Note: Multipurpose (ABC-rated) chemical extinguishers leave a residue that can harm sensitive equipment, such as computers and other electronic equipment. Because of this, carbon dioxide or halon extinguishers are preferred in these instances because they leave very little residue.
ABC dry powder residue is mildly corrosive to many metals. For example, residue left over from the use of an ABC dry powder extinguisher in the same room with a piano can seriously corrode piano wires. Carbon dioxide or halon extinguishers are provided for most labs and computer areas on campuses.
How to Identify the Proper Fire Extinguisher
All ratings are shown on the extinguisher faceplate. Some extinguishers are marked with multiple ratings such as AB, BC and ABC. These extinguishers are capable of putting out more than 1 class of fire.
- Class A and B extinguishers carry a numerical rating that indicates how large a fire an experienced person can safely put out with that extinguisher.
- Class C extinguishers have only a letter rating to indicate that the extinguishing agent will not conduct electrical current. Class C extinguishers must also carry a Class A or B rating.
- Class D extinguishers carry only a letter rating indicating their effectiveness on certain amounts of specific metals.
When using a fire extinguisher, remember the acronym, "P.A.S.S." - Point, Aim, Squeeze, and Sweep.
Remember, leave the area immediately and call 911 if:
- Your path of escape be threatened
- The extinguisher runs out of agent
- The extinguisher proves to be ineffective
- You are no longer be able to safely fight the fire