Codes and standards published by NFPA are displayed as read-only under license from NFPA solely for use within this system. NFPA material may not be downloaded, printed, reproduced, or transferred.

Follow the 2010 NFPA 91 to prevent exhaust systems from spreading fire and increasing explosion risks.

NFPA 91: Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible 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.

Key changes in the 2010 Standard include:

* Updated definitions for consistency with other particulate solids documents, such as NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particular Solids
* Amended scope and application clarify that the provisions are intended to provide protection against fire and explosion hazards.
* Revised requirements pertaining to access to ducts for purposes of inspection provide a more performance oriented approach.
* New chapter on air-material separators based on provisions in NFPA 654
* Modified testing and maintenance rules require that provisions be applicable retroactively. This is consistent with the other particulate solids documents, such as NFPA 654.
* Revised requirements for duct clearances from combustible construction include more comprehensive criteria for various installations of duct systems.

The 2010 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; design engineers; fire protection engineers; safety and health professionals; industrial hygienists; and fire and building officials.