§2540.11. Class I, Zone 0, 1, and 2 Locations.

(a) Scope. Employers may use the zone classification system as an alternative to the division classification system for electric 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.

(b) Location and General Requirements.

(1) Locations shall be classified depending on the properties of the flammable vapors, liquids, or gases that may be present and the likelihood that a flammable or combustible concentration or quantity is present. Where pyrophoric materials are the only materials used or handled, these locations need not be classified.

(2) Each room, section, or area shall be considered individually in determining its classification.

(c) Threading. All threaded conduit shall be threaded with an NPT [National (American) Standard Pipe Taper] standard conduit cutting die that provides 3/4- in. taper per foot. The conduit shall be made wrench tight to prevent sparking when fault current flows through the conduit system and to ensure the explosion-proof or flame-proof integrity of the conduit system where applicable.

Equipment provided with threaded entries for field wiring connection shall be installed in accordance with subsection (1) or (2) as follows:

(1) For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit, conduit fittings, or cable fittings shall be used.

(2) For equipment with metric threaded entries, such entries shall be identified as being metric, or listed adaptors to permit connection to conduit of NPT-threaded fittings shall be provided with the equipment. Adapters shall be used for connection to conduit or NPT-threaded fittings.

(d) Protection Techniques. One or more of the following protection techniques shall be used for electric and electronic equipment in hazardous (classified) locations classified under the zone classification system.

(1) Flameproof "d." This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

(2) Purged and pressurized. This protection technique is permitted for equipment in the Class I, Zone 1 or Zone 2 locations for which it is approved.

(3) Intrinsic safety. This protection technique is permitted for equipment in the Class I, Zone 0 or Zone 1 locations for which it is approved.

(4) Type of protection "n." This protection technique is permitted for equipment in the Class I, Zone 2 locations for which it is approved. Type of protection "n" is further subdivided into nA, nC, and nR.

(5) Oil Immersion "o." This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

(6) Increased safety "e." This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

(7) Encapsulation "m." This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

(8) Powder Filling "q." This protection technique is permitted for equipment in the Class I, Zone 1 locations for which it is approved.

(e) Special Precaution. This Article (Article 59) requires equipment construction and installation that will ensure safe performance under conditions of proper use and maintenance.

(1) Classification of areas and selection of equipment and wiring methods shall be under the supervision of a qualified registered professional engineer.

(2) In instances of areas within the same facility classified separately, Class I, Zone 2 locations may abut, but not overlap, Class I, Division 2 locations. Class I, Zone 0 or Zone 1 locations shall not abut Class I, Division 1 or Division 2 locations.

(3) A Class I, Division 1 or Division 2 location may be reclassified as a Class I, Zone 0, Zone 1, or Zone 2 location only if all of the space that is classified because of a single flammable gas or vapor source is reclassified.

NOTE to subsection (e): Low ambient conditions require special consideration. Electric equipment depending on the protection techniques described by subsection (d)(1) of this section may not be suitable for use at temperatures lower than -20 degrees C (-4 degrees F) unless they are approved for use at lower temperatures. However, at low ambient temperatures, flammable concentrations of vapors may not exist in a location classified Class I, Zone 0, 1, or 2 at normal ambient temperature.

(f) Listing and Marking.

(1) Equipment that is listed for a Zone 0 location may be installed in a Zone 1 or Zone 2 location of the same gas or vapor. Equipment that is listed for a Zone 1 location may be installed in a Zone 2 location of the same gas or vapor.

(2) Equipment shall be marked in accordance with subsections (f)(2)(A) or (f)(2)(B) as follows:

(A) Division equipment. Equipment approved for Class I, Division 1 or Class 1, Division 2 shall, in addition to being marked in accordance with Section 2540.3(b)(2)(B), be marked with the following:

1. Class I, Zone 1 or Class I, Zone 2 (as applicable);

2. Applicable gas classification groups; and

3. Temperature classification; or

(B) Zone equipment. Equipment meeting one or more of the protection techniques described in subsection (d) of this section shall be marked with the following in the order shown:

1. Class, except for intrinsically safe apparatus;

2. Zone, except for intrinsically safe apparatus;

3. Symbol "AEx;"

4. Protection techniques;

5. Applicable gas classification groups; and

6. Temperature classification, except for intrinsically safe apparatus.

NOTE to subsection (f)(2)(B): An example of such a required marking is "Class I, Zone 0, AEx ia IIC T6." See Figure S-1 for an explanation of this marking.

Exception: to (f)(2): Equipment that the employer demonstrates will provide protection from the hazards arising from the flammability of the gas or vapor and the zone of location involved and will be recognized as providing such protection by employees need not be marked.

NOTE for EXCEPTION: The National Electrical Code, NFPA 70, contains guidelines for determining the type and design of equipment and installations that will meet this provision.

Figure S-1 -Example Marking for Class I, Zone 0, AEx ia IIC T6

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

HISTORY

1. New section filed 5-5-2008; operative 5-5-2008. Submitted to OAL for printing only pursuant to Labor Code 142.3(a)(3) (Register 2008, No. 19).

Go Back to Article 59 Table of Contents