How Fire Alarms Work

A fire alarm system is one of the main security systems of a modern building. Its reliable operation depends on people’s safety and the prevention of significant material losses. Therefore, it is important to understand its elements and how it works.

Main Functions Of The Fire Alarm System

To understand how the fire alarm system works, it is necessary to determine its tasks.

The main functions of such a system are as follows:

  • To detect signs of fire in the serviced object at the earliest possible stage;
  • Urgently transmit an alarm signal to the dispatch panel of the response service;
  • To provide notification to people in the facility about the emergency.

The alarm system’s trigger allows timely evacuation from the facility and prompt fire extinguishing. This eliminates the threat to people’s lives and health, quickly localizes and extinguishes the fire, and thus prevents major material damage.

What A Fire Alarm System Consists Of

The scheme of the fire alarm device consists of the following main components:

  • Detectors – sensors that detect signs of fire in the object;
  • Control and information reception panels, which receive and process signals on sensor actuation;
  • Data transmission channels;
  • Sirens are devices that provide notification to people in the facility about fires.

The automatic fire alarm system is organized so that when any of the sensors is triggered, a signal is immediately sent through the data transmission channels to the control panel, which processes the information and transmits it to the dispatching computer. At the same time, the sirens are activated to warn people to evacuate.

Design And Operating Principle Of Detectors

Detectors are sensors that detect the appearance of various signs of fire. These signs include smoke in the air, rapid temperature rise, and intense glow. Fire detectors work by analyzing these factors.

There are five main types of fire detectors:

  • smoke detectors;
  • heat sensors;
  • flame sensors;
  • combined sensors;
  • manual detectors.

In this article, we will focus on smoke detectors.

Smoke Detectors

A standard smoke detector comprises a detachable housing with an electronic board and an optical system inside. The installation scheme for smoke detectors requires their placement on the ceiling because smoke rises upwards during a fire and concentrates under the ceiling.

When smoke appears and accumulates in the space under the ceiling, it penetrates the device’s housing. This triggers the sensor’s optical system, which consists of an LED, which generates a beam of light, and a photocell, which produces an electrical impulse when light hits it.

A peculiarity of the optical system design is that in a normal state, the light beam from the LED does not hit the photocell. If there is smoke, its particles refract light, which illuminates the photocell and produces an electrical impulse. This generates a signal, which is transmitted to the alarm system’s receiving device.

Smoke detectors are also sensitive to the ingress of water vapor or gases into the housing, which causes the refraction of light rays. This leads to false activation of the fire alarm system. Therefore, such detectors are not installed in showers, bathrooms, kitchens, and other rooms. They are also not installed in places for smoking.

Installation of smoke detectors is reasonable in places where a fire can emit a sufficient amount of smoke from smoldering insulation of electrical wires, fabrics, and other materials. 

Does The Smoke Detector Need To Be Replaced?

If a smoke detector is approaching 5 years old, it is nearing the end of its useful life and should be replaced. Some people think their smoke detector only works when there is smoke, but it is always on, monitoring the air 24 hours a day. 

Like other electrical equipment, smoke detectors wear out over time. A smoke detector that has been used for 5 years will have a reduced fire detection function, so it is best to replace it sooner.

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