The Challenge
Combustible gases, vapors, and airborne dusts tend, by their very nature, to be explosive if present in the right concentrations along with sources of sparks or excess heat. Over the years, these hazards have led to some catastrophic losses of life and property. In response to this hazardous potential, regulatory bodies around the world, including Underwriters Laboratories, Inc., have worked to establish and refine a standard that will minimize the hazards associated with electrical equipment for use in these environments. UL 913, which was originally issued in 1971, is a U.S. national standard for “Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations.”
The purpose of this standard is to specify requirements for the construction and testing of electrical apparatus, or parts of such apparatus, having circuits that are not capable of causing ignition in Division 1 Hazardous (Classified) Locations as defined in Article 500 of the National Electrical Code, ANSI/ NFPA 70. Limiting sources of electrical spark energy and high surface temperatures and maintaining separation distances are key aspects of the UL 913 standard.
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