Answer:
Fire is one of humankind's oldest discoveries; it's also one of our biggest threats. A fire can destroy in a matter of minutes home or business that has taken decades to establish. That's why methods of putting out fires are so important. Many buildings are equipped with fire extinguishers, but why are there so many different kinds? What do they do to a fire? And how exactly do they work?
Fire extinguishers are helpful because they can save lives and property by putting out a small fire or suppressing it until the fire department arrives. Fire safety experts advise that you attempt to extinguish a fire only if you have first made sure that everyone else has left or is leaving the building, and that someone has called the fire department. Remember, lives are more important than property.
If those conditions have been met, you should pick up the fire extinguisher and attack the fire. Be careful to make sure that at all times your back is to a safe exit. You'll also want to make sure that the fire is confined to one area. If it begins to spread to other areas, such as walls and curtains, you should retreat from the room if there is a chance the fire could surround you.
You also want to beware of smoke. If the room begins to fill to the point that you can't see or breathe, you should retreat.
There are four main types of extinguishers and they work in slightly different ways:
Water extinguishers, which are the most common, are essentially tanks full of water, often with nitrogen or carbon dioxide as the propellant to make them come out. Water extinguishers work mainly by removing heat from the fire, though they also help to cut off a fire's oxygen supply.
Dry powder extinguishers are tanks of dry powder with compressed nitrogen as the propellant. In extinguishers like this, it's the composition of the chemical (rather than the mechanical design of the extinguisher) that really counts The powder is a specially designed mixture that absorbs heat, melts, and coats the fuel, stopping it from making flammable vapors and blocking out oxygen, so it's helping to tackle two sides of the fire triangle at once. The most widely used powder in extinguishers is monoammonium phosphate; other powder ingredients include the metal alkali salts sodium bicarbonate (baking soda) and potassium bicarbonate (similar to sodium bicarbonate), though these are less effective on things like wood and paper fires.
Foam extinguishers are tanks of water and foam with compressed nitrogen as the propellant. They work by smothering the fire: when you spread a thin layer of foam over a fire, you cut the fuel off from the oxygen around it. Foam extinguishers also help to absorb heat, since the cool foam they release contains a lot of water.
Carbon dioxide (CO2) extinguishers contain a mixture of liquid and gaseous carbon dioxide (a nonflammable gas). CO2 is normally a gas at room temperature and pressure. It has to be stored under high pressure to make it a liquid. When you release the pressure, the gas expands enormously and makes a huge white jet. CO2 attacks the fire triangle in two ways: it smothers the oxygen and, when it turns from a liquid back to a gas, it "sucks" in a massive amount of heat from its surroundings (the latent heat of vaporization), which cools whatever you spray it on by removing heat.
how are fire extinguishers helpful?
They are helpful because they can save lives and can help you get out of a sticky situation. The stuff inside the fire extinguishers could be water, water, and foaming agent mixture, dry powder, wet chemical or CO2 gas compressed into a liquid. Propellant – this is what forces the extinguishing agent out of the fire extinguisher. It is often compressed nitrogen gas.