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(a) Class II, Division 1. A Class II, Division 1 location is a location: (1) in which combustible dust
is 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 in hazardous quantities.
(FPN): 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 wood flour, oil meal from beans
and seed, dried hay, and other organic materials which may produce combustible dusts when
processed or handled. Electrically conductive dusts are dusts with a resistivity less than 105 ohm-
centimeter. Dusts containing magnesium or aluminum are particularly hazardous and the use of
extreme precaution will be necessary to avoid ignition and explosion.
(b) Class II, Division 2. A Class II, Division 2 location is a location where combustible dust is not
normally 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, but combustible dust may be in suspension in the air as a result
of infrequent malfunctioning of handling or processing equipment and where combustible dust
accumulations on, in, or in the vicinity of the electrical equipment may be sufficient to interfere
with the safe dissipation of heat from electrical equipment or may be ignitable by abnormal
operation or failure of electrical equipment.
(FPN No.1): The quantity of combustible dust that may be pre-sent and the adequacy of dust
removal systems are factors that merit consideration in determining the classification and may
result in an unclassified area.
(FPN No. 2): Where products such as seed are handled in a manner which produces low
quantities of dust, the amount of dust deposited may not warrant classification.
500-7. Class III Locations. Class III locations are those that are hazardous because of the
presence of easily ignitable fibers or filings, but in which such fibers or filings are not likely to be
in suspension in the air in quantities sufficient to produce ignitable mixtures. Class III locations
shall include those specified in (a) and (b) below.
(a) Class III, Division 1. A Class III, Division 1 location is a location in which easily ignitable
fibers or materials producing combustible filings are handled, manufactured, or used.
(FPN No. 1): Such locations usually include some parts of rayon, cotton, and other textile mills;
combustible fiber manufacturing and processing plants; cotton gins and cotton-seed mills; flax-
processing plants; clothing manufacturing plants; woodworking plants; and establishments and
industries involving similar hazardous processes or conditions.
(FPN No. 2): Easily ignitable fibers and filings include rayon, cotton (including cotton linters and
cotton waste), sisal or henequen, istle, jute, hemp, tow, cocoa fiber, oakum, baled waste kapok,
Spanish moss, excelsior, and other materials of similar nature.
(b) Class III, Division 2. A Class III, Division 2 location is a location in which easily ignitable
fibers are stored or handled.
E
T QUASAR Flare Monitors Operation Manual
Appendix B: Area Classification/Protection
2
Concepts • 60
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