This recommended practice applies to equipment made suitable for use in hazardous (classified) locations by the use of a pressurizing system. This recommended practice applies both to equipment with and without an internal release of a flammable gas or vapor. This recommended practice does not apply to occupied portions of buildings such as ventilated or pressurized control rooms. Purpose This recommended practice provides guidance to those who design and install pressurized systems for hazardous (classified) locations@ and should be used in conjunction with ANSI/NFPA 496@ Purged and Pressurized Enclosures for Electrical Equipment. This recommended practice 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 recommended practice 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.