
  • Smoke
  • Flame detectors. 

Within each category, there are numerous additional specific types. Below we will cover those, most commonly used for building fire detection and alarm activation. 

Several varieties of detectors, such as flame detectors, are used primarily to activate suppression systems.


1. Heat detectors 

These are the most basic detection devices and are divided into two major categories; spot and line detectors. 

Spot detectors are single units installed in single locations throughout the protected area and are more commonly used,

Line detectors provide a continuous detector throughout the area of coverage and are reserved for special situations.


2. Smoke detectors


The most common types of smoke detectors are: 

Photoelectric smoke detectors operate based upon light scattering within the detection chamber of the detector. Light is projected through the chamber and will be scattered if it strikes smoke. This light, reflected off the smoke in the chamber, is detected by a photocell.

Ionization smoke detectors commonly used in a home setting detects particles in smoke. As smoke passes through the chamber, the particles are ionised. These particles may then be detected by charged plates in the detector. Smoke detectors are also available in combination with a heat detector. A beam-type detector operates when the beam is interrupted by obscuring smoke between the laser emitter and receiver. These detectors are most often used in areas of large open spaces.


3. Flame Detectors


Flame detectors can be utilised in various hazardous environments, such as hydrogen stations, industrial heating and drying systems, industrial gas turbines, domestic heating systems and gas-powered cooking devices. Their primary objective is to reduce risks associated with combustion. Vert often, a flame sensor will respond more swiftly than a heat or smoke detector. 

Types of flame detectors include Ultraviolet flame sensors, Near IR array flame sensors (visual flame sensors),  Infrared flame sensors and IR3 flame detection sensors


Fire Suppression:

Fire suppression systems are built to extinguish fires via the application of fire suppression agents such as water, foam, or chemical agents. These systems are commonly designed or built with components to detect aspects like extreme heat, smoke, or fire to trigger a response.

Suppression systems  can be categorised under 


Indirect and Direct Release Systems

An indirect release system employs heat/flame sensitive detection tubing to detect fires and activate the system. The tubing itself will rupture when exposed to high heat or flames, releasing pressure and causing the indirect valve to activate. The valve then diverts the flow of the suppression agent to the larger outlet ports. 


A direct release system utilises heat and flame-sensitive tubing as a detection device and for suppressant delivery. During a fire, the portion of the tube nearest the point where the most heat or fire is detected, the tubing ruptures, creating a hole. The suppressant agent is released through this hole.

Direct release systems are recommended for the protection of electrical cabinets while indirect release systems are often best suited for protecting high-value equipment like vehicles and CNC machines.


Co2 fire suppression systems are one of the foremost fire fighting devices that are used to extinguish fires, primarily by lowering the level of oxygen, which supports combustion in a protected area. This mechanism of fire suppression makes Co2 suppression systems highly effective and requires minimal clean-up. It should normally be used in unoccupied hazard locations or else avoided by personnel when discharged.


Various methods used to detect fire

Modern-day fire detection systems comprise microprocessor-equipped cabinets with individual specialised devices attached to the cabinet by wiring and communication protocols. These devices may include the following:

  • Smoke detectors
  • Heat detectors
  • Control units for fans and doors
  • Visual indication devices (strobes)
  • Audio devices (speakers, horns)

These complex fire alarm systems, are also referred to as fire alarm control panels, and are usually connected to a computer that loads site-specific information, including the assignment of devices, naming of devices, indication protocols and messages, and the sequence of operations for control devices and indicators. 

Options for systems operations usually include the amount of time a detector must remain in the alarm condition before a general alarm is announced, the length of time audible signals must remain activated with a general alarm, and the type of messages displayed for given conditions. 

Large buildings and building complexes are usually equipped with multiple cabinets containing supporting devices. The cabinets within zones are linked to a common network. These systems may be smart enough to monitor and announce conditions such as dirty smoke detectors, missing devices, and open or ground fault conditions as well. Installation and maintenance of a fire alarm system are governed by codes and standards. The National Building Code of India covers the detailed guidelines for the construction, maintenance and fire safety of the structures.

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