Fire extinguishers work by removing one of the elements of the fire triangle: heat, fuel or oxygen. They are labeled according to the type of fire they can put out: Class A for ordinary combustibles like wood; Class B for flammable liquids; or Class C for energized electrical equipment. To properly use an extinguisher, users should remember the PASS method: Pull the pin, Aim at the base of the fire, Squeeze the handle, and Sweep from side to side until the fire is completely out.