Fire & Gas

Types of Fire Detectors

What is the use of fire detector?

Fire detectors are essential safety devices designed to detect the presence of a fire or smoke & alert people to the conditions that may lead to a fire and save them from danger.

Many modern fire alarm systems include a combination of these detectors to furnish comprehensive fire detection and reduce false alarms.

What are the factors that depend on the selection of a fire detector?

The selection of a fire detector depends on various factors such as 

  • The specific application 
  • The type of fire hazards present, 
  • The environmental conditions of where it is installed,
  • The desired sensitivity level.
  • Location and Area Size
  • Consider the tolerance for false alarms in the specific application
  • The required response time for detecting a fire is critical

How the fire detectors are classified?

There are several types of fire detectors available in the market with various technologies to detect fires or smoke. Here are some common types of fire detectors:

Ionization Smoke Detectors

  • These Ionization detectors use ionization chambers to sense smoke particles. 
  • These detectors use the minimum amount of radioactive material to ionize the air within the detector inside a sensing chamber. 
  • When smoke particles enter the sensing chamber, they disturb the electrical current, & ionization process, which causes the detector to activate an alarm signal. 
  • Ionization detectors are most effective & particularly good in detecting fast-burning, flaming fires and are widely employed in residential settings.

Photoelectric Smoke Detectors

  • To recognize smoke, these photoelectric smoke sensors utilize a light source and a light-sensitive detector.
  • Photoelectric smoke detectors use a light source (typically an LED) and a light sensor (photodetector).
  • When smoke particles enter the sensing chamber, the smoke scatters the light rays, forcing the sensor to activate an alarm. 
  • Usually, these detectors are highly susceptible to slow smoldering fires.
  • These detectors are suitable for residential and commercial applications.
  • These detectors are more immune to generating false alarms from cooking or steam.

Heat Detectors

  • Heat detectors are intended to respond to a rise in temperature forced by a fire rather than smoke. 
  • Usually, these heat detectors are utilized in areas where smoke detectors might produce false alarms, such as kitchens or garages.
  • There are two main types of heat detectors: Fixed Temperature & Rate-Of-Rise Detectors. 

a) Fixed Temperature Detectors

These Fixed Temperature Detectors trigger an alarm signal when the ambient temperature surpasses a specified predetermined threshold pre-set level. 

b) Rate-of-Rise Detectors 

These Rate-of-rise detectors trigger an alarm for an immediate rise in temperature at a certain rate over a short period of time.

Combination Smoke and Carbon Monoxide Detectors

  • These Carbon monoxide detectors are specifically designed to sense & monitor the presence of both smoke and elevated levels of carbon monoxide (CO) gas.
  • Carbon Monoxide is odorless and colorless but can be fatal at higher concentration rates.
  • Pairing of both Carbon Monoxide Detectors & smoke detectors may provide extra security in places of residence and work.
  • CO detectors serve a vital function in identifying the presence of harmful carbon monoxide gas, which can be a typical result of fires and can be generated through incomplete combustion.

Flame Detectors

  • Flame detectors are equipped with specialized sensors that detect the presence of flames or specific wavelengths of light radiated by fires.
  • They are frequently used in industrial settings and commercial settings where early fire detection is essential, & fires that may generate intense heat and flames, but not smoke.
  • Flame detectors are used to detect the presence of flames or sudden bursts of light associated with fires. 
  • They are commonly used in areas where smoke detectors may not be effective due to the nature of the environment.

Gas Detectors

  • While not strictly fire detectors, gas detectors are used to sense the presence of combustible gases or other hazardous or toxic gases that can lead to fires or explosions. 
  • These detectors are often used in industrial settings or areas where specific gases may pose a danger.
  • These detectors are used to detect specific gases like methane or propane, which can be indicators of a potential fire or explosion hazard in commercial and industrial settings. 
  • They are essential for preventing fires in areas where gas leaks are a concern.

Spark and Ember Detectors

  • These Spark and Ember Detectors are specialized detectors designed to detect sparks, embers, or hot particles that might ignite fires in industrial settings.
  • These detectors detect the presence of small, hot particles and trigger an alarm.
  • These specialized detectors are used in environments where sparks or embers could ignite fires, such as in grain elevators or woodworking shops. 

