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6/08 ST 3000 Release 300 and SFC Model STS103 User’s Manual 253
Appendix D – Hazardous Locations Reference
Reference
Information
Information is provided to clarify the hazardous location installation
requirements in North America and internationally. An explanation of
the applicable enclosure classification systems is also provided.
D.1 North American Classification of Hazardous Locations
Electrical Codes
Installation of electrical apparatus within hazardous (classified)
locations of the United States is conducted under the provisions of the
National Electrical Code (NEC), ANSI/NFPA 70, Article 500; and
within Canada, under the provisions of the Canadian Electrical Code
(CEC) C22.1, Part 1, Section 18.
Classes
Hazardous (classified) locations, in both the United States and Canada,
are categorized into one of these three classes.
Class Description of Hazardous Location
I
Presence of flammable gases or vapors may be present in
quantities sufficient to produce explosive or ignitable mixtures.
II
Presence of combustible dusts, powders or grains.
III
Presence of easily ignitable fibers or flyings.
Divisions
The classes listed above are further categorized based upon the level of
risk present.
Division Description of Risk
1
Locations in which hazardous concentrations of flammable gases
or vapors, or combustible dust in suspension are continuously,
intermittently or periodically present under normal operating
conditions.
2
Locations in which flammable gases or vapors are present, but
normally confined within closed containers or systems from which
they can escape only under abnormal or fault conditions.
Combustible dusts are not normally in suspension nor likely to be
thrown into suspension.
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