С. 2. Translate the text FIRE WARNING DEVICES and then discuss it with your partner

Date: 2015-10-07; view: 463.

Early fire warning devices play an important role in reducing the like­lihood of injury to people from fires. Two different types of early warning systems are on the market today. One is a smoke detector, and the other, a sensory detector. Smoke detectors work on the principle that shortly after a blaze ignites, smoke from the fire can be detected and an early warning signal given. Since most fatalities from a fire result from smoke inhalation and be­cause smoke spreads faster than heat, a smoke detector can give a warning before the smoke has built up to a dangerous level.

There are two kinds of smoke detectors: the photoelectric detector and the ion chamber detector. The photoelectric detector senses a smol­dering fire more quickly than it does a flaming fire. The ion chamber detector operates on a slightly different prin­ciple. Key components are two inner chambers and a radioactive source. Rays from the source flow into the sensing chamber, and any particle entering the chamber changes the balance of voltage and trig­gers the alarm. This type of detector is more sensitive than the photoelectric detector.

A second type of early warning fire detection makes use of heat sensing. The heat sensor activates an alarm system when a certain temperature level is reached. This system will indicate when a fire is burning in the area where the sensor is located. In most hotels and motels, theaters, and other buildings where large crowds gather, it is mandatory that there be automatic sprinkler systems.

The most commonly found sprinkler system is the wet pipe system. In this system the pipes are full of water under pressure. The sprinkler head is activated by a small heat detector and water is dis­charged. In areas where freezing pipes can be a problem, a dry pipe system is employed. With this system the pipes are filled with dry com­pressed air.