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DOE-HDBK-1092-98
meters, and similar devices would not ordinarily introduce a hazardous condition even though
used for flammable liquids or gases. Locations used for the storage of flammable liquids or of
liquefied or compressed gases in sealed containers would not normally be considered hazardous
unless also subject to other hazardous conditions.  Electrical conduits and their associated
enclosures separated from process fluids by a single seal or barrier are classed as a Division 2
location if the outside of the conduit and enclosures is a nonhazardous location.
Class II locations--Class II locations are those that are hazardous because of the presence of
combustible dust. Class II locations include the following:
a. Class II, Division 1--A Class II, Division 1 location is a location:
1. in which combustible dust is or may be in suspension in the air under normal operating
conditions, in quantities sufficient to produce explosive or ignitable mixtures; or
2. where mechanical failure or abnormal operation of machinery or equipment might cause
such explosive or ignitable mixtures to be produced, and might also provide a source of
ignition through simultaneous failure of electric equipment, operation of protection devices,
or from other causes, or
3. in which combustible dusts of an electrically conductive nature may be present.
NOTE: Combustible dusts which are electrically nonconductive include dusts produced in the
handling and processing of grain and grain products, pulverized sugar and cocoa, dried egg and
milk powders, pulverized spices, starch and pastes, potato and woodflour, oil meal from beans
and seed, dried hay, and other organic materials which may produce combustible dusts when
processed or handled. Dusts containing magnesium or aluminum are particularly hazardous and
the use of extreme caution is necessary to avoid ignition and explosion.
b. Class II, Division 2--A Class II, Division 2 location is a location in which:
1. combustible dust will not normally be in suspension in the air in quantities sufficient to
produce explosive or ignitable mixtures, and dust accumulations are normally insufficient
to interfere with the normal operation of electrical equipment or other apparatus; or
2. dust may be in suspension in the air as a result of infrequent malfunctioning of handling or
processing equipment, and dust accumulations resulting therefrom may be ignitable by
abnormal operation or failure of electrical equipment or other apparatus.
NOTE: This classification includes locations where dangerous concentrations of suspended dust
would not be likely but where dust accumulations might form on or in the vicinity of electric
equipment. These areas may contain equipment from which appreciable quantities of dust would
escape under abnormal operating conditions or be adjacent to a Class II Division 1 location, as
described above, into which an explosive or ignitable concentration of dust may be put into
suspension under abnormal operating conditions.
Class III locations--Class III locations are those that are hazardous because of the presence of easily
ignitable fibers or flyings but in which such fibers or flyings are not likely to be in suspension in the
air in quantities sufficient to produce ignitable mixtures. Class 111 locations include the following:
B-26


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