Areas where fire or explosion hazards may exist.  HazLoc is categorized by Classes, Divisions, and Groups depending on the type of substances involved and the likeness of those substances to be present. Class I, Division 2, Groups A-D Hazardous Locations include places where flammable gases or vapors such as acetylene, hydrogen, butadiene, ethylene oxide, propylene oxide, acrolein, carbon monoxide, ether, hydrogen sulfide, morphline, cyclopropane, ethyl, isoprene, acetaldehyde, ethylene, gasoline, acetone, ammonia, benzene, butane, ethanol, hexane, methanol, methane, vinyl chloride, natural gas, naphtha, propane, gasoline, acetylene, hydrogen, ethylene, propane, acetone, methane are processed but are not normally present in concentrations high enough to be ignitable (but may accidentally exist).