Inspection Course

Fire Extinguishers

Class Ratings:

Class A ratings:  1A - 40A. For a 1A rating, 1-1/4 gallons of water is required.  A 2-1/2 gallon water extinguisher is rated at 2A.  Therefore, a dry chemical extinguisher rated at 10A is equivalent to five 2-1/2 gallon water extinguishers.

Class B ratings:  1B - 640B. This rating is based on burning flammable liquid n-heptane in square steel pans.  The rating is determined from the approximate square foot area of a flammable liquid fire that a non-expert can extinguish.

Class C ratings:  This is only to assure electrical non-conductivity.

Class D ratings:  No specific test given.  Factors considered; reactions, toxicity of agent, fumes produced, etc.


Presently extinguishers are labelled with pictographs to show what class of fire they can be used on.  Previously, colored geometric shapes were used.

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INDEX Fire Extinguishers

FPT 102 - Fire Prevention and Inspection // Instructor: Kevin M. Kolb        Slide #2