The presence of combustible dusts in industrial settings where electrical systems and equipment are used represents a significant ignition hazard. NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, provides guidance for selecting electrical systems for safe use in Class II hazardous (classified) locations in accordance with relevant codes and standards.

This essential safety document delivers criteria for designating classified areas where combustible dusts are produced, processed, or handled. NFPA 499 is a must-have for:

• Anyone responsible for hazardous area classification in industrial facilities
• Facility operators, installers, and maintainers of electrical equipment used in areas where combustible dusts are present
• Owners or operators of industrial facilities, insurance professionals, AHJs, and enforcing officials
• Manufacturers of equipment for use in electrically classified process areas
• Design engineers/consultants, loss prevention or safety engineers

This recommended practice offers detailed guidelines, classification diagrams, and dust group classifications on an extensive list of combustible dusts.

 2024 edition revisions include:

• Revised Section 4.2 to include a dust combustibility screening step to assess whether a dust poses a fire or flash-fire hazard if it is not considered combustible based on ASTM E1226 testing.
• Revisions have been made to allow the zone system to be used for layer ignition hazards.
• The definition for hazardous (classified) locations has been added from the NEC