An explosive environment may occur. (Such as: combustible gas, dust environment, oil refinery, petrochemical plant, gas station, gas station, etc.), explosive gas atmosphere, gas, steam or mist-like combustible substance and air mixture, in the mixture After ignition, the combustion will spread throughout the environment of the unburnt mixture. (Such as: CH4, C2H2, C2H4, NH3, CO, C2H5OH and other explosion-proof electrical equipment)