Tenant Handbook

Fire Extinguisher Operation

Class A, Class B, and Class C Fires are all Multipurpose Dry Chemical Extinguishers

Fire extinguishers of this type contain an ammonium phosphate base agent. Hand fire extinguishers are available with fire extinguishments ratings of 1-A to 20-A and 10-B: C to 120-B: C and wheeled models with fire extinguishments ratings of 20-A to 40-A and 60-B: C to 320-B:C. Multipurpose agents are used in exactly the same manner as ordinary dry chemical agents on Class B fires. For use on Class A fires, the multipurpose agent has the additional characteristic of softening and sticking when in contact with hot surfaces. In this way, it can adhere to burning materials and fonn a coating that will smother and isolate the fuel from air. When applying the agent, it is important to try to coat all burning areas in order to eliminate or minimize the number of small embers that could be a potential source of reigniting.  The agent itself has little cooling effect and, because of its surface coating characteristic, it cannot penetrate below the burning surface. For this reason extinguishments of deep-seated fires could possibly not be accomplished unless the agent is discharged below the surface or the material is broken apart and spread out.

Fire extinguishers with a Class B rating can extinguish a fire involving combustible cooking media (vegetable or animal oils and fats). Only fire extinguishers having a Class K rating are recommended for use on cooking grease fires.