Last edit: 17/07/2025
The classified zone (also called ATEX zone) is A PHYSICAL VOLUME PART OF A MACHINE/IMPLOYMENT OR WORK AREA (it can be the inside of a tank, silo, an area outside a machine, the surroundings of a pipeline) where THE PROBABLE PRESENCE OF POTENTIALLY EXPLOSIVE ATMOSPHERE (air+gas/vapours or air+dust or air+gas/vapours+dust) HAS BEEN ASSESSED AND/OR CALCULATED (applying appropriate methodologies and recognised standards).
Areas are classified as follows:
– Zone 0: A place in which an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapour or mist is present continuously or for long periods or frequently.
A ‘practical example of zone 0 are areas inside containers of gasoline or other potentially explosive substances in containment areas. In those zones given the physical presence of the substance there is a high percentage of potentially flammable and explosive vapors.
– 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.
A practical example of zone 20 are fine powder storage areas such as flour, sugar, or sawdust warehouses
– Zone 1: A place in which an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapour or mist is likely to occur in normal operation.
Some examples of zone 1 are areas adjacent to piping of distribution systems for substances that generate potentially flammable and explosive vapors, more specifically in those areas that are confined, for example by a booth.
– 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.
Some examples of zone 21 are those areas adjacent to dust distribution or filtration systems, which generate potentially explosive and flammable vapors, which as in the case of gases are contained in confined areas.
– Zone 2: A place in which an explosive atmosphere consisting of a mixture of air and flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
Examples of zone 2 are all those areas adjacent to potentially explosive gas transportation systems, the presence of which is restricted.
– Zone 22: A place in which an explosive atmosphere in the form of a cloud of combustible dust is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
As in the case of zones 2, zones 22 are all those areas adjacent to potentially explosive dust transport systems, the presence of which is restricted.
Electrical installations in Zones 0-20 and 1-21 must be inspected every two years. Electrical installations in Zones 2-22 are NOT subject to periodic inspections.
GENERAL CLASSIFICATION PROCEDURE
The general procedure for classifying an ATEX Zone and thus establishing its hazardousness and the suitable equipment to be used inside it is as follows:
– Study of the processed substances: chemical and physical characteristics of the substances, maximum temperatures and pressures at which the substances are found, how they are used in the production process, etc.
– Environmental study: assuming local geometric characteristics, ventilation characteristics of rooms and machines, ambient temperatures and pressures, etc.
– Identification and analysis of emission sources: establish the degree of emission of the sources. That is, studying the ways and quantities in which substances are emitted.
– Classification of the type of Zone: based on the procedures suggested by the standards, identification of the type, shape and extent of the hazardous zones.