The Document relating to protection against explosions (DRPCE)

Risk assessment is the first step in the prevention process. The results of this assessment must be included in the explosion protection document (DRPCE), which is included in the single occupational risk assessment document. When there is a risk of an ATEX forming, technical and organizational measures must be implemented to, as a priority, prevent the formation of an explosive atmosphere, eliminate sources of ignition, and reduce the consequences of the explosion.

The general principle of explosion risk prevention aims first to prevent an explosion from occurring and, if it does occur, to limit its effects. To this end, the employer must implement technical and organizational measures to prevent the formation of explosive atmospheres and eliminate sources of ignition. It must also ensure that the consequences of explosions are reduced. The implementation of preventive measures adapted to a given work situation requires a risk assessment step. This step is essential because it ensures the effectiveness of the measures and their sustainability. All the information from the assessment is compiled in the DRPCE, integrated into the single professional risk assessment document (DUERP).

What the DRPCE must contain

• explosion risks identified, assessed and updated

• the appropriate measures taken or to be taken to achieve the regulatory objectives and the program for their implementation

• the validation and monitoring of these measures (effectiveness, sustainability, residual risks, etc.)

• locations classified into zones (with their volumes)

• the locations to which the regulatory requirements apply

• ensuring that workplaces and equipment are designed, used and maintained with safety in mind

• the procedures to be applied and written instructions to be established before carrying out work in the areas concerned

• the content of the training of the employees concerned

How to assess the risk of explosion

Carry out product inventory

This first step consists of making an inventory of combustible products, identifying in particular:

• their nature and state of division: solid, fluid, gas, fog, powder;

• their physicochemical characteristics

  Following this inventory, it is necessary to identify:

  • the quantities used at all stages: processes, storage, handling, transfer, etc.

  • storage conditions: locations, immediate environment, temperature, etc.

Analyze the implementation processes

The normal operation of the installations must be described by collecting all the data concerning it. From this description, it is important to take into account the products used, the temperature and pressure conditions, exothermic reactions, decomposition products, cooling conditions, ventilation systems, etc.

Each installation (silo, crusher, dust collection circuit, transfer circuit, mixer, unloading system, etc.) and workstation (loading, storage, mixing, etc.) must be the subject of a study which will take into account the different operating conditions (closed systems, confined enclosures, unloading station using a dipping pipe, etc.).

Investigate potential malfunctions

The types of malfunctions that can reasonably be expected must be taken into account, such as: shutdown of the ventilation or cooling system, product leaks, particularly at the flanges and fittings, foreseeable breakdowns, product supply interruptions, etc.

Feedback from the company or industry can help to highlight malfunctions such as:

• instructions that are not applicable (especially in the event of an anomaly) or not actually applied,

• incidents during operation or during shutdown or restart phases,

• a theoretical production process that cannot be respected given the demands and constraints (travel, additional tasks that take longer than the main task, etc.).

Classify hazardous locations (zoning)

Locations where an ATEX may be present are classified as risk zones depending on the nature of the combustible product, the frequency and duration of the presence of the explosive atmosphere in question.

Atmosphere type	Area	Definition	Typical example
Flammable gases, vapors or mists	Zone 0	Explosive atmosphere present permanently or for long periods.	Interior of a tank containing a flammable solvent.
	Zone 1	Explosive atmosphere that may occasionally occur during normal operation.	Immediate proximity to a fuel filler valve.
	Zone 2	Explosive atmosphere unlikely to form, and if it does form, it is only briefly.	Areas near controlled accidental leaks.
Combustible dust	Zone 20	Explosive atmosphere present permanently or frequently in the form of a cloud of combustible dust.	Interior of a silo or dust filter.
	Zone 21	Explosive atmosphere may occasionally occur during normal operation.	Environment close to a flour conveyor.
	Zone 22	Explosive atmosphere unlikely to form, and if it does form, it is only briefly.	Dust deposits around equipment in a factory.

Identify sources of ignition

There are many sources of ignition. They are all detailed in the NF EN 1127-1 standard.

Assessing the severity of an explosion

The concept of severity must be assessed based in particular on the presence of personnel, the volume of the ATEX zone and the explosion protection of the installations. It will also be relevant to take into account the risk of propagation of the explosion, in storage for example, leading to a risk of secondary explosion or propagation of a fire. Following this assessment, prevention and protection measures must be put in place.

Research into prevention and protection measures

The search for prevention and protection measures focuses, as a priority, on preventing the formation of an explosive atmosphere, then on avoiding its ignition and finally on limiting the effects of an explosion by putting in place protection systems, in order to protect the health and safety of employees.

The implementation of preventive, technical and organizational measures, subject to their sustainability, is recorded in an action plan and will make it possible to define potentially less restrictive zoning.

It is recommended to involve all internal and even external skills (ATEX reference persons certified by the CNPP or INERIS) in the drafting of this document . The DRPCE is finalized under the responsibility of the employer and submitted for opinion to the staff representative bodies (CSE, etc.).

Source :

INRS