Practical considerations of area classification-how far to classify

Defining the classification of a location or facility (Class, Group, and Division), while often a difficult and time consuming task, is only the first of three separate and distinct tasks that must be performed by those who provide Electrical Area Classification. This first task defines the kinds of materials that are present in the location using the terms Class, Group, and Division. Both Article 500 of the National Electrical Code (NEC) and The American Petroleum Institute´s “Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities”-ANSI/API RP 500 (RP 500) are used in this task. The second task is to choose electrical equipment and installation techniques appropriate to the Class, Group, and Division decisions assigned to the location in the first task; the NEC is principally used in this task. The third and final task in Electrical Area Classification is to determine the physical boundaries or extent of the areas that are influenced by the Class, Group, and Division decisions reached in the first task. The NEC and RP 500 are both used in this final task of Electrical Area Classification. This paper concentrates on the methods used in the third task to determine the physical boundaries or extent of classified areas