Pls give the detail of fire extinguishers with fig.?

I. INTRODUCTION





Modern Fire Extinguisher













Modern Fire Extinguisher

Fire extinguishers for the home or workplace should be rated to control a variety of different types of fires. This heavy-duty model is filled with a dry chemical agent under pressure, while other extinguishers may be filled with foam or carbon dioxide. A squeeze grip and a flexible hose allows a user to aim the extinguishing powder directly at a fire.

Encarta Encyclopedia

Craig Lovell/CorbisCorbis







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Fire Extinguisher, portable device used to put out fires of limited size. Such fires are grouped into four classes, according to the type of material that is burning. Class A fires include those in which ordinary combustibles such as wood, cloth, and paper are burning. Class B fires are those in which flammable liquids, oils, and grease are burning. Class C fires are those involving live electrical equipment. Class D fires involve combustible metals such as magnesium, potassium, and sodium. Each class of fire requires its own type of fire extinguisher.



Standards for the selection, placement, and testing of portable fire extinguishers are issued by the National Fire Protection Association, a nonprofit technical and educational organization in Quincy, Massachusetts. The standards establish the minimum requirements for all types and sizes of extinguishers that are listed and rated by testing laboratories against standard test fires of the types they are designed to control. Each extinguisher is rated as to both type and size of the fire extinguished. For example, a 20-B extinguisher should extinguish a flammable-liquids fire that is 20 times the size of a fire that an extinguisher rated 1-B would extinguish. Extinguishers that cannot extinguish the minimum size test fires are not listed or rated. Some extinguishers will put out only one class of fire; others are used for two or even three classes; none is suitable for all four classes.



Fire extinguishers may go unused for many years, but they must be maintained in a state of readiness. For this reason, periodic inspection and servicing are required, and that responsibility rests with the owner. Fire department inspectors check at periodic intervals to see that extinguishers are present where required by law and that they have been serviced within the specified time period.



II. EXTINGUISHERS FOR CLASS A FIRES



Class A fire extinguishers are usually water based. Water provides a heat-absorbing (cooling) effect on the burning material to extinguish the fire. Stored-pressure extinguishers use air under pressure to expel water. Pump-tank extinguishers are operated by a hand pump.



III. EXTINGUISHERS FOR CLASS B FIRES



Class B fires are put out by excluding air, by slowing down the release of flammable vapors, or by interrupting the chain reaction of the combustion. Three types of extinguishing agents—carbon dioxide gas, dry chemical, and foam—are used for fires involving flammable liquids, greases, and oils. Carbon dioxide is a compressed gas agent that prevents combustion by displacing the oxygen in the air surrounding the fire. The two types of dry chemical extinguishers include one that contains ordinary sodium or potassium bicarbonate, urea potassium bicarbonate, and potassium chloride base agents; the second, multipurpose, type contains an ammonium phosphate base. The multipurpose extinguisher can be used on class A, B, and C fires. Most dry chemical extinguishers use stored pressure to discharge the agent, and the fire is extinguished mainly by the interruption of the combustion chain reaction. Foam extinguishers use an aqueous film forming foam (AFFF) agent that expels a layer of foam when it is discharged through a nozzle. It acts as a barrier to exclude oxygen from the fire.



IV. EXTINGUISHERS FOR CLASS C FIRES



The extinguishing agent in a class C fire extinguisher must be electrically non-conductive. Both carbon dioxide and dry chemicals can be used in electrical fires. An advantage of carbon dioxide is that it leaves no residue after the fire is extinguished. When electrical equipment is not energized, extinguishers for class A or B fires may be used.



V. EXTINGUISHERS FOR CLASS D FIRES



A heat-absorbing extinguishing medium is needed for fires in combustible metals. Also, the extinguishing medium must not react with the burning metal. The extinguishing agents, known as dry powders, cover the burning metal and provide a smothering blanket.



The Underwriters' Laboratories, Inc., has available lists of approved fire extinguishers that may be purchased from different manufacturers. The extinguisher label gives operating instructions and identifies the class, or classes, of fire on which the extinguisher may be used safely. Approved extinguishers also carry the labels of the laboratories at which they were tested.



Microsoft ? Encarta ? 2007. ? 1993-2006 Microsoft Corporation. All rights reserved.



Modern Fire ExtinguisherFire extinguishers for the home or workplace should be rated to control a variety of different types of fires. This heavy-duty model is filled with a dry chemical agent under pressure, while other extinguishers may be filled with foam or carbon dioxide. A squeeze grip and a flexible hose allows a user to aim the extinguishing powder directly at a fire.Craig Lovell/CorbisCorbis

Microsoft ? Encarta ? 2007. ? 1993-2006 Microsoft Corporation. All rights reserved.

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Pls give the detail of fire extinguishers with fig.?
http://home.howstuffworks.com/fire-extin...
Reply:Pl. browse the following sites for a detailed description of fire extinguishers:

www.fireservice.co.uk/safety/extinguis...



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www.safelincs.co.uk/section.php?xSec=3



www.firehouseinternational.com/usersit...
Reply:Choosing Fire Extinguishers

Identify the type of materials in the area



Class A: SOLIDS such as paper, wood, plastic etc

Class B: FLAMMABLE LIQUIDS such as paraffin, petrol, oil etc

Class C: FLAMMABLE GASES such as propane, butane, methane etc

Class D: METALS such as aluminium, magnesium, titanium etc

Class E: Fires involving ELECTRICAL APPARATUS

Class F: Cooking OIL %26amp; FAT etc



Types of fire extinguisher

Water Fire Extinguishers:

The cheapest and most widely used fire extinguisher. Used for Class A fires. Not suitable for Class B (Liquid) fires, or where electricity is involved.



Foam Fire Extinguishers:

More expensive than water, but more versatile. Used for Classes A %26amp; B fires. Foam spray extinguishers are not recommended for fires involving electricity, but are safer than water if inadvertently sprayed onto live electrical apparatus.



Dry Powder Fire Extinguishers:

Often termed the ‘multi-purpose’ extinguisher, as it can be used on classes A, B %26amp; C fires. Best for running liquid fires (Class B). Will efficiently extinguish Class C gas fires, BUT BEWARE, IT CAN BE DANGEROUS TO EXTINGUISH A GAS FIRE WITHOUT FIRST ISOLATING THE GAS SUPPLY. Special powders are available for class D metal fires.



Warning: when used indoors, powder can obscure vision or damage goods and machinery. It is also very messy.



CO2 Fire Extinguishers:

Carbon Dioxide is ideal for fires involving electrical apparatus, and will also extinguish class B liquid fires, but has NO POST FIRE SECURITY and the fire could re-ignite.



Wet chemical

Specialist extinguisher for class F fires.



For Metal Fires: A specialist fire extinguisher for use on Class D fires - metal fires such as sodium, lithium, manganese and aluminium when in the form of swarf or turnings.



Colour Coding



Prior to 1st Jan 1997, the code of practice for fire extinguishers in the UK was BS 5423, which advised the colour coding of fire extinguishers as follows:



Water - Red



Foam - Cream



Dry Powder - Blue



Carbon Dioxide (CO2) - Black



Halon - Green (now 'illegal' except for a few exceptions such as the Police, Armed Services and Aircraft).







http://www.mfs-fire-extinguishers.co.uk/...