Fire Extinguishing Efficiency of Magnesium Hydroxide Powders under Different Particle Size

Abstract

After Montreal protocol, more and more new materials have been applied as the substitutes of Halon. Much attention has been paid to fire extinguishing efficiency of alkali metal salts and ammonium phosphate salts, but the effects of particle sizes have not been studied sufficiently. The fire-extinguishing efficiency of a new kind of agent based on magnesium hydroxide of different particle size was studied in this paper. Four different size powders have been used to study their fire-suppression efficiency through laboratory scale experiments in a confine space of 1*1*1m. The physical and chemical characteristics of the magnesium hydroxide powders were characterized by scanning electron microscopy (SEM) and thermal gravity analysis (TGA). The results have exhibited that these four kinds of powders are all high efficient for the fire suppression efficiency and there is a threshold value of 5μm for the fire suppression efficiency of magnesium hydroxide. The efficiency can be affected by the morphology of powders and particle size. The powders of larger specific surface area and smaller particle size are more efficient to suppress fire. Fire extinguishing and possible fire-suppression mechanisms have also been analyzed from three aspects: chemical inhibition, cooling effect and asphyxiation effect.