Fire Detectors types and selection
Source: http://www.vedard.com/post-fire-detector.html
Date: 2017/01/27
There are many types of fire detectors. These detectors can predict fire from change of environment. Different situation can induce fire with different cause. So, the change of environment is different as well. Fire detectors are designed to sense defined environment change such as heat, smoke. So, it is required to select different fire detectors for different situation.
Smoke Detectors
Smoke Detector is suitable for situation of much smoke, little heat and flame produced at initial stage of fire. The following properties should use spot-type smoke detectors.
Restaurants, hotels, school buildings, office hall, bedroom, office, etc.
Computer room, communications room, a movie or television show room
Stairs, walkways, elevator machine room, etc.
Library, archives, etc.
The place where there is with danger of electrical fire
TYPES OF SMOKE DETECTORS
There are two types of smoke detectors. They are photoelectric smoke detector and ionization smoke detector. Generally, photoelectric smoke detector is popularlly used cause of no Radiation hazard compared to ionization smoke detector. But these two types smoke detector working effect is different at different situation. So, there is the rule to select the correct type smoke detector.
Where the ionization smoke detector is not suitable
Relative humidity is often greater than 95%
Airflow velocity is greater than 5m/s
There is a large amount of dust, water mist retention
Corrosive gases may be produced
Under normal circumstances there is smoke retention
Alcohols, ethers, ketones etc. organic substances is produced
Where the photoelectric smoke detector is not suitable
Black smoke may be produced
There is a large amount of dust, water mist retention
Steam and oil mist may be produced
Under normal circumstances there is smoke retention
Heat Detector
Heat Detector is suitable for situation of rapid developing fire where a lot of heat is produced. The following properties should use heat detectors.
Relative humidity is often greater than 95%
Smokeless fire
There is a lot of dust
Under normal circumstances there is smoke and steam retention
Kitchen, boiler room, generator room, drying workshop, etc.
Smoking room, etc.
Other places such as halls and public places where smoke detector is not suitable for installation
Flame Detector
Flame Detector is suitable for situation of rapid developing fire where strong flame radiation is produced and with few smoke, heat. The following properties should use flame detectors.
In the fire, there is a strong flame radiation.
Liquid burning without Smoldering stage of fire
Need to react quickly to the fire
Where the flame detector is not suitable
Flameless fire may occur
Smoke spread before the fire
The detector lens is easy to be contaminated
The detector's line of sight is easy to be blocked.
Detectors are subject to direct or indirect exposure to sunlight or other light sources.
There are fire operations and X-ray, arc and other effects in normal circumstances
Combustible gas detector
Combustible gas detectors shall be selected for the situation where flammable gas or liquid vapor is used, produced or accumulated. The following properties should use flame detectors.
Where Pipeline gas or natural gas, LPG is used
Gas station and gas meter housing and storage of liquefied petroleum gas tank place
Other places where combustible gases or vapors may be spreaded
CO detector should be used at where carbon monoxide may be produced
Combination of smoke detector, heat detector, flame detector (same or different types) should be used at places where single detector can not effectively recognize the fire. For fire alarm system with linkage control device, automatic fire extinguishing system, the combination of different types fire detectors should be used as well.
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