Every year, numerous ATEX-related accidents occur at high-risk industrial sites. These accidents are often the result of a lack of awareness of the dangers associated with potentially explosive atmospheres, and a lack of preventive and protective equipment.
However, ATEX zones are now covered by European directives. These allow facility managers to take preventive action to avoid their occurrence.
How are explosive atmospheres formed? In what type of industry are they found? What are the most common sources of ignition?
What is ATEX?
General
An ATEX (or ATmosphère EXplosible) is an atmosphere where one or more explosions can potentially take place.
An explosion, on the other hand, consists of a very rapid increase in volume and release of energy, with the generation of high temperatures and gases.
It can be of physical origin, due to the bursting of an element whose internal pressure is unsustainable, or chemical, in the latter case resulting from a chemical reaction.
Gases, vapors and flammable dusts contain unstable compounds that can cause explosions, and these risks can be prevented bypurchasing ATEX equipment.
In accordance with EN 1127 – 1an explosion is a sudden oxidation or decomposition reaction involving a rise in temperature or pressure, or both simultaneously.
Conditions
For ATEX to exist, three conditions must be met:
- Presence of an oxidizer. This is generally air.
- Presence of a combustible. Flammable substances are gases, vapors or dusts.
- A source of ignition or very high temperature. The most frequent sources of ignition are static electricity, lightning, open flames, mechanical sparks, hot surfaces, etc.
These three conditions form what is commonly known as the fire triangle.
Where can you find ATEX?
Technically, all industries using flammable substances (gases, dusts, vapors) present an explosion risk.
They are therefore subject to ATEX regulations.
These include high-risk industrial sites (SEVESO), as well as metal processing plants, paint shops, flour silos, wood processing plants, refineries and even waste recycling centers…
How to avoid ATEX?
There are two main regulatory texts concerning ATEX.
- The first is aimed at plant managers (Directive 99/92/EC) and sets out all the minimum health and safety requirements for personnel likely to be exposed to ATEX.
- The second text is aimed at manufacturers (Directive 94/0/EC) and lays down the minimum safety requirements for ATEX protection equipment and systems.
When it comes to detecting, determining and classifying ATEX zones, plant managers must comply with the requirements of standard NF EN 60079-0-1.
We also need to classify the hazardousness of flammable substances and carry out an occupational and technological risk assessment.
ATEX glossary: what to remember?
Flash point of a flammable liquid: Temperature at which a liquid gives off enough vapor to form a flammable mixture with air.
Note: Some substances have their flash point at negative temperatures.
- MIE (Minimum Ignition Energy): Minimum energy that must be supplied to the mixture, in the form of a flame or spark, to cause ignition.
It is expressed in Joules (for example, the spark from a spark plug is about 1J).
- IEMS (Interstice Expérimental Maximal de Sécurité) : Maximum thickness of the layer of air between 2 parts of an internal chamber of a test Apparatus which, when the internal mixture is ignited, prevents ignition of the same external gas mixture through a shoulder 25 mm long.
Would you like to learn more about the risk of explosion to protect yourself?
ADF Systèmes makes it a point of honor to help you choose the products and solutions best suited to your industrial safety and risk management needs. To find out more about ESD risks, download our guide to earthing.
