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Subchapter 5. Electrical Safety Orders
Group 2. High-Voltage Electrical Safety Orders
Article 34. Hazardous (Classified) Locations (Formerly Article 83)
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§2925. General.

(a) Other Regulations.

(1) The requirements of this article shall be deemed to be additional to, or amendatory of, those prescribed in Group 2, inclusive, of these regulations.

(2) All provisions of Articles 59 and 60 of the Low-Voltage Electrical Safety Orders shall apply to high-voltage installations in hazardous (classifieds) locations.

(b) Scope. The provisions of this article shall apply to locations (except where otherwise provided for by statute) in which the apparatus and wiring are subject to the conditions indicated by the classifications in Section 2540.1 of the Low-Voltage Electrical Safety Orders. Where the apparatus and wiring are installed in rooms or sections of the building in which the particular flammable atmospheres do not prevail, such wiring and apparatus shall be permitted to be of the type approved for such locations.

(c) Enclosed areas supplied with positive pressure ventilation from a source free of flammable atmospheres shall be permitted to be classed as nonhazardous areas for the purpose of this Article if the following provisions are met:

(1) Division 1 Locations. Wiring and apparatus within this area shall be so arranged to prevent energizing the wiring and apparatus until ventilation has been established, and arranged to de-energize automatically the wiring and apparatus when the ventilation fails; provided, however, that where the process is such that a hazard would result from de-energizing wiring and apparatus, ventilation shall be permitted to be assured in this area through a separate source of supply for the ventilating equipment. Suitable devices shall be provided to transfer automatically from the normal supply to the emergency system in case of failure or damage to the normal supply. Audible and visual signal devices shall be provided, where feasible, to give warning of derangement of emergency supply system.

(2) Division 2 Locations. Wiring and apparatus within this area shall meet the requirements for Division 1 or as a minimum shall be arranged to energize an audible, as well as a visual, alarm on loss of pressurization. Removal of power in the latter case is not mandatory on loss of enclosure pressure except remedial action must be undertaken immediately. The enclosure shall be purged by ten air changes before electrical equipment is energized.

(d) Locations where open flames are ordinarily used will not be considered as being exposed to flammable atmospheres under this article.

(e) Special care shall be exercised in the layout of electrical installation to locate as much of the equipment as practicable in areas free of flammable atmospheres.

(Title 24, Part 3, Section 3-710-90.)

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Editorial correction including renumbering of former Article 83 to Article 34 filed 11-2-83 (Register 83, No. 45).

2. Amendment filed 12-10-87; operative 1-9-88 (Register 88, No. 1).

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