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. Only editorial changes were
made to the extracted text to make it consistent
with this Code.
505.1 Scope. This article covers the requirements for the zone classification system as an alternative to the division classification system covered in Article 500 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, vapors, or liquids.
FPN: For the requirements for electrical and electronic equipment and wiring for all voltages in Class I, Division
1 or Division 2; Class II, Division 1 or Division 2; and Class
III, Division 1 or Division 2 hazardous (classified) loca- tions where fire or explosion hazards may exist due to
flammable gases or vapors, flammable liquids, or combustible dusts or fibers, refer to Articles 500 through 504.
505.2 Definitions. For purposes of this article, the following definitions apply.
Combustible Gas Detection System. A protection tech- nique utilizing stationary gas detectors in industrial establishments.
Electrical and Electronic Equipment Materials, fittings, devices, appliances, and the like that are part of, or in connection with, an electrical installation.
FPN: Portable or transportable equipment having self- contained power supplies, such as battery-operated equip ment, could potentially become an ignition source in hazardous (classified) locations.
Encapsulation "m." Type of protection where electrical parts that could ignite an explosive atmosphere by either sparking or heating are enclosed in a compound in such a way that this explosive atmosphere cannot be ignited.
FPN No. 1: See ANSl/ISA-60079-18 (12.23.01>2005, Electrical Apparatus for Use in Class I, Zone 1 Hazardous (Classified) Locations, Type of Protection — Encapsulation "m"; IEC 60079-18-1992, Electrical apparatus for explosive gas atmospheres — Part 18: Encapsulation "m"; and ANSI/UL 60079-18, Electrical
Apparatus for Explosive Gas Atmospheres — Part 18: Encapsulation "m".
FPN No. 2: Encapsulation is designated type of protection "ma" for use in Zone 0 locations. Encapsulation is designated type of protection "m" or "mb" for use in Zone 1 locations.
Flameproof "d." Type of protection where the enclosure will withstand an internal explosion of a flammable mixture that has penetrated into the interior, without suffering damage and without causing ignition, through any joints or structural openings in the enclosure, of an external explosive gas atmosphere consisting of one or more of the gases or vapors for which it is designed.
FPN: See ANSI/ISA-60079-1 (12.22.01 )-2005, Electrical Apparatus for Use in Class I, Zone 1 and 2 Hazardous (Classified) Locations, Type of Protection — Flameproof "d"; and ANSI/UL 60079-1, Electrical Apparatus for Explosive Gas Atmospheres — Part 1: Flameproof Enclosures "d"