Hazardous locations light is looked as explosion proof lighting used in hazardous locations for NEC500 standard. Depends on the flammable ingredient group, class 1 means hazardous gas and vapor, class 2 means hazardous dust, class 3 means hazardous fiber. Classified by the frequency the flammable ingredient present in locations, class 1 division 1 means hazardous gas and vapor present intermittently (more than 10 hours every year), class 2 division 1 means hazardous dust present intermittently (more than 10 hours every year), class 1 division 2 means hazardous gas and vapor present abnormally (less than 10 hours every year), class 2 division 2 means hazardous dust present abnormally (less than 10 hours every year). So the hazardous locations light has five types, class 1 division 1 light, class 1 division 2 light, class 2 division 1 light, class 2 division 2 light and class 3 light.