International (IEC) and European (CENELEC) Zone Areas

The International Standard IEC 60079-10 defines the guidelines for classifying hazardous areas into zones based upon the frequency of the occurrence and duration of an explosive gas atmospheres.

Zone 0 An area in which an explosive gas atmosphere is present continuously or for long periods . ( Rough Guide : More than 1 , 000 hours / year )
Zone 1 An area in which an explosive gas atmosphere is likely to occur in normal operation . ( Rough Guide: 10 hours or more / year but less than 1,000 hours / year)
Zone 2 An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it does occur, is likely to do so only infrequently and will exist for a short period only . ( Rough Guide : Less than 10 hours / year )
Zone 20 An area in which combustible dust, as a cloud, is present continuously or frequently, during normal operation, in sufficient quantity to be capable of producing an explosive concentration of combustible dust in a mixture with air.
Zone 21 An area, in which combustible dust, as a cloud, is occasionally present during normal operation, in a sufficient quantity to be capable of producing an explosive concentration of combustible dust in a mixture with air.
Zone 22 An area, in which combustible dust, as a cloud, may occur infrequently and persist for only a short period, or in which accumulations of layers of combustible dust may give rise to an explosive concentration of combustible dust in a mixture with air.
The European Committee for Electrotechnical Standardization (CENELEC)
Due to the different standards for equipment used in hazardous locations had effect of creating trade barriers within the European Community . Then, the members of the European Community decided to establish uniform standards for hazardous location apparatus and to accept each other's product certificates The harmonized European Standards were developed by CENELEC, based on IEC recommendations, are called EN European Standard ( Europaische Norm).

International - IEC / CENELEC Standards
Protection Techniques