FPN: Rules that are followed by a reference in brackets contain text that has been extracted from NFPA 497-
2004, Recommended Practice for the Classification of
Flammable Liquids, Gases, or Vapors and of Hazardous
(Classified) Locations for Electrical Installations in
Chemical Process Areas, and NFPA 499-2004,
Recommended Practice for the Classification of
Combustible Dusts and of Hazardous (Classified)
Locations for Electrical Installation in Chemical Process
Areas. Only editorial changes were made to the
extracted text to make it consistent with this Code.
500.1 Scope — Articles 500 Through 504. Articles 500 through 504 cover the requirements for electrical and electronic equipment and wiring for all voltages in Class I,Divisions 1 and 2; Class II, Divisions 1 and 2; and Class HI, Divisions 1 and 2 locations where fire or explosion hazards may exist due to flammable gases, flammable liquid-produced vapors, combustible liquid-produced va pors, combustible dusts, or ignitible fibers/flyings.
FPN No. 1: The unique hazards associated with explo- sives, pyrotechnics, and blasting agents are not addressed in this article.
FPN No. 2: For the requirements for electrical and electronic equipment and wiring for all voltages in Class I, Zone 0, Zone 1, and Zone 2 hazardous (classified) locations where fire or explosion hazards may exist due to flammable gases or vapors or flammable liquids, refer to Article 505.
FPN No. 3: For the requirements for electrical and electronic equipment and wiring for all voltages in Zone 20, Zone 21, and Zone 22 hazardous (classified) locations where fire or explosion hazards may exist due to combustible dusts or ignitible fibers/flyings, refer to Article 506.
500.2 Definitions. For purposes of Articles 500 through
504 and Articles 510 through 516, the following
definitions
apply.
Associated Nonincendive Field Wiring Apparatus. Ap- paratus in which the circuits are not necessarily nonincendive themselves but that affect the energy in nonincendive field wiring circuits and are relied upon to maintain nonincendive energy levels. Associated nonincendive field wiring apparatus may be either of the following:
(1) Electrical apparatus that has an alternative type of protection for use in the appropriate hazardous (classified) location
(2) Electrical apparatus not so protected that shall not be used in a hazardous (classified) location
FPN: Associated nonincendive field wiring apparatus has designated associated nonincendive field wiring apparatus connections for nonincendive field wiring apparatus and may also have connections for other electrical apparatus.
Combustible Gas Detection System. A protection technique utilizing stationary gas detectors in industrial establishments.
Control Drawing. A drawing or other document provided by the manufacturer of the intrinsically safe or associated apparatus, or of the nonincendive field wiring apparatus or associated nonincendive field wiring apparatus, that details the allowed interconnections between the intrinsically safe and associated apparatus or between the nonincendive field wiring apparatus or associated nonincendive field wiring apparatus.
Dust-Ignitionproof. Equipment enclosed in a manner that excludes dusts and does not permit arcs, sparks, or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure.
FPN: For further information on dust-ignitionproof enclosures,