Hazardous locations according to the NEC code

In North America the standard reference documents for electrical installations are the National Electric Code (NEC) for the USA and the Canadian Electrical Code (CEC) for Canada.

Electrical Equipment used in Ordinary, Wet and Hazardous (or Classified) Locations must be 'listed' by an accredited approval agency for use in the intended location. The hazardous locations include areas in which flammable, combustible or ignitable substances may occur in hazardous amounts. The NEC and CEC codes allow two methods of categorising Hazardous Locations, which are Class and Division, and Class and Zone.

Electrical Apparatus approved for use in Hazardous Locations must be categorised with an Equipment Class and suitable for a specified Division and Gas Group. Their classification is made in line with the amount of combustible materials as :-

Class I - Flammable gases, vapours or mists
Class II - Combustible Dusts
Class III - Ignitable Fibres and Flyings

A similar arrangement of categorising Gas Groups is used in the North American / Canadian standards as in IEC standards although the identification of Gas Groups is different. eg. :-

Division Definitions : Division 1 or Division 2

Equipment Classified : Class I, Division 1, A B C D