Explosion-proof lighting is classified into three main classes (I, II, and III), each further divided into Divisions (1 or 2) based on the presence and frequency of hazardous materials in the environment. Class I deals with flammable gases and vapors, Class II with combustible dusts, and Class III with ignitable fibers and flyings. Divisions 1 and 2 indicate whether the hazardous materials are present under normal or abnormal operating conditions, respectively

Class I:

This class covers locations where flammable gases, vapors, or liquids are present in the atmosphere.

• Division 1: Hazardous concentrations of flammable substances are likely to exist under normal operating conditions.

• Division 2: Hazardous concentrations of flammable substances are unlikely to exist under normal operating conditions, but may exist under abnormal conditions (like equipment failure)

• Class II:

This class covers locations where combustible dust is present in the atmosphere.

• Division 1: Hazardous concentrations of combustible dust are likely to exist under normal operating conditions.

• Division 2: Hazardous concentrations of combustible dust are unlikely to exist under normal operating conditions, but may exist under abnormal conditions.

• Class III:

This class covers locations where ignitable fibers or flyings are present in the atmosphere.

• Division 1: Hazardous concentrations of ignitable fibers or flyings are likely to exist under normal operating conditions.

• Division 2: Hazardous concentrations of ignitable fibers or flyings are unlikely to exist under normal operating conditions, but may exist under abnormal conditions. 

• Groups:

• Within Class I and Class II, there are further subdivisions called Groups (e.g., Groups A, B, C, and D for Class I) that categorize the specific types of hazardous materials based on their ignitability