ATEX classifications of equipment
The ATEX (Explosive Atmospheres) equipment classification is a classification method used to determine the level of protection required for equipment used in potentially explosive areas.
This classification is based on the probability of the presence of an explosive atmosphere and the duration for which this atmosphere may be present. It is used to determine the appropriate ATEX equipment category for a given area.
There are two ATEX directives, ATEX 94/9/EC for equipment intended for use in potentially explosive atmospheres, and ATEX 99/92/EC for the minimum requirements for the protection of workers exposed to the risk of explosive atmospheres.
ATEX classification is important to ensure the safety of workers in potentially hazardous environments and to prevent explosions and fires. ATEX equipment must be designed and manufactured in accordance with specific safety standards, tested and certified before being used in areas at risk of explosion.
Classification of equipment for use in ATEX zones
| CLASSIFICATION OF DANGEROUS AREAS | EUROPEAN/IEC CLASSIFICATION | |||
|---|---|---|---|---|
| Substances flammable | Temporary behavior of flammable substances in hazardous locations | Areas types | Equipment required for installation | |
| Equipment group | Hardware protection level | |||
| Gas Vapors | is present permanently, for long periods or frequently | Zone 0 | II | Ga |
| is likely to occur occasionally during normal operation | Zone 1 | II | Gb | |
| is not likely to occur during normal operation, or, if it does occur, is only of short duration | Zone 2 | II | Gc | |
| Dust | is present permanently, for long periods or frequently | Zone 20 | I | Yes |
| is likely to occur occasionally during normal operation | Zone 21 | I | Db | |
| is not likely to occur during normal operation, or, if it does occur, is only of short duration | Zone 22 | I | Dc | |
| Dust | - | Mines | III | My |
| - | Mines | III | Mb | |
| SUBDIVISION OF GASES AND VAPORS | ||||
|---|---|---|---|---|
| Equipment usable in the group | Gas or vapors | |||
| ammonia methane ethane propane | ethyl alcohol cyclohexane n-butane | n-hexane essence | acetaldehyde | |
| city gas, acrylonitrile | ethylene ethylene oxide | ethylene glycol | ethyl ether | |
| hydrogen | ethine (acetylene) | carbon disulfide | ||
According to the same principle as for gases and vapors, dusts are divided into 3 groups.
| DUST | |
|---|---|
| IIIA | Flammable volatiles |
| IIIB | Non-conductive dust |
| IIIC | Non-conductive dust |
Each type of dust has been the subject of detailed studies to determine their flammability characteristics (INRS brochures/Silos guide, etc.). The particularity of dust is that their auto-ignition temperatures differ depending on whether the dust is in clouds or layers. As many other parameters can modify these auto-ignition values (particle size, humidity, ambient temperature, etc.), a calculation integrating a safety margin must be carried out for each case.
| SPECIFIC EQUIPMENT CONDITIONS | |
|---|---|
| Requirements | Marking |
| Equipment without specific conditions | - |
| Equipment with special protection, may be marked | X |
| Ex component that requires additional certification before any use in hazardous areas | U |
Temperature classes
The flameproof enclosure must not have hot spots on its external surface that could cause self-ignition. Each device is classified according to the maximum surface temperature reached in service.
Summary table of temperature classes by gas
