Hazardous areas include potentially explosive vapors or dust. If these vapors or dust make their way into an electrical control panel, the normal arcing that occurs in electrical switching circuits could ignite these explosive vapors or dust and cause an explosion.
The official hazardous area classification system is changing, but the older classification system used three elements (Class, Division, Group) to describe hazardous areas.
Class refers to the general class or type of explosive substances in the area. Division refers to the degree of exposure to the explosive substances in the area. Group refers to the specific explosive substance in the area.
Class 1 means the area contains explosive vapors. Class 2 means the area contains explosive dust. Division 1 means the area is constantly exposed to the explosive substances. Division 2 means the area is only exposed to the explosive substances if an accident or leak occurs. Group describes the specific explosive vapor or dust.