2017 NFPA 496 Standard - Current Edition
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  • Description

    Install electrical equipment in Class I and Class II hazardous (classified) locations to prevent ignition of a flammable atmosphere. The 2017 edition of NFPA 496 helps you protect people, equipment, and facilities from potentially deadly hazards.

    Work with the specialized knowledge you need to head off electrical equipment fires and explosions. Consistent with the 2017 edition of NFPA 70®: National Electrical Code® (NEC®), the 2017 edition of NFPA 496: Standard for Purged and Pressurized Enclosures for Electrical Equipment contains requirements for the design and operation of purged and pressurized electrical equipment enclosures.

    This protection technique is used in Class I and Class II hazardous (classified) locations to reduce or prevent the presence of flammable materials within electrical equipment enclosures as specified by the NEC.

    Electrical designers, installers, and AHJs reference NFPA 496 for vital requirements concerning:

    • General Requirements for Pressurized Enclosures
    • Pressurized Enclosures for Class I
    • Pressurized Enclosures for Class II
    • Pressurized Control Rooms
    • Pressurized Enclosures Having Internal Source of Flammable Gas or Vapor
    • Pressurized Analyzer Rooms Containing a Source of Flammable Gas, Vapor, or Liquid

    To make the Standard more enforceable by states and jurisdictions, changes to the 2017 edition remove unenforceable language such as near, close to, and significant portion, because these terms cannot be quantified in the design or evaluation of an installation designed to NFPA 496 specifications. (Print, 28 pp., 2017)

     

    Interested in other editions of NFPA 496? Use the drop down menu above to select the edition year you need.

  • Table of Contents (2017 Current Edition)

    NFPA® 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment, 2017 Edition

    Chapter 1 Administration
    1.1 Scope.
    1.2 Purpose.
    1.3 Application.
    1.4 Equivalency.
    1.5 Units of Measurement.
    1.6 Mandatory Rules, Permissive Rules, and Explanatory Material.
    Chapter 2 Referenced Publications
    2.1 General.
    2.2 NFPA Publications.
    2.3 Other Publications.
    2.4 References for Extracts in Mandatory Sections.
    Chapter 3 Definitions
    3.1 General.
    3.2 NFPA Official Definitions.
    3.3 General Definitions.
    3.4 NEC Extracted Definitions.
    Chapter 4 General Requirements for Pressurized Enclosures
    4.1 Applicability.
    4.2 Suitability of Identified Equipment.
    4.3 Enclosure.
    4.4 Pressurizing System.
    4.5 Protective Gas System.
    4.6 Determination of Temperature Marking.
    4.7 Ventilated Equipment.
    4.8 Power Equipment.
    4.9 Type Z Pressurizing.
    4.10 Type Y Pressurizing.
    4.11 Type X Pressurizing.
    4.12 Markings.
    Chapter 5 Pressurized Enclosures for Class I
    5.1 Applicability.
    5.2 General Requirements.
    5.3 Markings.
    5.4 Additional Requirements for Type Y or Type Z Pressurizing.
    5.5 Additional Requirements for Type X Pressurizing.
    Chapter 6 Pressurized Enclosures for Class II
    6.1 Applicability.
    6.2 General Requirements.
    6.3 Markings.
    6.4 Marking Information.
    6.5 Additional Requirements for Type X Pressurizing.
    6.6 Additional Requirements for Ventilated Equipment.
    Chapter 7 Pressurized Control Rooms
    7.1 Applicability.
    7.2 Protective Gas.
    7.3 Considerations Relating to Positive Pressure Ventilation.
    7.4 Requirements for Positive Pressure Air Systems.
    Chapter 8 Pressurized Enclosures Having an Internal Source of Flammable Gas or Vapor
    8.1 Applicability.
    8.2 General Requirements.
    8.3 Specific Requirements.
    Chapter 9 Pressurized Analyzer Rooms Containing a Source of Flammable Gas, Vapor, or Liquid
    9.1 Applicability.
    9.2 General.
    9.3 Specific Requirements.
    Annex A Explanatory Material
    Annex B Informational References
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