The substance that can effectively destroy the combustion conditions in the combustion zone to inhibit or stop the combustion is called a fire extinguishing agent.

　　Various fire extinguishing agents have the following functions respectively.

　　(1)Cool down and lower the combustion temperature.

　　(2)Suffocate and prevent air from entering the combustion zone.

　　(3)Isolate and prevent combustible flow to the combustion zone.

　　(4)Inhibit the chain reaction.

　　(5)Dilute the concentration of combustible gas and combustible liquid and reduce the oxygen content in the air.

　　Classification of fire extinguishing agents

　　According to the usual existing state,fire extinguishing agents can be divided into three categories,namely,liquid fire extinguishing agents,gas fire extinguishing agents and solid fire extinguishing agents.

　　Liquid fire extinguishing agent

　　Most of these fire extinguishing agents are mixtures of aqueous solutions of multiple compounds.Liquid fire extinguishing agents include three types:water and additives,foam fire extinguishing agent,and 7150 fire extinguishing agent.

　　Gas fire extinguishing agent

　　This type of fire extinguishing agent exists in gaseous or liquid form in storage,and extinguishes fire in gaseous form.It can be used for A,B,C type fire fighting and fire fighting with point equipment.There are two main types:non-combustible gas fire extinguishing agent and halogenated alkane fire extinguishing agent.

　　Solid fire extinguishing agent

　　This type of fire extinguishing agent is solid at room temperature and is a mixture of solid powders.Including dry powder fire extinguishing agent,powder fire extinguishing agent and aerosol fire extinguishing agent three types.

　　Water is a very common fire extinguishing agent.It is easy to access and has abundant sources,so it is widely used on fire scenes.General building fires,solid combustible materials such as wood,coal,grain,cotton and linen,and liquid combustible materials such as crude oil and heavy oil can be extinguished with water.