No single fire extinguisher is going to be effective against all types of fires, and 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. Therefore, it is important to know what the different ratings on fire extinguishers mean, and what they are used for.
Types of Fires
There are five 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. For an A rating, the number is an indication of water equivalency, with each A being the same as 1 1/4 gallons of water. Thus, a 4A will equal about five gallons of water. The numbers on a B or C rating will indicate the square footage that extinguisher can handle. 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 two square feet of a Class B fire. There are no numerical ratings for Class D or K extinguishers as they are for very particular uses. Class D types will have a relative effectiveness detailed on the faceplate for the specific type of metal combustible fire it is to be used for.
Most general use 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 or water capacity, but it may also mean that the fire extinguisher is too heavy for a single person to carry. Many newer extinguishers will also be labeled with a picture diagram for a rating, with the illustrations showing their uses instead of just letters.
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.
Be sure that all members of your family know how to use a fire extinguisher in case of emergency.