ATEX 137 - Classification of Hazardous Areas

In accordance with the 1999/92/EC Directive, hazardous areas are classified as:

A place in which an explosive atmosphere consisting of a mixture with air or flammable substances in the form of gas, vapour or mist is:

• Zone 0 (Category 1 equipment)

present continuously or for long periods or frequently

• Zone 1 (Category 1 or 2 equipment)

likely to occur in normal operation occasionally

• Zone 2 (Category 1, 2 or 3 equipment)

not likely to occur in normal operation but, if it does occur, will persist for a short period only

A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is:

• Zone 20 (Category 1 equipment)

present continuously or for long periods or frequently

• Zone 21 (Category 1 or 2 equipment)

likely to occur in normal operation occasionally

• Zone 22 (Category 1, 2 or 3 equipment)

not likely to occur in normal operation but, if it does occur, will persist for a short period only

It is worth noting that ATEX maintenance and repair obligations depend on the category of the equipment rather than the zone in which it is installed. Therefore, putting Category 1 equipment, which has a very high level of safety and is designed for use in Zone 0 or Zone 20 areas, into a Zone 2 area could have long-term financial implications.