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Hazardous Location Definitions
Locations in which flammable gases or vapours are or may be present in the air in
quantities sufficient to produce explosive or ignitable mixtures.
Locations which are hazardous because of the presence of combustible dust.
Locations which are hazardous because of the presence of easily ignitable fibers
or flyings, but in which such fibers or flyings are not likely to be suspended in air in
quantities sufficient to produce ignitable mixtures.
Locations in which hazardous concentrations in the air exist continuously,
intermittently, or periodically under normal operating conditions.
Locations in which hazardous materials are handled, processed, or used, but
where such materials are normally within closed containers or closed systems from
which they can escape only in case of accidental rupture or breakdown.
Atmospheres containing acetylene.
Atmospheres containing hydrogen, or gases or vapours of equivalent hazard, such
as manufactured gas.
Atmospheres containing ethyl-ether vapours, ethylene, or cyclo-propane.
Atmospheres containing gasoline, hexane, naphtha, benzine, butane, propane,
alcohol, benzol, lacquer solvent vapours, or natural gas.
Atmospheres containing metal dust, including aluminum, magnesium and their
commercial alloys and other metals of similar hazardous characteristics.
Atmospheres containing carbon black, coal or coke dust.
Atmospheres containing flour, starch or grain dust.
Hazardous Location Definitions - International
The International Electrotechnical Commission (IEC) classifies hazardous
locations by Zone and Group. Zone is similar to the term "Division" in that it
defines the likelihood of hazard:
An area in which an explosive gas/air mixture is constantly present or present for
long periods of time.
An area in which an explosive gas/air mixture is likely to occur during normal
operation (Similar to Division 1).
An area in which an explosive/air mixture is not likely to occur but if so, only for
short periods of time (Similar to Division 2).
Pressure Switch
Reference
Class I
Class II
Class III
Division 1
Division 2
Group A
Group B
Group C
Group D
Group E
Group F
Group G
Zone 0
Zone 1
Zone 2