Ex Zones or Hazardous Area Zones are classified on the basis of the frequency and duration of the presence of an explosive atmosphere. Gases, vapours and mists.
- Zone 0 is an area in which an explosive atmosphere in the form of gas, vapour or mist is present continuously or for long periods of time.
- Zone 1 is an area in which an explosive atmosphere in the form of gas, vapour or mist is present occasionally.
- Zone 2 is an area in which an explosive atmosphere in the form of gas, vapour or mist is present for a short period of time only.
For dusts, the zone classifications are:
- Zone 20 A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently.
- Zone 21 A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.
- Zone 22 A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
Layers, deposits and heaps of combustible dust must be considered as any other source which can form
an explosive atmosphere. “Normal operation” means the situation when installations are used within their design parameters.
