NFPA 496-2021 PDF Download

The NFPA 496-2021 standard aims to mitigate risks associated with electrical equipment fires, explosions, and other hazards in the presence of flammable atmospheres. It provides comprehensive criteria for the design and operation of purged and pressurized electrical equipment enclosures in Class I and Class II hazardous locations.

This standard applies to electrical equipment located in hazardous areas classified by Article 500 or Article 505 of the NFPA 70, National Electrical Code (NEC), 2020 edition. It also covers control rooms, buildings, and analyzer rooms containing sources of flammable vapors or gases in hazardous areas.

The revised NFPA 496 is updated to align with the latest knowledge and requirements of the NEC, 2020 edition. The standard includes significant changes in the annex sections, clarifying considerations for enclosure components, methods to prevent excessive protective gas pressure, prevention of ignition-capable particles discharge, and correlation with ANSI/ISA-12.04.04-2012, Pressurized Enclosures. Furthermore, it introduces requirements for alarms on pressurizing system bypasses, safety measures to prevent accidental opening, French translations of required markings, guidance on confirming the absence of trapped flammable gases, and revised indications of internal component protection and requirements based on internal volume.