 ATEX is the name commonly given to the two European Directives for controlling explosive atmospheres: 1) Directive 99/92/EC (also known as ‘ATEX 137′ or the ‘ATEX Workplace Directive’) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres.
Specifications:
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An explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.
Gases, vapours, mists and dusts can all form explosive atmospheres with air. Hazardous area classification is used to identify places where, because of the potential for an explosive atmosphere, special precautions over sources of ignition are needed to prevent fires and explosions.
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Classification of an area
Hazardous areas are divided into Zones (European and IECEX method) or Classes and Divisions (North American method) according to the likelihood of a potentially explosive atmosphere being present.
European & IECEX classification | Definition of zone or division | North American classification |
Zone 0 (gases) | An area in which an explosive mixture is continuously present or present for long periods | Class I Division 1 (gases) |
Zone 20 (dusts) | Class II Division 1 (dusts) | |
Zone 1 (gases) | An area in which an explosive mixture is likely to occur in normal operation | Class I Division 1 (gases) |
Zone 21 (dusts) | Class II Division 1 (dusts) | |
Zone 2 (gases) | An area in which an explosive mixture is not likely to occur in normal operation and if it occurs it will exist only for a short time | Class I Division 2 (gases) |
Zone 22 (dusts) | Class II Division 2 (dusts) |
Product marking
The ATEX directive requires the product to be marked with the CE mark, the ‘EX’ mark and the
equipment coding as per table below.
Heading | Mark | Use |
Explosion proof | Â | in accordance with the ATEX directive |
Equipment Group | I | For use in underground mines |
II | For use in all other places | |
Category | 1 | Equipment that is intended for use in areas where an explosive atmosphere is present continuously, for long periods or frequently |
2 | Equipment that is intended for use in areas where an explosive atmosphere is likely to occur in normal operation and must ensure a high level of protection. | |
3 | Equipment that is intended for use in areas where an explosive atmosphere is unlikely to occur in normal operation and must ensure a normal level of protection. | |
Gas / Dust | G | Equipment certified for use in flammable gases |
D | Equipment certified for use where dust is present in the atmosphere | |
Type of Protection* | d | Flameproof |
Ia | Intrinsically Safe | |
e | Increased safety | |
Gas Group | I | Mines |
II | Surface above ground industries | |
Gas Sub Group | A | Less easily ignited gases e.g. propane |
B | Easily ignited gases e.g ethylene | |
C | Most easily ignited e.g. hydrogen or acetylene | |
Temperature Classification | T1 | 450ºC |
T2 | 300ºC | |
T3 | 200ºC | |
T4 | 135ºC | |
T5 | 100ºC | |
T6 | 85ºC |
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Product marking example
An ATEX approved electrical product is marked with the following code:
| II 2G Eexd IIB T4 |
From the breakdown of the code below it can be seen that the product is flameproof, suitable for use in zone 1 surface applications where gas group B gases may be present and the surface temperature of the product under fault conditions will not exceed 135 ºC.
 | Explosion proof in accordance with ATEX |
II | Equipment group: II surface industries. |
2 | Category: 2 equipment ( suitable for use in Zone 1) |
G | Gas / Dust: Suitable for atmospheres containing gas |
E | European certificate in accordance with harmonised standards |
Ex | Explosion-proof electrical equipment |
d | Type of protection is ‘Flameproof enclosure’ |
II | Gas Group II – surface industries |
B | Gas sub group = B |
T4 | Temperature class T4 |
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