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Feb 10, 2019

Bill BurrBy William (Bill) Burr

The Code is a comprehensive document. Sometimes it can seem quite daunting to quickly find the information you need. This series of articles provides a guide to help users find their way through this critical document. This is not intended to replace the notes in Appendix B or the explanations of individual requirements contained in the CEC Handbook** but will hopefully provide some help in navigating, while reading the code. The 24th Edition of the CE-C, Part I, (C22.1-18)* is now available from CSA Group.

In this article: Annex J18, which is permitted, optionally, for use in additions, modifications, renovations or operation and maintenance of existing facilities employing the division system of classification. The rules of Annex J18 are normative (mandatory) where used and amend or supplement other requirements of the Code. Additional informative (non-mandatory) information is contained in Annex JB. Due to the size of this annex, it will be discussed in multiple parts. This is Part A.

Annex J18 is divided into four parts — General, Class I, Class II and Class III locations:

    • Class I location — where flammable gases or vapours may be present in explosive quantities
    • Class II location — where combustible or electrically conductive combustible dusts are present
    •  Class III location — where easily ignitable fibres or flyings are present in sufficient quantities to produce ignitable mixtures

Rule J18-002 provides special terminology definitions for terms used in this section that are supplementary to the definitions in Section 0.

Rule J18-004 Divides Class I locations into


    • Division 1 locations where explosive gas atmospheres are present continuously, intermittently or periodically during normal operation
    • Division 2 locations where explosive gas atmospheres occur only abnormally and for a short time or locations adjacent to a Division 1 where explosive gases could be communicated

Rule J18-006 Divides Class II locations into

    • Division 1 where, under normal operating conditions or abnormal operation or failure of equipment, combustible dust may be in suspension continuously, intermittently or periodically in sufficient quantities to produce explosive or ignitable mixtures, or conduct electricity, and

    • Division 2 where, under infrequent malfunctioning of handling or processing equipment, combustible dust may


        ◦ be present in quantities sufficient to produce explosive or ignitable mixtures but only for short periods of time, or

        ◦ develop combustible dust accumulations on equipment sufficient to interfere with safe dissipation of heat or become ignitable by operational failure of equipment

Rule J18-008 divides Class III locations into

    • Division 1 locations where readily ignitable fibres or materials producing combustible flyings are handled, manufactured, or used
    • Division 2 locations where readily ignitable fibres other than those in process of manufacture are stored or handled

Rule J18-010 provides that unauthorized repairs or alterations shall not be made on live equipment and that equipment shall be maintained in its original safe condition.


The General Part of Annex J18 applies to all installations and equipment installed under this annex.


Rules J18-050 and J18-052 require that electrical equipment installed in Class I, II, or III hazardous locations shall have markings suitable for the class and division in which the equipment is installed and be marked for the class of location and the specific material that will be present:

    • for Class I, the specific gas with the atmospheric Group designation —

        ◦ Group A - acetylene

        ◦ Group B - butadiene, ethylene oxide, hydrogen, manufactured gas), or propylene oxide

        ◦ Group C - acetaldehyde, cyclopropane, diethyl ether, ethylene, hydrogen sulphide, or unsymmetrical dimethyl hydrazine (UDMH), or other gases or vapours of equivalent hazard, or


        ◦ Group D - acetone, acrylonitrile, alcohol, ammonia, benzine, benzoyl, butane, ethylene dichloride, gasoline, hexane, isoprene, lacquer solvent vapours, naphtha, natural gas, propane, propylene, styrene, vinyl acetate, vinyl chloride, xylene, or other gases or vapours of equivalent hazard

    • For Class II, the specific dust with the atmospheric group designations —

        ◦ Group E — combustible metal dust, aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics

        ◦ Group F — carbon black, coal, or coke dust, or

        ◦ Group G — flour, starch, or grain dust, and other dusts of similarly hazardous characteristics

Rule J18-054 specifies that the maximum surface temperature rating marked on equipment shall for

    • Class I locations — not exceed the minimum ignition temperature for the location

    • Class II locations — not exceed the lower of the dust cloud or dust layer ignition temperature for the location, or for organic dusts, the lower of 165 degrees centigrade or ignition temperature for the location

    • Class III locations — not exceed 165 °C for equipment that is not subject to overloading and 120 °C for equipment (such as motors or power transformers) that may be overloaded

    • equipment installed in accordance with Rule J18-150 2) or 3) - have surface temperatures at any point on the equipment that may be exposed to an explosive gas atmosphere not to exceed the minimum ignition temperature determined for the hazardous location in which the equipment is installed


    • equipment with no maximum surface temperature rating marked on Class I or Class II equipment - marked for the Class and Group, the maximum surface temperature rating shall be deemed to be 100°C

Rule J18-056 states that each room, section or area must be considered a separate location for determining the classification of the hazard.

