Mechanism Analysis of Monnex Fire Extinguishing Performance and Particular Burning Fragmentation Phenomenon

Monnex has become the most efficient dry powder extinguishing agent due to its unique fire extinguishing mechanism—the “burning fragmentation” phenomenon. To study the fire extinguishing mechanism of Monnex in detail and elucidate the process of its “burning fragmentation” phenomenon, we have examined the microstructure changes and compositions of Monnex powder during its thermal decomposition process. The results indicate that Monnex undergoes complex iterative reactions and produces explosive intermediates (NH4NO3, KCN, and KN3) when entering the fire. Upon reaching the temperature of 240 °C, the explosive substance is completely pyrolyzed and undergoes a mini- burning fragmentation, resulting in the decomposition of Monnex powder into particles and the release of a large amount of inert gases and free radicals. This is the reason why Monnex has become an optimal dry powder. Toxic substances KCN and KOCN were found during the whole pyrolysis process, so personal protection should be paid attention to in practical applications. Our research not only improves the understanding of the Monnex fire extinguisher, but also provides important scientific evidence for the development of fire extinguishing technologies and environmentally friendly fire protection materials.