UL 913

1.1 * These requirements apply to apparatus or parts of apparatus for installation and use in Class I, II, or III, Division 1 hazardous (classified) locations in accordance with the requirements of the National Electrical Code, NFPA 70, the Rules of the Canadian Electrical Code, Part I, and gassy underground mines.

1.2 * These requirements also cover associated apparatus located outside of the Class I, II or III, Division 1 location whose design and construction may influence the intrinsic safety of an electrical circuit within the Class I, II or III, Division 1 location.

1.3 * These requirements also apply to apparatus or parts of apparatus for installation and use in Class I, Zone 0 or 1, Groups I, IIC, IIB and IIA hazardous (classified) locations as defined in Article 505 of the National Electrical Code, NFPA 70.

1.4 * These requirements also cover associated apparatus located outside of the Class I, Zone 0 or 1, Groups I, IIC, IIB and IIA location whose design and construction may influence the intrinsic safety of an electrical circuit within the Class I, Zone 0 or 1, Group I, IIA, IIB, or IIC location.

1.5 These requirements are based on consideration of ignition in locations classified as a hazardous location by the presence of flammable or combustible material under normal atmospheric conditions.

1.6 * For the purposes of this standard, normal atmospheric conditions are considered to be:

1. An ambient temperature of 40?C (104?F);
2. An oxygen concentration not greater than 21 percent by volume; and
3. A pressure of one atmosphere.

1.7 Equipment specified for use in other than normal atmospheric conditions may be subject to additional investigation.

1.8 This standard does not cover mechanisms of ignition from external sources such as static electricity or lightning, which are not related to the electrical characteristics of the apparatus.

1.9 This standard does not cover apparatus based on high voltage electrostatic principles such as electrostatic paint spraying.