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Everything you need to know about confined spaces

Confined spaces are a feature of many industrial sectors, and thousands of employees are concerned. These spaces pose numerous risks due to oxygen-depleted, toxic or explosive atmospheres, in addition to the risk of falling or drowning.

Before any work is carried out, certain precautions have to be taken and staff need to be trained in order to limit the risk of accidents.

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Confined space

What is a confined space?

A confined space is defined as an area that is partially or completely closed and has the following characteristics:

  •     Not designed to be occupied by people on the inside.
  •     Operations in confined spaces are therefore considered to be exceptional, whether they are performed at the construction stage, for servicing (cleaning, primarily) or maintenance (periodic inspections, repairs) purposes.
  •     Access is restricted both inside and outside.
  •     When entering such spaces, operators may be exposed to a significant number of risks, that need to be controlled (lack of natural ventilation, type of work to be carried out)

Examples of confined spaces include:
Wells and pits, pipes, sewers, manifolds which can be entered, wet wells, degritting stations, chlorination and ozonation stations in water treatment plants, long, narrow galleries, cisterns, reservoirs, tanks, sludge treatment and storage facilities, storage rooms containing chemicals, silos, crawl spaces, cellars

Who enters confined spaces?

  •     Employer or owner of the space
  •     Upkeep and maintenance services
  •     Specialist service providers
  •     Rescue teams
  •     Emergency services

Why enter a confined space?

  •     To carry out an inspection or surveillance
  •     For cleaning purposes
  •     To carry out repairs and servicing
  •     To carry out building work
  •     For rescue operations

What is the regulatory framework for confined spaces?

 INRS has defined protection methods for work carried out in these environments, which are laid down in:

  •     RECOMMENDATION: R447 – for the prevention of accidents when working in confined spaces
  •     GUIDE: ED6184 – Confined spaces
  •     TRAINING: CATEC (R472 and ED6026 from INRS) – training for companies which may be required to perform work on drinking water and wastewater networks

What are the risks related to confined spaces?

Confined spaces are dangerous because they contain an atmosphere that is not easily renewed. The hazards related to confined spaces need to be taken into consideration before entering the space or rescuing a person. They are split into three categories:

  •     Physical hazards (risk of falling, mechanical, electrical and thermal hazards)
  •     Hazards related to the atmosphere (risk of asphyxiation, intoxication, fire-explosion)
  •     Hazards related to the configuration (access risks)

La majorité des accidents souvent graves voire mortels qui surviennent lors d’interventions en espaces confinés est liée à une atmosphère déficiente en oxygène, à la présence de gaz ou de vapeurs toxiques.

Most serious or even fatal accidents that occur during work performed in confined spaces are related to an oxygen-depleted atmosphere or the presence of toxic gases or vapours.

What are the prevention measures?

Identifying and preventing risks requires prior analysis of the situation, sound knowledge of the processes (materials used, chemical and biological reactions, etc.), and a reconnaissance inspection of the premises.

Once this groundwork has been carried out, plans and permits need to be arranged. The following aspects need to be addressed:

  •     Appoint a person responsible
  •     Draw up a prevention plan and specific work procedures
  •     Acquire the permits for entering confined spaces
  •     Train the people concerned
  •     Inform people about the measures to be taken in the event of an incident or accident.

The last point concerns the condition of all equipment items, which must be inspected and checked:

For access
Material (davit arms and tripods), harnesses, winches and rescue equipment, gas detection, etc.

For work inside
Emergency escape breathing devices, respiratory protective equipment and welding equipment, breathing apparatus, gas detection, helmets, ear protection and communication accessories, safety glasses, protective gear, fall protection for tools, fans, etc.

For rescue
Breathing apparatus, davit arms and tripods, harnesses, winches and rescue equipment, etc.


It is recommended to avoid working from the outside, to put in place collective fall protection equipment and measures to control the atmosphere and prevent drowning and electrocution, and, lastly, to provide Personal Protective Equipment (PPE designed for falls, gas risks, etc.)