Sulfur hexafluoride gas should be tested according to national standards.The test items include air(N2,O2),carbon tetrafluoride(CF4),sulfur hexafluoride(SF6)purity test,SF6 moisture test(H2O),acidity(calculated by HF),hydrolyzable fluoride(calculated by HF),mineral oil and toxic biological test.The test results shall comply with the provisions of GB/T12022.

　　(1)when the humidity of sulfur hexafluoride gas is large,if there is an arc in the equipment,the arc decomposition of the gas will produce many toxic substances under the participation of water,such as SOF2,HF,etc.,thus corroding the internal structure materials of the circuit breaker and threatening the personal safety of maintenance personnel.Also,when the humidity is high.With the change of temperature,condensed water is produced on the surface of the insulation,causing flashover along the surface.The insulation strength decreases,threatening the safe operation of equipment.

　　(2)the air,carbon tetrafluoride,impurities such as mineral oil can reduce insulation and arc extinguishing performance of electrical equipment in a large current,high voltage,high temperature under the influence of external factors,such as the presence of oxygen and moisture will produce toxic or toxic oxygen low fluoride,these impurities does great harm to human body,and the metal components of equipment corrosion and insulation.

　　(3)Acidity represents or symbolizes the toxicity of sulfur hexafluoride gas to a certain extent,especially when acidic components and water exist at the same time,condensation may occur,which will seriously endanger the safe operation of electrical equipment.

　　(4)Low fluoride containing sulfur in high purity sulfur hexafluoride impurities.Some of them are easily hydrolyzed to form acidic or toxic substances,damaging human health and equipment operation safety.