Rule J18-058 requires that

    • walls, partitions, floors, or ceilings used to form hazard-free rooms or sections, of equipment rooms, be of substantial construction; built of or lined with non-combustible material, and such that the rooms or sections will remain free from hazards

    • locations within a building that communicate with a Class I, Division 2 location, be separated by close-fitting, self-closing, approved fire doors

    • for communication from a Class I, Division 1 location, the provisions of Rule J18-004 b) ii) apply

Rule J18-060 requires that where

    • exposed overhead conductors supply metal-covered mineral-insulated cable, surge arresters, to limit voltage to 5kV, be installed

    • single-conductor metal-covered cable used in hazardous locations, be installed to prevent sparking between cable sheaths or between cable sheaths and metal bonded to ground; clipped or strapped together in a manner that will ensure good electrical contact between metal coverings, at intervals of not more than 1.8 m, and the metal coverings be bonded to ground; or have the metal coverings continuously covered with insulating material and bonded to ground at the point of termination in the hazardous location only

Rule J18-062 permits the provisions of rules J18-100 to J18-160 to be suspended for Class I location type electrical equipment and wiring located in pressurized equipment rooms or enclosures constructed and arranged so that a protective gas pressure is effectively maintained.


Rule J18-064 requires that intrinsically safe and non-incendive electrical equipment and wiring installed in a hazardous location

    • be provided with, and installed in accordance with, the descriptive system document as described in Appendix F

    • be separated by not less than 50 mm, the metal armour or sheath of cable assemblies, a grounded metal barrier not less than 1.34 mm (No. 16 MSG) thick, or a non-metallic insulating material not less than 1.5 mm in thickness

where insulated conductors of intrinsically safe or non-incendive field wiring are installed in a raceway, compartment, enclosure, outlet, junction box, or any similar fitting, with insulated conductors of any other circuit

    • insulated conductors of different intrinsically safe or non-incendive field wiring circuits may be installed in the same raceway, compartment, outlet, junction box, or multi-conductor cable, provided that the insulated conductors of each circuit are within grounded electrically conductive shields, braids, or sheaths; or the insulated conductors of each circuit have insulation with a minimum thickness of 0.25 mm

    • raceways or cable systems for intrinsically safe and non-incendive wiring and equipment in explosive atmospheres be installed to minimize migration of flammable fluids to other locations


    • apparatus forming part of an intrinsically safe or non-incendive system be identified as such

    • intrinsically safe and non-incendive field wiring circuits be identified at terminal and junction locations


    • wiring methods for intrinsically safe and or non-incendive field wiring circuits be identified with permanently affixed labels, or colour coded light blue where no other cables or insulated conductors coloured light blue are used

Rule J18-066 specifies that electrical equipment suitable for non-hazardous locations may be installed in a Class I, Division 2 hazardous location, and electrical equipment suitable for Class I, Division 2 hazardous locations may be installed in a Class I, Division 1 hazardous location, provided that

    • no specific equipment suitable for the purpose is available


    • the equipment, during its normal operation, does not produce arcs, sparks, or hot surfaces capable of igniting an explosive gas atmosphere

    • the location is continuously monitored by a combustible gas detection system, as described in Appendix H, that

        ◦ activates an alarm when the gas concentration reaches 20% of the lower flammable limit;


        ◦ activates ventilating equipment or other means designed to prevent the concentration of gas from reaching the lower flammable limit when the gas

concentration reaches 20% of the lower flammable limit, where such ventilating equipment or other means is provided;


        ◦ automatically de-energizes the electrical equipment being protected when the gas concentration reaches 40% of the lower flammable limit, where the ventilating equipment is provided;


        ◦ automatically de-energizes the electrical equipment being protected when the gas concentration reaches 20% of the lower flammable limit, where the ventilating equipment cannot be provided; and

        ◦ automatically de-energizes the electrical equipment being protected upon failure of the gas detection instrument.

Rule J18-068 requires electrical equipment with a primary flammable fluid seal in contact with flammable fluids


    • be constructed and installed to prevent migration of flammable fluid through the wiring system, and at pressures lower than the marked maximum working pressure (MWP)

    • Where the above is met through the installation of secondary seals, the possibility of primary seal failure be obviously indicated, or marking means indicating that the enclosure may contain flammable fluid under pressure


Rule J18-070 reiterates that exposed non-current-carrying metal parts of electrical equipment, including the frames or metal exteriors of motors, fixed or portable luminaires or other utilization equipment, luminaires, cabinets, cases, and conduit, shall be bonded to ground in accordance with Section 10.


Rule J18-072 prohibits any uninsulated exposed parts of an electrical installation or of electrical equipment such as conductors, buses, terminals, or components in a hazardous location unless

    • they operate at less than 30 V (15 V in wet locations) and are additionally protected by a type of protection suitable for the location, or


    • as provided for in Rule J18-324 for electric cranes, hoists, and similar equipment in a Class III location


In the next instalment, we will be discussing Part B, Class I locations of Annex J18, of Appendix J.


* The source for this series of articles is the Canadian Electrical Code, Part I, (C22.1-18) published by CSA.
** Note the CEC Handbook is also published by CSA.

William (Bill) Burr is the former Chair of the Canadian Advisory Council on Electrical Safety (CACES), former Director of Electrical and Elevator Safety for the Province of BC, and former Director of Electrical and Gas Standards Development and former Director of Conformity Assessment at CSA Group. Bill can be reached at Burr and Associates Consulting billburr@gmail.com.