Extinguishers

FIRE EXTINGUISHERS

When to use them - how to use them

     Several types of fire extinguishers have been invented to put out different kinds of fires. They must be ready for instant use when fire breaks out. Most portable kinds operate for less than a minute, so they are useful only on small fires. Instructions on the extinguishers tell how to use them most effectively. It is important for the user to learn the properties and proper use of each type for each class of fire. The law requires ships, trains, intercity buses, and airplanes to carry extinguishers. They hang in schools, theaters, factories, stores, and high-rise buildings. Some people keep them in their homes, in barns, and in automobiles.
Extinguishers

   The principle on which extinguishers work is based on the nature of fire. When a flammable substance is heated to a certain temperature, called the ignition point, or kindling temperature, the substance combines with oxygen from the air and bursts into flame. Usually the fire raises the temperature of adjoining substances to their ignition points. Then the blaze spreads.

   Since fuel, oxygen, and heat must be present in order to have fire, one or more of these three elements must be removed or reduced to extinguish a fire. If the heat is reduced by cooling the substance below the kindling temperature, the fire goes out. The cooling method is the most common way to put out a fire. Water is the best cooling agent because it is low in cost and usually readily available in quantity.

   Another method of extinguishing fire is by eliminating or diluting the oxygen. This is usually done by smothering or blanketing the fire. Some substance that is not readily combustible is used to cover the fire. Sand, foam, steam, or a nonflammable chemical may be employed. A blanket or rug may be used to cover and smother a small blaze.

   A third method is called separation. This method involves removing the fuel, of combustible material, from a fire. In forest fires, for instance, the trees may be cut away leaving a fire lane in which the spreading flame can find no fuel. Explosives may be employed to block oil-well fires.


Three Classes of Fires

The method that is used to put out a fire depends upon the type of fire. Fires have been grouped in four classes.
Class A
Fires in wood, paper, cloth, and similar common materials are called Class A fires. These materials usually form glowing coals, which help to sustain the fire. Such fires can be stopped most readily by cooling with water or watery solutions. Water has the advantage of usually being plentiful and cheap.
Class B
Blazes in flammable liquids such as gasoline, oil, or grease are termed Class B fires.. The material and the fire would float and spread if a stream of water were used on the flames. Such blazes are smothered; that is, oxygen from the air is cut off.
Class C
fires those in charged electrical equipment should be put out by an agent which does not conduct electricity.
Class D
Certain combustible metals, such as magnesium, titanium, potassium and sodium. These metals burn at high temperatures and give off sufficient oxygen to support combustion. They may react violently with water or other chemicals, and must be handled with care.


Types of Fire Extinguishers

   The simplest extinguisher contains water and has a hand pump to throw a stream. A garden hose can serve the same purpose. A common chemical type is the soda-acid extinguisher. It contains bicarbonate of soda dissolved in water and a small container of sulfuric acid. When the extinguisher is inverted, the chemicals mix and generate carbon dioxide (CO2). This gas forces the fluid through a hose.

   Foam extinguishers are used in flammable-liquid Class B fires as well as Class A fires. Solutions of sodium bicarbonate and aluminum sulfate in separate compartments mix when the extinguisher is inverted. The resulting foamy mixture floats on the burning liquid, smothering the flames.

   A smothering and cooling extinguisher consists of a steel cylinder of carbon dioxide under high pressure. When released the heavy gas forms a blanket over a liquid fire. Continued use prevents reflashing. It is also used on Class C blazes.

   Extinguish combustible metals such as magnesium, titanium, potassium and sodium with dry powder extinguishing agents specially designated for the material involved. In most cases, they absorb the heat from the material, cooling it below its ignition temperature. In some cases, covering the burning metal with sand can help contain the heat and sparks from the reaction. Class D exinguishing agents are available (generally as a dry powder in a bucket or box) which can be quite effective, but these agents are rare on the campus.

   In dry-chemical extinguishers a cartridge of high-pressure gas is released. It blows a powdery coating of sodium bicarbonate over flaming liquids, electrical equipment, or other materials. Vaporizing-liquid extinguishers contain a fluid which will be vaporized into a smothering gas by the heat of the fire. Care should be taken not to breathe the fumes.

   Extinguishers should be inspected and recharged regularly. Reliable ones bear the approval label of a recognized testing laboratory.


Where To Use

   It is natural for a person to use the extinguisher located nearest to a fire which makes it essential that the correct type and size be placed in close proximity to a potential hazard. The most current issue of NFPA-10 should be consulted for minimum recommended fire extinguisher types, placement and travel distances. Your local extinguisher distributor is professionally qualified and equipped to help you evaluate and implement these recommendations. Or your local Fire Department can assist you.

   All new fire extinguisher nameplates have the USE symbols shown (older extinguishers will have A B C letters or combinations of these letters). Anyone who might be expected to use a fire extinguisher should be familiar with the USE symbols which identify the classes of fire on which it may be used. The International Sign System red slash, if present, indicates a potential hazard to the user if the extinguisher is used on that particular class of fire. Absence of a class symbol simply means that the extinguisher is not recommended as particularly effective for that class.


How To Use
Remember the PASS-word!
Keep your back to an unobstructed exit and stand six to eight feet away from the fire. Follow the four-step procedure: Pull, Aim, Squeeze, and Sweep.
Pull the Pin: This unlocks the operating lever and allows you to discharge the extinguisher. Some extinguishers may have other lever-release mechanisms.
AIM low: Point the extinguisher nozzle ( or hose ) at the base ( bottom ) of the fire
SQUEEZE the lever above the handle:This discharges the extinguishing agent. Releasing the lever will stop the discharge. (Some extinguishers have a button instead of a lever)
SWEEP from side to side: Moving carefully toward the fire, keep the extinguisher aimed at the base of the fire and sweep back and forth until the flames appear to be out. Watch the fire area. If the fire re-ignites, repeat the process.
Always be sure that the fire department is called to check the fire site, even if you think you've extinguished the fire

WHEN NOT TO FIGHT A FIRE

Never fight a fire:

In any of these situations,

DON'T FIGHT THE FIRE YOURSELF.
CALL FOR HELP.


   All extinguishers should comply with the recommendations of the National Fire Protection Association (NFPA) and be tested and rated by Underwriters Laboratories and/or Factory Mutual Systems to ANSI/UL specifications. In compliance with National and Local OSHA requirements


Installation and Maintenance

   Extinguishers should be installed in plain view, above the reach of children, near escape route, and away from stoves and heating appliances.

   Extinguishers require routine care. Read your operator's manual to learn how to inspect your extinguisher. Follow manufactures instructions for maintenance.
   Rechargeable models must be serviced after every use. (Service companies are listed in the yellow pages under "Fire Extinguishers,") Disposable fire extinguishers can be used only once and must be replaced after they are used.


Should You Fight the Fire?

Before you begin to fight a fire, make sure that:

   It is reckless to fight a fire in any other circumstances. Instead, leave immediately and close ( all doors and/or windows) off the area.
   For more information on the selection and use of portable fire extinguishers, see NFPA (National Fire Protection Association) publication BKLT-2: Portable Fire Extinguishers: Fighting Small Fires.


National Fire Protection Association

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