This standard applies to equipment made suitable for use in hazardous (classified) locations by pressurizing the use of a pressurizing system. 

This standard applies both to equipment with and without an internal release of a flammable gas or vapor. 

This standard does not apply to occupied portions of buildings such as ventilated or pressurized control rooms.

Purpose

This standard provides guidance to those who employ pressurization for electrical equipment in hazardous (classified) locations, and should be used in conjunction with ANSI/NFPA 496, Purged and Pressurized Enclosures for Electrical Equipment . 

This standard provides performance and test recommendations so that the enclosure and components mounted internally or protruding through the enclosure are unlikely to cause ignition of a surrounding flammable atmosphere. 

This standard provides performance and test recommendations so that users are unlikely to be injured by rupture of the enclosure due to failure of the pressure -regulating devices in the PROTECTIVE GAS SUPPLY.