According to definitions in the Canadian Electrical Code, U.S. National Electrical Code, IEC 60079-10 and CENELEC EN 60079-10, hazardous locations are defined when fire or explosion may result from the presence of:
Class I: Flammable gases, vapors or liquids
Class II: Combustible dusts
Class III: Ignitable fibers or flyings
Division 1 – A location where a classified hazard exists or is likely to exist under normal conditions
Division 2 – A location where a classified hazard does not normally exist but is possible to appear under abnormal conditions
North American transition to the zone system
The U.S. and Canada have recently revised installation codes to recognize an international 3-Zone area classification system for equipment used in hazardous locations.
Zone 0 – An area in which an explosive gas atmosphere is continuously present for a long period of time
Zone 1 – An area in which an explosive atmosphere is likely to occur in normal operation
Zone 2 – An area in which an explosive gas atmosphere does not normally exist.