Flame Ionization Detectors (FID)

  • FID detectors are used in laboratories and industrial settings to detect the presence of flammable gases by measuring the ionization of those gases when exposed to a flame.
  • FIDs are used in some specialized industrial applications to detect the presence of hydrocarbon fires by ionizing combustion products.

Air Aspirating Smoke Detectors (VESDA)

  • VESDA detectors use a network of pipes to actively draw in air and analyze it for the presence of smoke particles. 
  • They are highly sensitive and often used in critical facilities where early detection is crucial.
  • This advanced system uses a network of pipes and sampling points to actively draw air samples from a protected area into a central detector. 
  • It can detect smoke at its earliest stages and is commonly used in sensitive environments like data centers.

Air Sampling Smoke Detectors

  • Similar to aspiration systems, these detectors use a network of pipes to sample air for the presence of smoke particles. 
  • They are highly sensitive and suitable for critical applications.

Linear Heat Detectors

  • These detectors activate when the temperature at any point along the cable exceeds a predetermined level.
  • This detector consists of a heat-sensitive cable that can be installed in areas where traditional detectors may not be suitable, such as cable trays, conveyor belts, or ductwork. 

Beam Detectors

  • Beam detectors use a transmitter and a receiver to send a beam of light across an area. 
  • If smoke or other obstructions interrupt the beam, an alarm is triggered. 
  • These detectors are often used in large open spaces or warehouses.     

UV (Ultraviolet) Flame Detectors

  • UV flame detectors are designed to detect the presence of open flames, particularly those produced by hydrocarbon fuels such as natural gas, gasoline, or oil.
  • They operate based on the principle that flames emit ultraviolet radiation that is not present in significant amounts in typical industrial environments when there is no fire.
  • UV detectors are highly sensitive to the UV radiation emitted by flames and can respond rapidly to the presence of a fire.
  • Common applications include industrial boiler systems, petrochemical facilities, gas turbine power plants, and other environments where the detection of open flames is critical for safety.

IR (Infrared) Flame Detectors

  • IR flame detectors are designed to detect infrared radiation emitted by flames, especially hydrocarbon-based flames.
  • They operate on the principle that flames emit IR radiation that is not present in non-fire conditions.
  • IR detectors are known for their sensitivity and can detect flames from a distance.
  • They are used in applications where the detection of distant or obscured flames is necessary, such as outdoor storage tanks, large process areas, or areas with limited visibility.

Frequently Asked Questions on Fire Detectors

What is a fire detector? 

A fire detector is an electronic fire protection element that detects the presence of smoke as a key indication of fire and triggers a sound to warn to residents of that building. 

What are the primary types of fire detectors? 

Primary types of Fire Detectors

  • Heat Detector.
  • Ionization Smoke Detector.
  • Photoelectric Smoke Detector.
  • Ionization and Photoelectric Smoke Detector.

How does a smoke detector work? 

  • Smoke Detector detects fires by sensing small particles in the air up to a certain level. 
  • An alpha radiation ionizes the air within the metallic chamber. 
  • A low electric voltage is applied across the chamber to cause an electric current to flow through the ionized air. 
  • The current flow is altered when a smoke particle enters the metallic chamber to activate an alarm.

What is heat detectors used for? 

Heat Detectors used in

  • Hallways
  • Landings
  • Living Room
  • Kitchen

How do Flame Detectors Work? 

  • The Flame Detectors work by using Ultraviolet (UV) or infrared (IR) technology to identify flames in less than a second.
  • Flame detectors are built with specialized sensors that sense the presence of flames of specific wavelengths of light radiated by fires.

What is gas detectors used for?

Gas detectors can be used to detect 

  1. Combustible, 
  2. Flammable and Toxic Gases, 
  3. Oxygen Depletion

Are there combination detectors available? 

Yes, Combination detectors include ionization or photoelectric technologiesand carbon monoxide detection to safeguard against both smoke and CO.

Do fire detectors require regular maintenance? 

Yes, fire detectors require regular maintenance with intervals of six months or quarterly.

Can fire detectors be interconnected? 

Yes, fire detectors are interconnected in 2 ways wired and wireless.

Are there specialized fire detectors for specific environments, like industrial settings? 

Yes, there is specialized fire detection systems designed to cater to the unique needs of various industries, like 

  • Manufacturing, 
  • Healthcare, 
  • Hospitality.

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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