Fire Extinguisher
Fire extinguisher is basically a fire protection device that is used to extinguish or control fire in emergency situations. The use of fire extinguishers is a very common method for controlling fire. It typically contains a metal cylinder and a small nozzle attached to it and consists of a pressure vessel containing an agent that when discharged from the cylinder can extinguish fire. The agent that is used in fire extinguishers is basically a fire fighting agent that can be discharged under pressure. These fire extinguishers are generally used in case of emergencies when there is no other option available to control the fire but Firefighters should be called when there is any possibility that the fire cannot be controlled within a few seconds. A fire at its beginning is easy to extinguish and therefore fire extinguishers are used for that purpose.
A fire extinguisher may emit a solid, liquid or a gaseous chemical. There are six different types of fire extinguishers that are used in fire hazards but their selection as which one is to be used at what time depends totally upon the type of fire. There are four types of fires:
- Fire through ordinary combustibles such as paper, wood etc.
- Flammable liquids such as gasoline, petrol.
- Electrical fires.
- Burning reactive metal such as sodium, magnesium, titanium etc.
Water is considered as the most common and effective chemical in the case of fire through any combustible substance. A pressurized water extinguisher works by removing heat. It cools the fuel surface and thereby reducing the pyrolysis rate of the fuel. Most water based fire extinguishers also contain traces of other chemicals to prevent the extinguisher rusting. This fire extinguisher cannot be used for Type B fires because burning organic liquids will float on water while continuing to burn.
Another type of fire extinguisher is the high pressure carbon dioxide extinguisher that works by suffocating the fire. Carbon dioxide can be used on electrical fires because as it is a gas therefore it does not leave any residues behind which might further harm the damaged equipments. Carbon dioxide extinguishers have a horn on the end of the hose. Due to the extreme cold of the carbon dioxide that is expelled from an extinguisher, it should not be touched. Halons are very versatile fire extinguishers and are highly effective even at quite low concentrations. This fire extinguisher normally conatins agas that is much heavier than CO2. The gas which is present in Halons extinguisher chemically reacts in a way that shuts down combustion. They are suitable for fires that are due to electrical wires etc.
Another type of fire extinguisher is Dry-chemical extinguisher which is filled with either sodium bicarbonate or potassium bicarbonate. Consequently, they are often used in conjunction with foam for attacking fires by flammable liquids such as gasoline and petrol. They are normally red with small nozzles. The major importance is given in the selection of these fire extinguishers and one should carefully choose that which is suitable for which type of fire.