Understanding Fire Extinguisher Ratings and Uses

No single fire extinguisher is going to be effective against all types of fires. Using the wrong type of extinguisher can be disastrous. For example, if you use a water-based fire extinguisher on an electric fire, you will end up spreading the fire and exposing yourself to electrocution.

Types of Fires

There are 5 general categories of fires.

• Class A fires are started from ordinary combustible materials such as paper, wood, or trash
• Class B fires are the result of accidents with combustible liquids such as petrol, gasoline, or thinners
• Class C fires are the result of an electric problem or malfunctioning electric equipment
• Class D fires are started by combustible metals such as magnesium or titanium
• Class K fires are generally seen in commercial kitchens, and are the result of accidents involving cooking oils and fats

Fire Extinguisher Ratings

All fire extinguishers have ratings stamped on the faceplate of the appliance. In most cases, the rating is a combination of numbers and letters. The number is an indication of the fire burning capability of the contents in that particular fire extinguisher. The letter indicates the type of fire that the fire extinguisher can be used on. For example, a rating of 2B means that the fire extinguisher can be used to combat 2 square feet of a Class B fire.

Most fire extinguishers have ratings of AB, BC, or ABC. This means that they can be used on more than one type of fire. For general home use, you must have a fire extinguisher with an ABC rating. Most home fires fall in the A, B or C category and sometimes can be a combination of several factors. Keep in mind that a higher rating number means a greater coverage area, but it may also mean that the fire extinguisher is too heavy for a single person to carry.

Emergency planning and training are important aspects of fire safety. When purchasing a fire extinguisher, you must ensure that each grown member of your family can handle it comfortably. For home use, a suitable rating for a fire extinguisher is 2A:10B:C. This type of dry chemical fire extinguisher is generally based on chemicals such as potassium bicarbonate or ammonium phosphate. The number 2 preceding the letter A indicates that the fire extinguisher can equal the extinguishing power of 2 x 1.25 = 2.5 gallons of water. The number 10 preceding the letter B indicates a firefighting capability of up to 10 square feet of fire. The letter C is never preceded with a number. It only indicates that fire extinguisher is safe to use on an electrical fire, and that its contents are not conductors of electricity. A "C" rating on a fire extinguishers is always accompanied by one or more other letters.