Dry chemical extinguishing
Introduction
Monoammonium phosphate, ABC dry chemical, ABC powder, Tri-class dry chemical or Multi-purpose dry chemical is a dry chemical extinguishing agent used on Class A, Class B and Class C fires. It uses a specially fluidized and siliconized monoammonium phosphate-based powder.[1] ABC dry chemical is usually a mixture of monoammonium phosphate and ammonium sulfate, the former being the active one. The mixture between the two agents is usually 40 to 60%, 60 to 40% or 90 to 10%, depending on local standards around the world. The USGS uses a similar mixture, called Phos Chek G75F.[2].
Uses
Common use
Dry chemical powder used in all types of fires. Stops the chain reaction by suffocating. The pressure may be contained in the extinguisher itself or is generated by gas cartridges stored within the cylinder. Its strength will last 30 seconds and can reach 3 to 5 m.[3][1].
Common combustible solids
Insulates Class A fires by melting at approximately 170–200°C. Class A fires are caused by the burning of common combustible materials, such as wood, paper, or most plastics.[4].
Burning of liquids and gases
The powder breaks the chain reaction of liquid and gas fires by coating the surface to which it is applied. These fires (Class B in the American system; Classes B and C in the European and Australian systems) include the burning of gasoline, petroleum, propane and natural gas.[1] Ideal for oily liquid fires that cannot be extinguished with water.
electrical fires
It is safe and effective for electrical fires since it is not a conductor of electricity. Fires involving live electrical equipment (Class C in the US system; Class E in the Australian system) must be extinguished with equipment that does not conduct its energy back to the user as is the case with water. Electricity can also cause fires of other kinds.[1].