2021 NFPA 497 Recommended Practice - Current Edition
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  • Description

    Stay on top of safety in chemical process, storage, and handling areas with the updated NFPA 497, 2021 edition.

    The release of flammable, combustible substances into an atmosphere with electrical systems or equipment can result in a potentially deadly and destructive incident. NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, delivers broad-based requirements for better safeguarding locations that handle these substances.

    This vital safety document offers recommended practices that provide a basic understanding of parameters used to classify the extent of a hazardous location. You get criteria for assessing ignitability hazards in chemical process areas, as well as provisions for selecting the appropriate electrical systems and equipment for optimal safety.

    NFPA 497 is a must-have guideline for:

    • Installers and maintainers of electrical equipment located in or near areas where flammable or combustible liquids or flammable gases or vapors are present
    • Equipment manufacturers providing equipment suitable for use in applicable electrically classified areas
    • Design engineers, consultants, loss prevention or safety engineers, insurance professionals, enforcing officials, and owners/operators of industrial facilities

    The revised NFPA 497 is updated to reflect current industry knowledge and remain consistent with related codes and standards.

    The 2021 edition of these recommended practices work in conjunction with NFPA 70, National Electrical Code® (NEC®), to factor ignitability hazards and relevant electrical systems and components.

    Additional notable changes for 2021 include:

    • A revised Table 4.4.2 to update chemical and physical property data based on the Design Institute for Physical Properties (DIPPR) database
    • Updated Table 4.4.3 to correlate with Table 4.4.2

    Be prepared to meet minimum safety requirements for areas using ignitible gases and liquids.

    Make sure you have the latest information for helping to protect lives and property in industrial facilities by placing your order for NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.

  • Table of Contents (2021 Current Edition)

    NFPA® 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 2021 Edition

    Chapter 1 Administration
    1.1 Scope.
    1.2 Purpose.
    1.3 Relationship to NFPA Codes and Standards.
    Chapter 2 Referenced Publications
    2.1 General.
    2.2 NFPA Publications.
    2.3 Other Publications.
    2.4 References for Extracts in Recommendations Sections.
    Chapter 3 Definitions
    3.1 General.
    3.2 NFPA Official Definitions.
    3.3 General Definitions.
    Chapter 4 Classification of Combustible Materials
    4.1 National Electrical Code Criteria.
    4.2 Behavior of Class I (Combustible Material) Gases, Vapors, and Liquids.
    4.3 Conditions Necessary for Ignition.
    4.4 Classification of Class I Combustible Materials.
    Chapter 5 Classification of Class I (Combustible Material) Areas
    5.1 National Electrical Code (NEC).
    5.2 General.
    5.3 Class, Division, Classified Locations.
    5.4 Zone Classified Locations.
    5.5 Unclassified Locations.
    5.6 Extent of Classified Locations.
    5.7 Discussion of Diagrams and Recommendations.
    5.8 Basis for Recommendations.
    5.9 Procedure for Classifying Locations.
    5.10 Classification Diagrams for Class I, Divisions.
    5.11 Classification Diagrams for Zones.
    Annex A Explanatory Material
    Annex B Example of a Method for Determining NEC Group Classification for Mixtures
    Annex C Informational References
  • 2017 Edition Description

    2017 Edition

    Use NFPA 497 hand-in-hand with the new NEC® to determine ignitability hazards and select electrical systems and equipment for safe use in Class I hazardous (classified) locations.

    In places where flammable gases or vapors, flammable liquids, or combustible liquids are processed or handled, their release into the atmosphere could result in their ignition by electrical systems or equipment. Work with today's best practices to address potentially deadly and destructive hazards with the 2017 edition of NFPA 497, Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.

    This important Recommended Practice also provides information on specific flammable gases and vapors, flammable liquids, and combustible liquids whose relevant combustion properties have been sufficiently identified to allow their classification into the groups established by NFPA 70®, National Electrical Code® for proper selection of electrical equipment in hazardous locations.

    NFPA 497 keeps pace with new knowledge. Updated references and definitions extracted from other NFPA® codes include:

    • The 2017 edition of the National Electrical Code
    • The 2016 edition of NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG)
    • The 2015 edition of NFPA 30, Flammable and Combustible Liquids Code

    Other changes and edits improve usability and provide consistency with related codes and standards.

    NFPA 497 is an essential on-the-job tool for installers and maintainers of industrial equipment using electrical power that is to be located in or near areas where flammable or combustible liquids, or flammable gases or vapors are stored, handled, or used; equipment manufacturers providing equipment suitable for use in such electrically classified areas; design engineers/consultants; loss prevention or safety engineers; insurance professionals; enforcing officials; and owners/operators of industrial facilities. (Print, 76 pp., 2017)

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