Explosion proof electrical equipment is divided into two categories: Category I refers to electrical equipment used underground in coal mines; II refers to electrical equipment used in places other than mines, classified according to the maximum test safety gap (MESG) or minimum ignition current (MICR). Class II electrical equipment is further divided into three categories: IIA, IIB, and IIC.

　　The above four categories are mainly based on the small spark energy that may ignite under different working conditions. China, Europe, and most countries and regions in the world classify explosive gases into these four hazard levels. The specific differences are shown in the table below. Secondly, according to the difference in ignition temperature of explosive gas mixtures, the groups are further divided into six types: T1, T2, T3, T4, T5, T6, and the ignition temperature is represented by t (℃).