UL 913

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Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations
UL 913
1 Scope
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.

1.2 These requirements also apply to apparatus or parts of apparatus for installation and use in Zone 20, Groups IIIA, IIIB, and IIIC hazardous (classified) locations in accordance with the requirements of the National Electrical Code, NFPA 70.

1.3 * These requirements also cover associated apparatus located outside of the hazardous (classified) location whose design and construction may influence the intrinsic safety of an electrical circuit within the hazardous (classified) location.

1.4 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.

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

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

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