fire alarm system

What is Fire Alarm System and How it Works?

So many of us will have a confusion regarding Fire Alarm system and Fire Detection System. No need of confusion they both are same.

  1. What is Fire Alarm system?
  2. How do Fire Alarm System works?
  3. What are the Main Components?
  4. What are the Different Types?
  5. What are Different States of this system?

What is Fire Alarm System?

In a building, if any emergency or fire accident occurs, then the fire alarm system plays an important role in detecting the emergency and alerting the public, staff present inside the building and warn them to protect their lives and exit the building as soon as possible.

All Buildings, commercial complex, Residential buildings, offices, Industrial Buildings will have this Fire Alarm System.

This Fire alarm system is specially designed to operate in time of emergency. The main purpose of this system is to preventing the lives of the occupants present inside the building.

Now let us have a brief discussion about working principle of Fire Alarm System.

How do Fire Alarm System works?

In a short and simple understanding way I will explain you briefly, how it works at the time of emergency.

This system is a combination of several components or devices arranged in several areas of building. These all-different components together connected with a network to one another, which gives complete structure for a Fire alarm system.

Whenever an emergency or fire accident occurs in a building, for example let us assume the fire or smoke happens in fifth floor of a multi storied building. Then the following work will be done by Fire alarm system

  • The fire or smoke in fifth floor is detected by detecting devices such as Smoke detectors or Heat detectors
  • Then this detectors send signal to the control panel which is main component of fire alarm system which is fitted in main area of building. Let us say it is in ground floor.
  • Then the control panel reads the signal in which floor the emergency accident occurs and send the signal to Alarm devices.
  • This Alarm devices after getting signal from Control panel, they are triggered and activated which makes sound horn.
  • And the public or occupants present inside the building particularly in fifth floor are alerted by listening the sounds from alarm and exit from the building protecting their lives. 

Now let us have a look on different types of components or devices used.

What are the main components of a Fire Alarm System?

As we discussed above this System is a combination of several components connected with a network with each other. The following are the categories and components present in it

  1. Initiating Devices
  • Heat Detectors
  • Smoke Detectors
  • Ionization smoke detectors
  • Light scattering smoke detectors
  • Light obscuring smoke detectors
  • Sprinkler water flow sensors
  • Carbon monoxide Detectors
  • Multi sensor Detectors
  • Manual call points
  1. Indicating Devices
  • Bells
  • Horns
  • Flash Lights, Strobe Lights
  1. Fire Alarm Panel
  2. Power Supply Devices
  • Main Power
  • Battery Backup
  • Generator
  1. Auxiliary Devices

Initiating Devices

Initiating devices are the primary starting devices includes in Fire alarm system. The main purpose of these devices are to detecting the heat or smoke and send signal to control panel. Manual pull station devices also comes under these section.

Let us have a brief introduction of these devices as follows

Heat Detectors

The Heat Detectors are one of the Initiating devices used in this system. When the surrounding temperature where the heat detector is located exceeds the set temperature of this device, then it is activated. Then it send message to control panel and helps in triggering the alarm.

Most commonly these devices contains fuse like element made of eutectic alloy. When temperature exceeds, then this alloy will be melted and gets activated. It works almost same as Electrical Fuse.

Heat Detector in fire alarm system

Smoke Detectors

Generally there are three types of smoke Detectors. Such as following

  • Ionization Smoke Detector
  • Light Scattering Smoke Detector
  • Light Obscuring Smoke Detector
smoke detector in fire alarm system
Ionization Smoke Detector

This Ionization smoke detector device contains two chambers. One of this chamber contains two electrodes. There will be a flow of current between these two electrodes. When smoke air enters this chamber, then the air will be ionized by alpha particle and affects in dropping the flow of current between these electrodes. Then due to this drop flow of current results in activating the device and sends the signal to control panel to trigger the alarm.

Light Scattering Smoke Detector

In this Light Scattering Smoke Detector device a light source and Photovoltaic cell are used. These are separated by a chamber and placed in a position that not to fall light on photovoltaic cell. But when smoke enters into the chamber, the light from the light source is made scattered to fall on photo voltaic cell. Then this photovoltaic cell send the signal to control panel to trigger the alarm.

Light Obscuring Smoke Detector

This device works quite opposite to above device. In this Light obscuring smoke detector device, there will be light beam between light source and photovoltaic cell continuously. When smoke enters into this device, the amount of light falling on photovoltaic cell will be dropped. Then this drop in quantity of light will be identified by photovoltaic cell and send the signal to control panel to trigger the alarm.

Carbon Monoxide Detectors

As we all know carbon monoxide is a dangerous and poisonous gas released at the time of combustion.

These Carbon monoxide detectors are electronic detectors contains electrochemical cell. This cell senses the level of carbon monoxide present air surrounding it and gives signal to control panel.

Multi Sensor Detectors

The Multi Sensor Detectors are most accurate and sensitive ones of Fire Alarm System. These detectors collect both signals from optical detectors and as well as temperature detectors. And then finalize the by avoiding fault detections.

Manual call Points

This Manual call points or Break glass call points is a device which enables a personal/occupant/staff to raise the alarm by breaking the frangible element in it.

These are placed at easily sited areas to be identified by everyone. These are fitted at 1.4 m above finish floor level on walls. They are mostly placed at landing areas, stairways, near accessible doors, etc., the distance between the manual call points shouldn’t exceed 30 meters.

manual call point in fire alarm system

Indicating Devices

The devices which makes sound alarm loud, or indicates the emergency comes under this category. The devices like Bells, Horns, Chimes and Strobe lights (for visual alert) comes under indicating devices.

sound alarm

Fire Alarm Control Panel

This fire alarm control panel is the central main device. All devices and parts network are controlled from this device. It will have display, touch pad for programming, resetting and other functions to make by onsite personnel. It also displays the present state or condition of fire alarm system of the building.

What are the types of Fire Alarm System?

There are four different types Fire Alarm Systems present. The selection of type of fire alarm system is up to the suitable conditions of the building. These are as follows

  • Conventional
  • Addressable 
  • Intelligent 
  • Wireless 

What are the different States of Fire Alarm system?

The State in which Fire alarm system is present is indicated in Fire Alarm control panel. Almost all systems have three states as follows

  1. Normal State
  2. Alarm State
  3. Trouble State


In this above content we have so far briefly discussed about what is Fire alarm system and its parts and how it works. If you have any suggestions and comments regarding this article please comment below. 

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By Naseer Shaik

Hi, I am Naseer Shaik, Mechanical Engineer. Present working as Plumbing and Firefighting Engineer in Kuwait. And also I am a Blogger, YouTuber.

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