Classification of Fire Extinguishers

A fire extinguisher is a hand-held device that can be used to fight small fires that could otherwise spread rapidly. Fire extinguishers are available in many sizes and have different ratings for the classes of fires they can be used on. The most important thing to remember when using a fire extinguisher is the acronym PASS, which stands for Pull, Aim, Squeeze and Sweep. The most effective way to use a fire extinguisher is to keep it aimed low and sweep from side to side until the fire goes out. Then be ready to repeat the process if the fire re-ignites.

Class A – Ordinary Combustibles

Right for fires involving wood, paper, cloth and most plastics. Class A fires are not as dangerous to people as other types of fires.

Class B – Flammable Liquids and Gases

Class B fires involve flammable liquids and gases, such as gasoline, kerosene, oil and grease. These fires can be very dangerous due to the chemical reactions they produce. Class B fires can also cause electrical damage, which makes them more difficult to put out than other types of fire.

Classes C – Combustible Metals

Class C fires involve combustible metals, such as magnesium, potassium and sodium. These fires are very deadly and require a very special type of fire extinguisher to douse them. They are usually found in labs and on equipment like generators and power tools.

These extinguishers contain a mixture of copper and sodium chloride that forms a powder that smothers the fire by depriving it of oxygen. These extinguishers are not very effective on class A fires, but they can be useful on class B and class C fires.

There are a number of hand-held fire extinguishers that are designed to handle electrical fires. These typically have a nozzle that discharges an electrically charged spray of water. These extinguishers are extremely effective on class B and class C fires but they can be messy to use.

Often, these extinguishers are placed near electrical equipment to protect against possible electrocution as well as to prevent water from accidentally shorting out circuits or wiring. They are generally rated UL 1496, which means they have been tested for resistance to electrical shock and a minimum of 150 volts.

These types of fire extinguishers are similar to the dry chemical and Halon extinguishers, except that they use a nonflammable carbon dioxide cartridge instead of nitrogen. The CO2 cylinder is a hard-horned cylinder and comes in sizes ranging from 5 to 100 lbs. Unlike other types of fire extinguishers, this type can be used on both Class A and class B fires.

To operate a hand-held CO2 extinguisher, you must first pull the pin that unlocks the operating lever and remove the top handle or lever. Then, aim low and point the nozzle or hose at the base of the fire. Then squeeze the lever or handle and sweep from side to side until the fire is extinguished. You may need to do this multiple times until the fire is completely out and has no re-ignition.