NFPA Issues 2017 Edition of NFPA 499

Earlier this year, NFPA issued the 2017 edition of NFPA 499: Recommended Practices for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. While “Chemical Process Areas” is identified in the title of the standard, the standard applies to chemical processing or mixing operations, which can include agricultural dusts, if mixing is occurring.The standard is a useful tool in classifying combustible dust areas as part of a Dust Hazard Analysis (DHA) as required by NFPA 652: Standard on the Fundamentals of Combustible Dusts. The classification diagrams that have been included are particularly useful in determining the extent of rated locations for typical dust mixing/handling operations.

With this 2017 revision, a major update is the inclusion of the Zone classification system per Article 506 of NFPA 70: National Electric Code. Previous editions of this standard explicitly did not apply to the use of Zone classification systems. The definitions for the Zone classification system are pulled from Article 506, which aligns with the European ATEX Zone classification system. This is an important update for foreign corporations utilizing the European ATEX Zone classification system for their U.S. facilities, especially as Canada is moving away from the Class, Division system and into the Zone system. Also updated in this revision is guidance for Class III combustible fibers and flyings.

For the purposes of the standard, Zones 20 and 21 are combined with Class II, Division 1 for determining area locations and Zone 22 is combined with Class II, Division 2. The diagrams for classifying combustible dust locations have been updated to include diagrams under the Zone classification and for Class III locations.

The standard is available for purchase or free online viewing on NFPA’s website: If you have questions about how this NFPA update affects your facility, please do not hesitate to contact CTI.

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