Last edit: 03/03/2023
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.
– 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 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.
– 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 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.
– 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.
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.