The model indicated by letters on fire extinguishers and their use

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**The standards stipulate that the fire extinguisher model should be marked on the cylinder using uppercase Pinyin letters and Arabic numerals, such as “MF2”. The first letter, M, stands for fire extinguisher, while the second letter indicates the type of extinguishing agent (F refers to dry powder extinguishers, FL to ammonium phosphate dry powder, T to carbon dioxide extinguishers, Y to halon extinguishers, P to foam, QP to light water foam extinguishers, and SQ to water extinguishers). The subsequent Arabic numerals represent the weight or volume of the extinguishing agent, with the unit usually being kilograms or liters. Fires are classified into five categories, and corresponding fire extinguishing equipment should be used. Category 1 refers to fires involving combustible carbonaceous solids, such as wood, cotton, linen, paper, and the like. Water-based fire extinguishers, foam fire extinguishers, dry powder fire extinguishers, halon fire extinguishers can be used ； Category 2 refers to liquids of types A, B, and C; fires caused by the combustion of substances such as gasoline, kerosene, diesel, and methanol can be extinguished using dry powder fire extinguishers, foam fire extinguishers, or halon fire extinguishers ； Category 3 refers to fires caused by flammable gases such as gas, natural gas, methane, etc.; these can be extinguished using dry powder fire extinguishers or halon fire extinguishers. Category 4 refers to fires caused by flammable reactive metals such as potassium, sodium, magnesium, etc.; these can be extinguished using dry sand or cast iron powder ； Category 5 refers to fires caused by burning electrically charged objects; these can be extinguished using carbon dioxide, dry powder, or halon fire extinguishers (water is not suitable for use). How to select fire extinguishers: Different types of fire extinguishers should be used in various situations in order to achieve the best firefighting results and economic efficiency. 　--In areas with precision instruments and valuable equipment, residues of fire extinguishing agents can damage the equipment. Water and dry powder fire extinguishers should not be used; instead, gas fire extinguishers should be employed. 　---In places that house valuable books and archival materials, water should not be used to extinguish fires in order to avoid damage from water stains; instead, dry powder fire extinguishers or gas fire extinguishers should be used. 　　 　--In areas with electrical equipment, thermal expansion and contraction can cause the equipment to crack; water should not be used for extinguishing fires, and gas fire extinguishers or dry powder fire extinguishers with good insulating properties should be used instead. 　---In areas with high-temperature equipment, thermal expansion and contraction can cause the equipment to crack; water should not be used for extinguishing fires, and dry powder fire extinguishers or gas fire extinguishers should be used instead. 　—In areas where chemical hazardous materials are present, some fire extinguishing agents may react chemically with certain chemicals, potentially leading to an expansion of the fire; therefore, fire extinguishers that do not react chemically with these chemicals should be used. 　—In areas with flammable gases, gas leaks can lead to fires; therefore, water, which is effective at extinguishing flammable gas fires, should be used for firefighting.