NFPA 496

Abstract

Scope: This standard applies to purging and pressurizing for the following: (1) Electrical equipment located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70 (2) Electrical equipment containing sources of flammable vapors or gases and located in either classified or unclassified areas (3) Control rooms or buildings located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70 (4) Analyzer rooms containing sources of flammable vapors or gases and located in areas classified as hazardous by Article 500 or Article 505 of NFPA 70 This standard does not apply to electrical equipment located in: (1) Areas classified as Class I, Zone 0 (2) Areas classified as Class III (3) Areas where flammable liquids may be splashed or spilled on the electrical equipment Purpose. This standard provides information on the methods for purging and pressurizing enclosures to prevent ignition of a flammable atmosphere. Such an atmosphere may be introduced into the enclosure by a surrounding external atmosphere or by an internal source. By these means, electrical equipment that is not otherwise acceptable for a flammable atmosphere may be utilized in accordance with Article 500 or Article 505 of NFPA 70