NFPA 499: Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
Current Edition: 2013 Next Edition: 2017

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What is NFPA 499?
NFPA 499: Document Scope
1.1 Scope. 1.1.1 This recommended practice applies to those locations where combustible dusts are produced, processed, or handled, and where dust released into the atmosphere or accumulated on surfaces could be ignited by electrical systems or equipment. 1.1.2 This recommended practice provides information on specific combustible dusts whose relevant combustion properties have been sufficiently identified to allow their classification into the groups established by NFPA 70, National Electrical Code (NEC), for proper selection of electrical equipment in hazardous (classified) locations. The tables of selected combustible materials contained in this document are not intended to be all-inclusive. 1.1.3 This recommended practice also applies to chemical process areas. As used in this document, a chemical process area could be a chemical process plant, or it could be a part of such a plant. A chemical process area could be a part of a manufacturing facility where combustible dusts are produced or used in chemical reactions, or are handled or used in operations such as mixing, coating, extrusion, conveying, drying, and/or grinding. 1.1.4 This recommended practice does not apply to agricultural grain-handling facilities except where powdered grain is used in a chemical reaction or mixture. 1.1.5 This recommended practice does not apply to situations that could involve catastrophic failure of, or catastrophic discharge from, silos, process vessels, pipelines, tanks, hoppers, or conveying or elevating systems. 1.1.6 This recommended practice does not address the unique hazards associated with explosives, pyrotechnics, blasting agents, pyrophoric materials, or oxygen-enriched atmospheres that might be present.
This recommended practice presents criteria to determine ignitability hazards in chemical process areas where combustible dusts are produced, processed, or handled to assist in the selection of electrical systems and equipment for safe use in Class II hazardous (classified) locations. Official document scope
What does NFPA 499 address?
Data is provided on the classification of combustible dusts and hazardous (classified) locations for electrical installations as it relates to the proper selection of electrical equipment in such locations in accordance with NFPA 70: National Electrical Code. Coverage includes extensive data on physical properties of selected combustible dusts, including specific Class II, division, and dust group information. Table of Contents

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