Fire & Gas

What are the components involved in a Fire Alarm system?

A fire alarm system would provide protection for life and property. The major purpose of a fire alarm system is to detect the fire and then notify the occupants in the building. Thus, the evacuation can be easily carried out; it would also notify the fire suppression system and thereby fire can be controlled. By utilizing a fire alarm system, we can protect the building or facility. The fire alarm system would also notify the fire service and because of this, the damage due to fire can be reduced.

The operation of a fire alarm system is carried out by several devices. There are input and output devices in a fire alarm system. There is remote controlling equipment in a fire alarm system and it will alert the remote monitoring centre (Emergency Control Room (ECR)). The input devices are mostly fire sensors to detect the presence of fire and also there are final control elements which are the notification and fire suppression devices.

Emergency Control Room (ECR)

The different elements of a fire alarm control unit are depicted in this below diagram.

 fire alarm control unit

Major components in a Fire Alarm System:

Alarm initiating device circuit:

The alarm-initiating circuit will be connected to the sensors which are the initiating devices in the fire alarm system.

Notification device circuit:

The output devices or the notification devices will be connected in this circuit.

Fire Alarm control panel:

This is the part in which most of the electronics in the fire alarm system can be seen. The alarm-initiating circuits and the final control element circuits are also connected to this panel. The Control panel does supervision of the fire alarm control system.

Power supply:

The electrical power supply is an important part of the fire alarm system. There shouldn’t be any interruption in this and due to this, there are primary and secondary power supplies in the fire alarm system.


These are the initiating devices or the fire detection devices in the fire alarm control system.

a) Smoke Detector:

These sensors can detect the smoke presence in the building or the facility. Smoke detectors are of two types one is ionization type and the other is photoelectric type.

Ionization type:

In the ionizing type detectors, radioactive material and electrodes are utilized to detect the smoke.  This type of detector can easily determine the flaming fires.

Photoelectric type:

In this type, a photocell is utilized with a light source. So in case the smoke enters then there will be an interruption in the light beam.

Photoelectric type

b) Gas Detector:

In case a substance is burned then gases are produced and these gases are molecules that don’t have cohesion. The fire gas detectors can detect the gas which is created by the fire. There are certain fire gas detectors that can detect combustible gases or vapors before the ignition.

Gas Detector

c) Flame Detector:

These detectors should be placed in areas that have a good chance of creating rapidly spreading flaming fires. There are two types of flame detectors: one is ultraviolet and the other is infrared. The ultraviolet type can detect the ultraviolet radiation in the flame. Infrared detectors would detect the flame by detecting the flickering components in the flame.

 Flame Detector

d) Fixed-Temperature Heat Detectors:

Fixed-Temperature Heat Detectors

Heat detectors set to predetermined temperature ratings should be installed in ceilings in areas that are expected to accumulate heat. Since heat is a by product of combustion, devices that make use of one of the three physics fundamentals listed below can detect the existence of heat:

1. Heat makes a variety of materials expand.

2. Certain materials melt when exposed to heat.

3. Materials that have been heated have noticeable thermoelectric characteristics.

e) Manual Break-glass unit:

A manually operated unit is called the break glass unit. A person is required to break the glass in case of a fire. While breaking the glass the alarm system will be activated.

Manual Break-glass unit

Final Control elements:

The final control elements are the elements that are used to control, notify or reduce the fire. This is the fire suppression system which plays the final part in a fire alarm system.

1. Deluge sprinkler system:

In this type of fire suppression system, the water will flow from each sprinkler at the same time during the activation of the system. In the deluge-type sprinkler system, the sprinkler heads are always open.

Deluge sprinkler system

2. Firewater Sprinklers:

In this type of fire suppression water is utilized to control the fire. This type of system is composed of a water supply system. This supply system will give the required water flow to the piping system. The sprinkler system would have an operating temperature the sprinklers would activate when they are heated. Sprinklers would be connected in this piping system so that during any emergency situation it will operate.

Firewater Sprinklers

3. Emergency Fire Water injection pumps:

The injection pumps are utilized when the water comes from a static source. This pump will increase the speed of the water in the piping system. It will increase the water pressure in the piping system. Large fire fighting water pumps are usually powered by diesel engines. Because of the size and quantity of flammable liquids in the facility, multiple large (2,500 to 5,000 gpm) fire protection water pumps are required.

Emergency Fire Water injection pumps

4. Fixed fire extinguishing/suppression systems:

Fixed fire extinguishing/suppression systems are often used to protect areas with valuable or important equipment, like electrical switchgear rooms, data processing rooms, telecommunication switches, and process control rooms. Their main job is to quickly put out a fire and warn people before it causes a significant amount of damage. They accomplish this by filling the protected area with a gas or chemical that puts out fires.

Fixed fire extinguishing/suppression systems

5. Hooter/Beacon:

The Hooter in a fire alarm system will alarm the occupants in a building in case of a fire. It will indicate the fire by sounding. Hooters are mostly audio indicators while Beacon could provide an audible and visual warning.

6. Fire Alarm flashlight:

These are the visual alarming system, this type of notification system is utilized in high-noise environments. This type of signalling would be beneficial for people who do have hearing problems.

Fire Alarm flashlight

Rabert T

As an electrical engineer with 5 years of experience, I focus on transformer and circuit breaker reliability in 110/33-11kV and 33/11kV substations. I am a professional electrical engineer with experience in transformer service and maintenance. I understand electrical principles and have expertise troubleshooting, repairing, and maintaining transformers, circuit breakers, and testing them. Tweet me @Rabert_infohe

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