The dry powder fire extinguisher is filled with ammonium phosphate dry powder fire extinguishing agent. Dry powder fire extinguishing agent is a dry and easily flowing fine powder used for fire extinguishing. It is composed of inorganic salt with fire extinguishing effect and a small amount of additives which are dried, crushed and mixed into fine solid powder. It is a fire extinguishing agent widely used in fire fighting, and is mainly used in fire extinguishers.

Due to its large specific surface area and high activity, ultrafine fire extinguishing particles can be suspended in the air for several minutes to form relatively stable aerosols. Therefore, not only the fire extinguishing efficiency is very high, but also the use method is completely different from the general traditional dry powder fire extinguishing agent, which is similar to the haloalkane flooding fire extinguishing. For example, the extinguishing concentration of KHCO3 aerosol is only 2.0% of 1301 halogenated alkane, but its extinguishing efficiency is 50 times that of it, and the sediment after extinguishing is not obvious, causing little pollution to the fire site. KHCO3, NaCl, KCl, K2SO4, NH4H2PO4 and NaHCO3 can be used to prepare aerosol fire extinguishing agent. The particle size of aerosol fire extinguishing agent shall be less than<5 μ m. Better less than 0.5 μ m. Aerosol has become an independent new research field.