Class I: underground electrical equipment in coal mines;

Class II: Electrical equipment for explosive gas environments other than coal mines and underground mines.

ⅱclass can be divided into ⅡA, ⅡB, ⅡC class, marking ⅡB equipment can be applied to the conditions of use of ⅡA equipment; ⅡC can be used under the conditions of ⅡA and ⅡB.

Class III: Electrical equipment for explosive dust environments other than coal mines.

ⅲClass A: Combustible floc; ⅲClass B: non-conductive dust; Ⅲ Class C: conductive dust.