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Portable Fire Extinguishers1. The sooner a fire is detected, the easier it is to put out. 2. Most home fires occur at night when the family is asleep. 3. Fire departments advise people to install smoke detectors in their homes. 4. Smoke detectors sound an alarm if a small amount of smoke enters their sensors. 5. The most commonly used fire extinguishing devices are portable fire extinguishers. 6. Portable fire extinguishers are an item of firefighting equipment containing a fire extinguishing medium. 7. Their advantages are their simplicity in operation and design. 8. Their disadvantages are that they must be operated manually. 9. Portable fire extinguishers can be classified according to the extinguishing agent they contain and according to their method of operation. 10. According to the extinguishing agent portable fire extinguishers can be divided into 5 categories. 11. A fire extinguisher consists of several basic components. 12. The first is a container with extinguishing agent. In the small, first-aid water fire extinguishers, a propellant must be provided. 13. Usually this is a carbon dioxide.
ADDITIONAL MATERIAL TEXT 1 Early Detection Alarm Systems The five principal types of fire detectors in common use are: 1. Electronic combustion gas detector. This device detects the combustion gases at an early stage of a fire, often long before the smoke would be noticed. Such a detector can usually monitor in excess of 500 ft2 (50 m2 or more) of floor area and is preferred in occupancies where life safety is critical. 2. Radiant-emission detector. Such detector responds to infrared or ultraviolet radiation. In some cases, this detector is designed to respond to rapid fluctuation in the radiation, the rate of fluctuation being chosen to correspond approximately to the flicker rate of fires but to exclude the background radiation from other sources. Some versions have a response delay to further screen out background signals. Such a detector can monitor as much as 1,000 m2 of floor area of its field of view. 3. Light-scattering (or refracting) detector. This device appears in various versions, each employing a different principle. One commonly used detector of this type is based on the scattering of light by smoke particles. A new device uses the reflection of a multiply reflected laser beam to detect convection cells produced by a fire. The smoke detectors are relatively slow, and they sample only small volumes of room area, but the laser-beam approach appears to suffer neither disadvantage. 4. Fixed-temperature detectors. This detector triggers an alarm upon reaching a present temperature. Typical versions respond at a temperature level of 70oC. They are also available in temperatures ranging from as low as 50oC to as high as 130oC. The fixed-temperature detector ordinarily will protect an area of 10 m2. Relatively sluggish in response, this type of detector is unsuited in protection of unoccupied property, such as in automatic sprinkler systems for warehouses and the like. 5. Rate of temperature rise detector. Such a type responds to a quick rise in room temperature. A typical version responds when the rate of rise exceeds about 0,2C/S; first, however, the temperature must exceed a certain fixed value. A rate of temperature detector usually monitors about 20 m2 of floor area. TEXT 2
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