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Classification of Hazardous Areas

Under the ATEX Directive 99/92/EC, users are required to assess the risk of explosions on their site and make a classification of risk zones. There are three types of areas according to the likelihood of forming an explosive mixture, and two different applications depending on the nature of the mixture (gas or dust).

 Hazardous_Areas

These regions must take account of external parameters (ventilation, openings, heating …) that can alter the extent of areas. The illustration below shows an example of classification of hazardous areas for unloading station flammable liquid. The principle is the same for dust, only the name will change to zone 20, 21, 22. Beyond the Zone 2 or 22, there is more probability of occurrence of explosive mixture, it is “out of area classified” and it is possible to use standard industrial equipment.

zone

Notes:
– Device certified for Zone 0 could also be used in zones 1 and 2.
– Device certified for Zone 22 could not be used in zone 20 or 21.
– The area 0 (within a vessel) and the zone 20 (inside a silo) are areas where there is a fixed electrical equipment (except the sensors).
– Device certified for Zone 21 could not be used in zone 1.
Devices certified “GAS” (including devices increased safety “e”) ATEX are protected in their shell but also at each internal component.
However, the ATEX certified material “DUST” is protected at its outer envelope. However, there are many devices with dual certification “GAS” and “DUST” that can be used interchangeably in both types of environment.