This standard specifies the general requirements for construction, testing and marking of electrical apparatus and Ex components intended for use in Class I, Zone 0, 1, or 2 hazardous (classified) locations as defined by the National Electrical Code, ANSI/NFPA 70.

Unless modified by one of the parts of this standard, electrical apparatus complying with this standard is intended for use in hazardous areas in which explosive gas atmospheres, caused by mixtures of air and gases, vapours or mists, exist under normal atmospheric conditions of

• temperature –20 °C to +60 °C;

• pressure 80 kPa (0.8 bar) to 110 kPa (1.1 bar); and

• air with normal oxygen content, typically 21 % v/v.

The application of electrical apparatus in atmospheric conditions outside this range may need special consideration.

NOTE 1 The determination of the maximum surface temperature is based on an operational ambient temperature of –20 °C to +40 °C, if not otherwise specified by the manufacturer. See also 5.1.1.

NOTE 2 In designing apparatus for operation in explosive gas atmospheres under conditions other than the atmospheric conditions given above, this standard may be used as a guide. However, additional testing related specifically to the intended conditions of use is recommended. This is particularly important when the types of protection ‘flameproof enclosures "d"'  and ‘intrinsic safety "i"' are applied.

NOTE 3 Requirements given in this standard result from an ignition hazard assessment made on electrical equipment. The ignition sources taken into account are those found associated with this type of equipment, such as hot surfaces, mechanically generated sparks, thermite reactions, electrical arcing and static electric discharge in normal industrial environments. For other ignition sources like adiabatic compression, shock waves, exothermic chemical reaction, self ignition of dust, naked flames, hot gases/liquids the apparatus are subjected to a hazard analysis that identifies and lists all of the potential sources of ignition by the electrical apparatus and the measures to be applied to prevent them becoming effective.

This standard is supplemented or modified by the following standards concerning specific types of protection:

– Flameproof enclosures "d";

– Pressurized enclosures "p";

–  Powder filling "q";

– Oil immersion "o";

– Increased safety "e";

– Intrinsic safety "i";

– Type of protection "n";

– Encapsulation "m".

This standard is supplemented or modified by the following apparatus standards:

– ANSI/IEEE 515: Standard for Testing, Design, Installation, and Maintenance of Electrical Heat Tracing for Industrial Applications.

NOTE Components such as power connections, splices, end terminations, as well as cable entries, fittings, and seals are to be evaluated according to the type of protection employed.

This standard along with the additional standards mentioned above are not applicable to the construction of electromedical apparatus, shot-firing exploders, test devices for exploders and for shot-firing circuits.