Physical Characteristics of Fire-Extinguishing Powders

Powders are known to be highly efficient fire-extinguishing agents. There are powders available that, on both weight and volume bases, are more efficient than Halon 1301 as fire-extinguishing agents. A project was undertaken to examine several powders by both optical microscopy and scanning election microscopy. Much of the information from these two forms of microscopy is complementary. The term 'characteristic dimension' was defined and applied in order to rank the powders on a size basis. Eleven fire-extinguishing powders and two common commercial powders were examined by both forms of microscopy. The fire-extinguishing grade of aluminum oxide had the smallest average characteristic dimension followed by the 'micronized' sodium bicarbonate samples. These sodium bicarbonate powders appeared to have very little agglomeration of the particles. The large amount of drying agent (approximately 8%) may explain this fact. In addition, most of the sodium bicarbonate powders had similar average characteristic dimensions. Therefore, it is felt that they may perform similarly as fire-extinguishing agents.Army Research Lab Aberdeen Proving Ground is the author of 'Physical Characteristics of Fire-Extinguishing Powders', published 1997 under ISBN 9781423581185 and ISBN 1423581180.