Circuit breaker cont'd - hdbk109220040233

DOE-HDBK-1092-2004

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.

ii. Class II, Division 2. A Class II, Division 2 location is a location in which:

a. 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

b. 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 III locations

include the following:

Class III, Division 1. A Class III, Division l location is a location in which easily ignitable fibers

or materials producing combustible flyings are handled, manufactured, or used.

NOTE: 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.

Easily ignitable fibers and flyings 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.

ii. Class III, Division 2. A Class III, Division 2 location is a location in which easily ignitable

fibers are stored or handled, except in process of manufacture.

Collector ring--A collector ring is an assembly of slip rings for transferring electrical energy from

a stationary to a rotating member.

Concealed--Rendered inaccessible by the structure or finish of the building. Wires in concealed

raceways are considered concealed, even though they may become accessible by withdrawing

them. [See "Accessible. (As applied to wiring methods.)"]

Conductor--

Bare--A conductor having no covering or electrical insulation whatsoever.

B-7