ATEX: how to prevent the risk of explosion in the workplace?

According to INRS, there is an explosion in the French industrial sector every day. The consequences can be very serious, in terms of both human lives and property. To limit the risk, specific regulations, known as "ATEX", have been put in place. Risk assessment, delimitation of ATEX zones, etc. We take a look at the main regulatory requirements.

Explosion risk: what does "ATEX" mean?

The acronym " ATEX" for explosive atmosphere is generally used to describe the risk of explosion in the workplace. An explosive atmosphere is a workplace where there is a risk of explosion due to the presence of flammable and combustible and combustible materials.

Consequently, any company storing or using combustible or flammable products is potentially exposed to the risk of explosion, and must comply with the applicable regulations.

Unlike a fire, an explosion is an almost instantaneous combustion that takes place after the formation of an ATEX. An explosive atmosphere is defined as a mixture of air and combustible substances (dust, solvent values, etc.).

For an explosion to occur, six conditions must be met simultaneously. These are illustrated in the diagram below:

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Please note: containment is not a prerequisite, but an aggravating factor in the explosion phenomenon.

Explosion risk: what are the employer's obligations?

Assessing the risk of explosion

As with all occupational hazards, the employer must assess the explosion risk. The first step is to identify hazards by means of a functional analysis:

• Draw up an inventory of combustible products and their characteristics (density, flash point, chemical incompatibilities with other products, etc.), as well as their quantities and storage conditions;
• Analyze the processes implemented through a precise study of the installations and workstations;
• Study potential malfunctions: it may be useful to draw on feedback from the company or industry to highlight any incidents or obstacles to "normal" operation.
• Identify sources of ignition : all sources of ignition are detailed in standard NF EN 1127-1. These may include electrical sources (sparks, heating, etc.), electrostatic sources (spark discharges, etc.) or thermal sources (cigarettes, hot-spot work, etc.).

Caution: risk assessment must be carried out in a global manner i.e. by combining it with the results of assessments of other occupational risks identified in each of the company's work units.

The risk assessment must then enable the employer toidentify zones where explosive atmospheres may form. The purpose of zoning is twofold:

• Materialize the risk by marking ATEX zones and workplaces with ATEX zones with the regulatory pictogram;
• Match all electrical and non-electrical equipment to the type of zone.

An order dated July 8, 2003 defines the classification of locations where explosive atmospheres (ATEX) may occur, and the minimum requirements to be met.

Caution: layers, deposits and heaps of combustible dust must be considered as sources likely to form an explosive atmosphere.

Regulations do not precisely define the terms " frequently " and " occasionally". However, companies can refer to the definitions adopted by certain professional bodies (Union des industries chimiques, Groupe d'étude de sécurité des industries pétrolières):

• Zone 0 or 20: duration of ATEX > 1000 hours / year ;
• Zone 1 or 21: duration of ATEX occurrence between 10 and 1000 hours / year ;
• Zone 2 ou 22 : durée d’apparition de l’ATEX < 10 heures / an.

The results of the risk assessment must be recorded in the Explosion Protection Document (EPD).

Implement technical and organizational measures

Based on the results of the risk assessment, prevention and protection measures must be put in place. Their aim must be to :

• First and foremost, toprevent the formation of explosive atmospheres by acting on the combustibles and oxidizer. Examples: increasing particle size, capturing vapors and dusts at source, introducing an inert gas to deplete the atmosphere of oxygen, etc.

• If the activity cannot prevent the formation of ATEX, avoid sources of ignition by taking action on processes and equipment, as well as by carrying out controls. Examples: installation of cooling systems, adaptation of installations, etc.

• Limit the effects of an explosion, for example by installing explosion vents or suppressors, or by modifying the configuration and design of the premises. Examples: compartmentalization, choice of suitable fire-resistant materials, etc.

More generally, employers must ensure that workers in ATEX zones can work in complete safety. In particular, he must take the necessary measures to ensure that :

• Personnel working in ATEX zones must be trained in explosion risk: this training must be tailored to the worker's level of exposure;
• Adequate supervision is ensured;
• Workers are equipped with appropriate clothing to protect against the risk of ignition;

Please note: the measures put in place must be reviewed periodically and in the event of any significant change in working conditions.

Drawing up and updating the DRPCE

Any company exposed to the risk of explosion must draw up an explosion protection document (DRPCE). The DRPCE must be incorporated into the occupational risk assessment document, be regularly updated, and contain the following information in particular:

• Explosion risk assessment;
• The nature of the measures taken or to be taken to comply with the regulations ;
• Classification of ATEX zones and description of zones to which minimum requirements apply in application of the decree of July 8, 2003;
• The methods and rules by which workplaces and equipment are designed, used and maintained to ensure the health and safety of workers;
• Where applicable, the list of work to be carried out in accordance with the employer's written instructions or subject to the issue of a permit.

Please note: the DRPCE must be drawn up before work begins and be revised whenever significant changes, extensions or transformations are made to workplaces, work equipment or work organization.

Ensure compliance of equipment and protective systems used in ATEX zones

Regulations require that all appliances , electrical and non-electrical equipment present in ATEX zones, as well as protection systems, must comply with the technical specifications defined for each zone.

These devices and protection systems are divided into two groups:

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These devices are subject to design rules and conformity assessment by the manufacturer.

Good to know: equipment complying with harmonized standards or parts of harmonized standards published in the Official Journal of the European Union (OJEU) is presumed to comply with the essential safety requirements covered by these standards or parts of standards. essential safety requirements covered by these standards or parts of standards. Particular mention should be made of the NF EN 60079 series of standards, Explosive atmospheres, Parts 0 to 31: Equipment, requirements, zoning aids and protection methods.

The employer must ensure that each piece of equipment has an EU declaration of conformity, as well as CE marking:

• The identification number of the body authorized to carry out the conformity assessment:
• The specific "Epsilon-X" explosion protection marking and the device group and category symbols;
• Where applicable, a mark indicating the specific explosive atmospheres for which the product is designed.

Some useful resources...

• ‍L'explosion d'Atex sur le lieu de travail, brochure ED 6337, INRS‍
• Fire and explosion in the workplace, brochure ED 4702, INRS‍
• Atex risk assessment grid, Tool 107, INRS

Regulatory sources

• Labor Code, articles R. 4216-31 and R. 4227-42 to R. 4227-54 (explosion prevention)
• Code de l'environnement, articles R. 557-7-1 to R. 557-7-9 (conformity of equipment and protective systems intended for use in potentially explosive atmospheres)
• Decree of July 8, 2003 on the protection of workers liable to be exposed to an explosive atmosphere.

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Photo credit: 75306586 @Aleksandr Volkov