Selecting the Correct Fire Extinguisher

Fire ExtinguisherVirtually all fires are small at first and might easily be contained if the correct type of extinguisher is readily available and properly used. Fire extinguishers are the first line of defense against unfriendly fires and should be installed in all homes and businesses. Selecting the correct extinguisher is important both to insure suitability for the expected type of fire, and to reduce damage to valuables from extinguishing agents. Using the wrong type of extinguisher can needlessly ruin your expensive computer which gets blasted with over spray from a small fire in your office.

Selecting a Fire Extinguisher: Extinguishers are classified according to the type of fire for which they are suitable. The four basic classes are A, B, C and D.

  • Class A: Ordinary combustibles such as wood, paper, cloth and most plastics.
  • Class B: Flammable liquids and gases such as gasoline, oils, paint, lacquers and greases.
  • Class C: Energized electrical equipment where nonconductivity of the extinguishing agent is important.
  • Class D: Combustible metals such as magnesium or titanium. (highly specialized, will not be covered here)

Extinguishers also have a numerical rating which serves as a guide to the amount of fire the extinguisher will handle. The minimum rating for a Class A extinguisher on light hazards is 2A. For Class B or C hazards a rating of 10 is the minimum size recommended. Extinguishers which can handle several types of fires have combined ratings such as 2A:10BC.

Extinguishing Agents: There are five common groups of extinguishing agents. Choose one which will handle the correct class of fire while keeping damage at a minimum.

  • Dry Chemical, standard type: Useful on Class B and C fires. Leaves a mildly corrosive residue which must be cleaned up immediately to prevent damage to electrical equipment. Best uses are automotive, grease fires and flammable liquids.
  • Dry Chemical, multipurpose type: Useful for Class A, B and C fires. Versatile and effective on most common types of fires. Highly corrosive and leaves a sticky residue. Not for use around delicate electrical appliances or computers.
  • Halogenated Agents: Useful on Class A, B and C fires depending on agent used, check label. Expensive but very versatile and clean. Leaves no residue. Mildly toxic. Excellent for delicate computers and electrical equipment. Also good for flammable liquids and automotive use. This is one of the best all around choices for offices, however, environmental restrictions and rising costs limit availability.
  • Carbon Dioxide: Useful on Class B and C fires. Very clean, no residue. Short range, must be applied close to fire.
  • Water Based Agent: Use on Class A fires only. Inexpensive to refill and maintain.

These are the most common extinguishers in use. Base your selection on the size and classification needed plus compatibility with what you are trying to protect. It is also necessary to familiarize yourself with the location, use and limitations of your fire extinguishers. Extinguishers which are required by the Fire Code must be serviced each year.

If an extinguisher is used, don't forget that you still need to call the Fire Department and evacuate the area. Don't put yourself in a dangerous situation. Even if you do put out the fire, call us anyway. We will check to make sure that the fire is completely out. A small fire which appears to be out may actually be burning unseen inside a wall. It can travel up to the attic and turn into a blazing inferno with surprising speed.