1. Class: Defines the type of hazardous environment
Class I: Environments where flammable gases or vapors are present. (e.g., refineries, chemical plants, gas stations) Class II: Environments where combustible dust is present. (e.g., flour mills, coal dust storage, grain processing plants) Class III: Environments where flammable fibers or fluff are present. (e.g., textile mills, wood processing plants)
2. Division: Defines the probability or frequency of hazardous substances occurring
Division 1: Hazardous substances may be present under normal operating conditions. Division 2: Hazardous substances may only be present under abnormal conditions (e.g., container rupture, equipment failure) or are normally confined within sealed containers.
3. Group: Further defines specific types of combustible substances
Group A: Acetylene. Group B: Hydrogen, etc. Group C: Ethylene, carbon monoxide, etc. Group D: Propane, methane (natural gas), gasoline, etc. Group F: Carbonaceous dust (e.g., coal dust, coke dust). Group G: Combustible dust (e.g., flour, grain, starch, plastic dust).
