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2. Definitions
2.1 Explosive gas atmosphere: A mixture with air, under atmospheric conditions, of a flammable material in the form of a gas or vapour in which, after ignition, combustion spreads throughout the unconsumed mixture
NB - Although a mixture which has a concentration above the upper explosive limit (UEL) is not an explosive gas atmosphere, it can readily become so and, in certain cases for area classification purposes, it is advisable to consider it as an explosive gas atmosphere.
2.2 Hazardous area: An area in which an explosive gas atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of apparatus. Hazardous areas are classified into one of three zones, 0, 1 and 2, depending on the frequency and duration of an explosive gas atmosphere occurring.
2.3 Operator: The person who will operate the equipment from day to day
2.4 User: The organisation that has purchased and installed the equipment, and whose employees will operate it.
2.5 Zone 0: An area in which an explosive gas atmosphere is present continuously or for long periods (this is defined as more than 1000 hours per year). Example: At the spray gun tip before/after ignition or when the flame goes out.
2.6 Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation (this is defined as less than 1000 hours, but more than 10 hours per year). Example: Inside the spray booth. The immediate area around the flammable gas stores.
2.7 Zone 2: An area in which an explosive
gas atmosphere is not likely to occur in normal operation and, if it does
occur, is likely to do so only infrequently and will exist for a short
period only (this is defined as less than 10 hours per year). Example:
The area around a flange, connection or other pipe fitting that is not
expected to release flammable material during normal operation.