– Zone 0: An area where an explosive atmosphere, consisting of a mixture with air of flammable substances in the form of gas, vapour, or mist, is present continuously, for long periods, or frequently.

– Zone 1: An area where an explosive atmosphere, consisting of a mixture with air of flammable substances in the form of gas, vapour, or mist, is likely to occur occasionally under normal operating conditions.

– Zone 2: An area where an explosive atmosphere, consisting of a mixture with air of flammable substances in the form of gas, vapour, or mist, is not likely to occur in normal operations; however, if it does occur, it will persist for only a short duration.

For dusts, the classifications are as follows:

– Zone 20: An area where an explosive atmosphere, in the form of a cloud of combustible dust in air, is present continuously, for long periods, or frequently.

– Zone 21: An area where an explosive atmosphere, in the form of a cloud of combustible dust in air, is likely to occur occasionally under normal operating conditions.

– Zone 22: An area where an explosive atmosphere, in the form of a cloud of combustible dust in air, is not likely to occur in normal operations; however, if it does occur, it will persist for only a short duration.