Fire- Types- Extinguishers

 Fire 

Fire is the burning of combustible material. A fire in an unwanted place and on occasion and in an uncontrollable quantity can causes damage or destroy property and materials. It might injury people ad sometimes cause loss of life as well. Hence every effort must be made to prevent fire. When a fire out break is discovered, it must be controlled and extinguished by immediate corrective action.

Is it possible to prevent fire? Yes, fire can be prevented by eliminating anyone of the three factors that causes fire.

The following are the three factor that must be present in combination for a fir to continue to burn.( Fig 1)

    

Fuel: Any substance liquid, solid, or gas will burn, if there is oxygen and high enough temperature.

Heat: Every fuel will begin to burn at certain temperature.It various and depends on the fuel. Solid and liquids give off vapor when heated, and it is this vapor which ignites.Same liquids do not have to be heated as they give off vapor at normal room temperature say 150 degree c, etc  petrol.

Oxygen: Usually exists in sufficient quantity in air to keep a fire burning.

Extinguishing of  fire: Isolating or removing any of these factors from the combination will extinguish the fire .there are three basic ways of achieving this.

• Starving the of fuel removes this element.
• Smothering- ie. isolate the fire from the supply of oxygen by blanketing with foam, sand etc.
• Cooling -  use water to lower the temperature.

Removing

 any one of these factor will extinguisher the fire.

Preventing fires: The majority of the fires begin with small outbreaks which burn unnoticed until they have a secure hold. Most fires cloud be prevented with more care and by following some simple common sense rule.

Accumulation of combustible refuse ( cotton waste soaked with oil, scrap wood, paper,etc) in odd corner are fire risk refuse should be removed to collection point.

The cause of fire in electrical equipment is misuse neglect. loose connection, wrongly rated fuse, overloaded circuits cause overheating which may in turn lead to fir. Damage to insulation between conductors in cables causes fire.

Clothing and any thing else which might catch fire should be kept well away from heaters. Make sure that the heater is shut off at the end of the working day.

highly flammable liquids and petroleum mixtures (thinner, adhesive solutions, solvent, kerosene, sprit, LPG gas etc,) should be stored in the flammable material storage area.

Blowlamps and torches must not be left burning when the are not in use.

Classification of fires:  Fires are classified into four types in terms of the nature of fuel.

Different types of fire ( Fig 2, Fig 2, Fig 3, Fig 4& Fig 5 ) have to be dealt with in different ways extinguish agents.

An extinguishing agent is the material or substance used to put out the fire and is usually
 (but not always) contained in fire extinguisher with a release mechanism for spraying into the fire.

It is important to know the right type of agent for extinguishing a particular type of fire; using a wrong agent can make thing worse. There is no classification for electrical fires as such since these are only fires in materials where electricity is present.

Types of fire Extinguisher

Many types of fire extinguishers are available with different extinguisher "agent" to deal with different classes of fires. ( Fig 1)

 

Water-filled extinguishers: There are two methods of operating.( Fig 2 )

• Gas cartridge type 
• Stored pressure type

With both method of operation the discharge can be interruted as required, conserving the content and preventing unnecessary water damage.

Foam extinguisher ( Fig 3) :These may be of stored pressure or gas cartridge types. Always check the operating instructions on the extinguisher before use.

Most suitable for

• flammable liquid fires
• running liquid fires 

must not be used on fires where electrical equipment is involved.

 

Dry powder extinguishers ( Fig 4): Extinguisher fitted with dry powder may be of the gas cartridge or stored pressure type. Appearance and method of operation is the same as that water-filled  one. The main distinguishing feature in the fork shaped nozzle. Powders have been developed to deal with class D fires.

Carbon dioxide ( CO 2) : This type is easily distinguished by the distinctively shaped discharge horn.( Fig 5)

Suitable for class B fires. Best suited where contamination by deposit must be avoided. Not generally effective in open air.

Always check the operating instruction on the container before use. Available with different gadgets of operation such as - plunger, lever, trigger etc.

Halon extinguisher ( Fig 6) : These extinguisher may be filled with carbon - tetra chloride and Bromochlorodifluoro  methene ( BCF) . They may be either gas cartridge or stored pressure type.

They are more effective in extinguisher small fires involving pouring liquids. These extinguisher are particularly suitable and safe to use on electrical equipment as the chemical are electrically non-conductive.

                   

                   The fumes given off by these extinguisher are 

                   dangerous, especially in confined space.

The general procedure in the event of a fire:

• Raise an alarm

• Turn off all machinery and power ( gas and  electricity 0 

• Close the doors and windows, but do not lock or bolt them. This will limit the oxygen fed to fire an prevent its spreading.

• Try to deal with the fire if you can do so safely. Do not risk getting trapped.

• Anybody not involved in fighting the fire should leave calmly using the emergency exits and go to the designed assembly point.

• Analyze and identify the type of fire.refer Table 1.

Assume the fire is 'B; type (flammable liquifiable solid )

• Select CO2 ( carbon dioxide ) fire extinguisher.
• Locate and pickup, CO2 fire extinguisher. Click for its expairy date.
• Break the seal (Fig 2)

Pull the safety pin from the handle (pin located at the top of the fire extinguisher ) (Fig 3 )

• Aim the extinguisher nozzle or hose at the base of the fire ( this remove the source of fuel fire) (Fig 4 )

                           Keep your self low and safe distance 

• Squeeze the handle lever slowly to discharge the agent ( Fig 5) 
• Sweep side to side approximately 15 cm over the fuel fire until the fire is put off ( Fig 5)  

 Fire extinguishers are manufactures for use from the distance.

Caution

• While putting off fire, the fire may flare up 

• Do not be panic belong as it put of promptly

• If the fire doesn't respond well after you have used up the fire extinguisher move away yourself away from the point.

• Do not attempt to put out a fire where it is emitting toxic smock leave it for the professionals.

• remember that your life is more important than property. So don't yourself or others at risk.

In order to remember the simple operation of the extinguisher. Remember P.A.S.S.This will help you to use the fire extinguisher.
P for Pull 
A for Aim 
S for Squeeze 
S for Sweep