2020 NFPA 91 Standard - Current Edition
In purchasing digital access through a PDF or subscription service, you are purchasing a single-user license to access content only by the named account holder. Certain restrictions apply.

NFPA Members save an additional 10%.

Item #: NFPA_91
Price: $0.00
Digital Access with NFPA LiNK® Plans starting at $11.99/month
Formats Available:

  • Description

    Help ensure compliance with critical requirements for safeguarding potentially dangerous exhaust systems from fires and explosions.

    For well over a century, NFPA® codes and standards have been addressing the inherent dangers that blower and exhaust systems can present to public safety. NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids, 2020 edition, represents the most complete criteria for designing, constructing, installing, testing, operating, and maintaining these systems.

    This vital safety document assists in protecting lives and property and minimizing loss from fires and explosions in exhaust systems where vapors, gases, mists, and particulate solids are present in the airflow. The standard incorporates provisions on the application of exhaust systems to specific industries or operations from NFPA 1, Fire Code, NFPA 30, Flammable and Combustible Liquids Code, and many other codes and standards.

    Update to the 2020 edition to access the most current information and performance criteria.

    The revised NFPA 91 provides the latest knowledge on exhaust systems for air conveying vapors, gases, mists, and particulate solids relating to fire and explosion prevention. Content covers everything from requirements for corrosive materials and air-moving devices to air-material separators, ignition sources, and fire protection systems.

    Changes to the 2021 edition include added requirements for nonconductive system components and revision to the concentration threshold for flammable or combustible materials requiring spark-resistant fans and blowers.

    NFPA 91 is an essential resource for process industries with ignition risks of materials pneumatically conveyed through duct systems.

    It is critical design and fire protection engineers, safety and health professionals, industrial hygienists, or fire and building officials have access to the most relevant codes and standards. Stay current and compliant by placing your order for NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids, 2020 edition.

  • Table of Contents (2020 Current Edition)

    NFPA® 91 Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids, 2020 Edition

    Chapter 1 Administration
    1.1 Scope.
    1.2 Purpose.
    1.3 Retroactivity.
    1.4 Equivalency.
    1.5 Units of Measurement.
    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.
    Chapter 4 Design and Construction
    4.1 Terminology.
    4.2 General Requirements.
    4.3 Duct Material and Construction.
    4.4 Access.
    4.5 Design Requirements.
    4.6 Hangers and Supports.
    4.7 Duct Installation.
    Chapter 5 Corrosive Materials
    5.1 General.
    Chapter 6 Air-Moving Devices
    6.1 General.
    6.2 Flammable or Combustible Materials.
    6.3 Clearance.
    6.4 Alignment.
    6.5 Maintenance and Inspection.
    6.6 Location.
    6.7 Flexible Connections.
    Chapter 7 Air–Material Separators (Air Separation Devices)
    7.1 General Requirements.
    7.2 Separators for Noncombustible Particulates.
    7.3 Separators for Flammable Gases, Vapors, and Mists.
    Chapter 8 Ignition Sources
    8.1 Electrical Equipment.
    8.2 Static Electricity.
    8.3 Manifolds.
    8.4 Open Flames and Sparks.
    8.5 Removal of Ferrous Materials.
    8.6 Belt Drives.
    8.7 Bearings.
    8.8 Equipment.
    Chapter 9 Fire Protection
    9.1 General.
    9.2 Drainage.
    9.3 Testing and Inspection.
    Chapter 10 Testing and Maintenance
    10.1 Retroactivity.
    10.2 General.
    10.3 System Test.
    10.4 System Inspection.
    10.5 Cleanliness.
    10.6 Maintenance Program.
    10.7 Maintenance Log.
    Annex A Explanatory Material
    Annex B Informational References
  • Prior Editions

    2015 Edition

    Comprehensive new 2015 NFPA 91 helps prevent exhaust systems from spreading fire and increasing explosion risks.

    Minimize the probability of a fire or explosion -- or loss from a fire or explosion -- with the 2015 edition of NFPA 91. Renamed to reflect a broader scope, NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids provides minimum requirements for the design, construction, installation, operation, testing, and maintenance of these systems except as modified or amplified by other applicable NFPA® standards.

    Changes reflect NFPA 91's expanded scope:

    • The Standard's new title and scope reflect that NFPA 91 is referenced for pneumatic conveying, duct design, and air moving device requirements within the commodity-specific combustible particulate and combustible dust standards.
    • Added definitions such as limited combustible and non-combustible were added for enhanced clarity and consistency with the 2013 NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particular Solids, along with other combustible dust documents.

    The 2015 NFPA 91 is essential for process industries in which there is production or release of gases, vapors, or solids that are pneumatically conveyed through duct systems. It's a must for design engineers, fire protection engineers, safety and health professionals, industrial hygienists, and fire and building officials. (Print, 22 pp., 2015)


    Interested in other editions of NFPA 91? Use the drop down menu above to select the edition year you need.

  • NFPA PDF Products

    If you purchased a PDF, licensed PDFs can be accessed immediately. Instructions can be found in your order confirmation.

    Effective with the annual 2020 code cycle, NFPA® will no longer offer access to the PDF format as a choice for new editions of codes and standards, handbooks, or other reference titles. Existing PDFs will remain in-market and will still be accessible in our National Fire Codes® Subscription Service (NFCSS™). For more information about the different format options available to access essential code and standard content you need, click here.

  • Historical Editions

    Previous editions of NFPA® documents are available for sale. Please see applicable NFPA codes and standards product pages to confirm which editions are available for purchase. If you have any questions, contact NFPA Customer Support at 1-800-344-3555 or nfpa.org/customerservice.