UL Standard for Safety Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I@ II@ and III@ Division I@ Hazardous (Classified) Locations (Seventh Edition)
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. 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. 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. For the purposes of this standard@ normal atmospheric conditions are considered to be: a) An ambient temperature of 40??(104??; b) An oxygen concentration not greater than 21 percent by volume; and c) A pressure of one atmosphere. This standard does not cover apparatus based on high voltage electrostatic principles such as electrostatic paint spraying.