If the purity of sulfur hexafluoride gas is low,its insulation strength will be greatly decreased,and it is easy to be broken down by high voltage when used in electrical insulation,causing accidents.So what causes the impure gas purity?

　　(1)As we all know,at present,sulfur hexafluoride gas is mainly produced by the direct reaction of elemental sulfur and excess gaseous fluorine in the chemical industry.There are a variety of impurities in the synthetic crude products.The composition and content of impurities vary greatly due to the purity of raw materials,the material of production equipment and technological conditions,etc.The total content of impurities can reach 5%.

　　In addition,a small amount of air,water,mineral oil and other impurities may be mixed in the filling process of the gas,and these impurities have or will produce certain toxic substances.

　　(2)the SF6 gas in electrical equipment produces some toxic products when the high temperature arc occurs.

　　(3)the decomposition of sulfur hexafluoride gas in electrical equipment reacts with the water in it to produce some toxic products.

　　(4)Electrical equipment in the SF6 gas and decomposition and electrode(Cu-W alloy)and metal materials(AL,Cu)reaction to generate some toxic products.

　　(5)the SF6 gas and decomposition of electrical equipment react with insulation materials and generate some toxic products.For example,SiF4,Si(CH3)2F2 and other products can be generated by chemical reaction with epoxy phenolic glass filament cloth plate(rod,tube)containing silicon,or epoxy resin castable parts,moulded parts with quartz sand and glass as fillers,porcelain bottles,silicone rubber,silicone grease,etc.

　　The above products of high purity sulfur hexafluoride decomposition at high temperature will lead to the problem of impure gas purity.In addition,the gas in the equipment should be frequently detected and replaced to avoid damage to the equipment.