Abstract: For the sake of improving the extinguishing efficiency of the dry powder, a new type of superfine dry powder was prepared with the magnesium hydroxide as additive. The thermal analysis instruments thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC) were used to study the thermal decomposition processes. Through small-scale fire experiments, physical quantities of the extinguishing processes were obtained for suppressing diesel fires by different powders. The quantities were used to evaluate the extinguishing capability and the suppressing toxic gases ability of different powders. The results show that during the thermal decomposition process, magnesium hydroxide increases the peak decomposition rate of compound superfine powder and reduces the characteristic temperature in each stage, that in the fire-extinguishing process, magnesium hydroxide reduces the dosage of powder, shortens the extinguishing time, decreases the minimum fire extinguishing concentration (MEC), and effectively inhibits the production of toxic and harmful gases.

Key words: compound superfine dry powder extinguishant, magnesium hydroxide, thermal decomposition, extinguishing efficiency, flue gas concentration