Environment where an explosive atmosphere will probably not be present under normal operating this will, Conditions and be for, If any short period of time, That is, An explosive atmosphere may be present accidentally. The environments are classified as zone 2, Groups iia, Iib and iic. The most common gases included in this classification are acetone, Ammonia, Benzene, Butane, Butanol, Buthylic alcohol, Ethane, Ethanol, Acetate of ethyl, Gasoline, Heptanes, Hexanes, Natural gas, Methanol, Oil naphtha, Propane, Propanol, Toluene, Esthyrene, Solvents in general, Acetaldehyde, Cyclopropane, Diethylic ether, Ethane, Monoxide of carbon, Acetylene, Butadiene, Oxide of ethane, Hydrogen, Oxide of propylene and gases containing over 30% of hydrogen.