Fuels

Not all fires are the same, and they are classified according to the type of fuel that is burning. If you use the wrong type of fire extinguisher on the wrong class of fire, you can, in fact, make matters worse. It is therefore very important to understand the four different fire classifications.

     

 

 

 

 

  
Class A - Wood, paper, cloth, trash, plastics
Solid combustible materials that are not metals.
 
 
Class B - Flammable liquids: gasoline, oil, grease, acetone
Any non-metal in a liquid state, on fire. This classification also includes flammable gases.
 
 
Class CClass C - Electrical: energized electrical equipment
As long as it's "plugged in," it would be considered a class C fire.
 
 
Class D - Metals: potassium, sodium, aluminum, magnesium
Unless you work in a laboratory or in an industry that uses these materials, it is unlikely you'll have to deal with a Class D fire. It takes special extinguishing agents (Metal-X, foam) to fight such a fire.
Most fire extinguishers will have a pictograph label telling you which classifications of fire the extinguisher is designed to fight. For example, a simple water extinguisher might have a label like the one below, indicating that it should only be used on Class A fires.