Technical Information and Requirements

Area Classification Systems

North America

In North America, hazardous locations have traditionally been defined by the following combination of Class and Division:

Class I - A location where a quantity of flammable gas or vapor, sufficient to produce an explosive or ignitable mixture, may be present in the air.

Class II - A location made hazardous by the presence of combustible or electrically conductive dust, including Groups E (metal dust), F (coal dust) and G (grain dust).

Class III - A location made hazardous by the presence of easily ignitable fibres or flyings in the air, but not likely in sufficient quantities to produce ignitable mixtures.

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Division 1 - A location where a classified hazard is likely to exist.

Division 2 - A location where a classified hazard does not normally exist but is possible under abnormal conditions.

For example: In Class I, Division 1, flammable gases or vapors could exist in quantities sufficient to produce an explosive or ignitable mixtures under normal operating conditions; in Class I, Division 2, flammable volatile liquids are normally confined within closed containers from which they can only escape as a result of accidental rupture.

International

Internationally (and more recently in North America, for Class I hazardous locations), areas where explosive gas atmospheres are likely to be present are divided into three IEC-defined Zones:

Zone 0 - An area in which an explosive gas atmosphere is continuously present or present for long periods.

Zone 1 - An area in which an explosive gas atmosphere is likely to occur in normal operation.

Zone 2 - An area in which an explosive gas atmosphere does not normally exist.

For exact definitions, see the Canadian Electrical Code, available from CSA. To order the Code, visit our On-line Store.

Area Classification - Division versus Zone

Comparing Divisions versus Zones

Division 1 corresponds closely to Zones 0 and 1. Division 2 corresponds closely to Zone 2. The most important difference between the Division and Zone systems i the difference in marking conventions. Division markings identify the locations where the product could be used. The markings for the Zone method show the type of protection, according to IEC 60079 Series standards-for example, "ia" (intrinsic safety) or "d" (flameproof).

Learn more today:

Methods of Protection Area Classificiation Systems Summary of commonly used protection methods for different div. & zones Apparatus Grouping Temperature code & Temperature class Testing Facilities Standards and Protection