Fire extinguishers have a number of different markings on them which are necessary for how they should be used, what types of fires they should be used on and what class of extinguisher they are. Knowing how to identify these markings may be the difference between successfully using a fire extinguisher and putting out a fire or not.
Class A Extinguishers
Class A fire extinguishers are used on fires with ordinary combustibles like wood, cloth and paper. These extinguishers have a clearly marked letter A on them, often with the words "ordinary combustibles" on them. There will also be graphics of a burning trashcan, which means they can be used on ordinary trash fires. There may also be graphics of a gasoline can burning and an electrical outlet burning, but with lines through them, signifying the extinguisher can't be used on fuel or electrical fires.
Class B Extinguishers
Class B extinguishers are used for fires involving liquids, greases or gases. They can also put out the same types of fires class A fire extinguishers can put out. They will have a letter B on them and often have the words "flammable liquids" above and below the letter. They will also have a burning trash graphic and a fuel can on fire graphic, signifying they can put out both trash and liquid fires. However, the burning electrical socket will still have a line through it, showing they can't put out electrical fires.
Class C Extinguishers
Class C fire extinguishers are for electrical fires. They are signified with a letter C with the words "electrical equipment" around them. These extinguishers can put out either fuel fires or electrical fires, and some of these extinguishers can even put out trash fires, making them useful for just about any type of fire which may occur in a home, classroom or office.
Class D Extinguishers
Class D extinguishers are meant to put out fires caused by combustible or liquid metals and are very specialized extinguishers. They are marked by the letter D in a star shape with the words "combustible metals" around it. The faceplate of the extinguisher will also let you know which types of metals it works best on specifically.