What You Need to Know Before Using a Fire Extinguisher

When a fire occurs, you should have the tools and knowledge to put it out. The best way to do that is by using a fire extinguisher, but there are a few things you need to know before you do so.

A fire extinguisher is a sturdy metal cylinder that holds water or a smothering material under high pressure. When you depress a lever at the top, it releases the material through a nozzle into the fire. Fire extinguishers come in a variety of sizes and types, but they all work the same. They can be used to put out Class A fires (wood, paper, and cloth), Class B fires, and Class C electrical fires. Some can even be used on Class D fires (metal).

There are two main types of hand-held fire extinguishers: dry chemical and wet chemical. The dry chemical type contains a pressurized, chemical agent such as sodium bicarbonate, ammonium dihydrogen phosphate, or potassium chloride. It is used to combat class A and class B fires by displacing the oxygen needed for combustion, which suffocates the flames. Carbon dioxide and halon gases are also effective for class A and class B fires, but they are not as easily available as dry chemicals.

A wet chemical fire extinguisher contains a liquid solution of an alkali salt in water under pressure that, when operated, produces a fine mist that cools the fire by soaking the materials and absorbing the heat. They are generally used on Class B and electrical fires, as well as class F fires involving cooking oil and fats.

They can be the most difficult to maintain, and some are not appropriate for flammable solids such as rubber or plastic. They can be used on class A and class B fires, but are not designed to extinguish energized electrical equipment such as computers.

These fire extinguishers are typically blue/red in color and use either aspirated or nonaspirated foam to create a blanket or seal over the fuel, preventing it from contact with air and thus eliminating the chain reaction that ignites the fire. Unlike powder, foam can be used on combustible solids as well as liquids. It can also be used to stop the flow of a liquid fire by blocking the hose and valves.