NFPA 499

Abstract

Scope: This recommended practice provides information on the classification of combustible dusts and of hazardous (classified) locations for electrical installations in chemical process areas and other areas where combustible dusts are produced or handled. This recommended practice provides information on combustible dusts as it relates to the proper selection of electrical equipment in hazardous (classified) locations in accordance with NFPA 70 . The tables of selected combustible dusts contained in this document are not intended to be all-inclusive. Purpose. The purpose of this recommended practice is to provide the user with a basic understanding of the parameters that determine the degree and the extent of the hazardous (classified) location. This recommended practice also provides the user with examples of the applications of these parameters. This recommended practice is intended as a guide and should be applied with sound engineering judgment. Where all factors are properly evaluated, a consistent area classification scheme can be developed. This recommended practice is based on the criteria established by Articles 500 and 502 of NFPA 70 . The application of this recommended practice does not address all potential hazards associated with solid particulate materials, including, but not limited to, the possible need for explosion venting or explosion suppression addressed in other NFPA standards. This recommended practice provides guidance for classification of Class III or Group IIIA combustible fibers/flyings and of hazardous (classified) locations where these present a dust fire or dust explosion hazard when dispersed and ignited in air.