Characterizing Powder Behavior of Dry Chemical Fire Extinguishers for Quality Control and R&D

Dry chemical fire extinguishers using powders as an extinguishing agent are the most common types of handheld fire extinguishers. The requirements for the powders are complex, as many different flow properties must be considered. The powders must have a good dispensability in air to extinguish fires, have relatively fast deaeration times, should ideally be easy to transport and have a low tendency to cake. Understanding the behavior of these powders is important for the development of new formulations and crucial for quality control in production.

Fire extinguishers are fire protection devices for the extinction or control of fires. In order to be able to handle different classes of fires (e.g. flammable liquids or flammable gases) it was necessary to develop different kinds of fire extinguishers, adapted to specific needs. The 1950s saw the development of dry chemical (or powder) fire extinguishers which can be used for many different classes and are comparatively easy to handle and store. The advantages of this technology resulted in powder being the most common type of filling substance in handheld fire extinguishers. Dry chemicals or powders are used as fire extinguishing agents for a wide range of fire classes (A to D). The powders generally consist of a main constituent and additives. A wide range of chemical compounds is used as the main component (for example ammonium sulfate or monoammonium phosphate). The additives are generally used to improve flowability and hydrophobicity. Various powder properties must be controlled in order to ensure proper functioning of fire extinguishers.

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