What is a Confined Space?

A confined space is any area that “by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk.”

This definition comes from the Confined Space Regulations 1997 (the Regulations). In practice, this means any enclosed (or partly enclosed) area that poses a significant risk of death or injury counts as a confined space. Examples listed in the Regulations include:

• Chambers
• Tanks
• Vats
• Silos
• Pits
• Pipes
• Sewers
• Flues

This list isn’t exhaustive. A confined space is defined by the risks it presents, not by its physical features. It’s important to define them this way because confined spaces aren’t always obvious. For instance, some are a temporary result of construction work.

Other spaces don’t fit the casual definition of confined or may appear safe at first. You might not consider cellars a confined space, for example. Open-topped chambers might also be discounted because there’s no overhead barrier trapping workers inside. But these spaces can present specified risks to workers because they’re partly enclosed.

A thorough risk assessment is necessary to determine whether an area is a confined space. If it shows one or more specified risks are present, you must ensure any work carried out in it complies with the Regulations.

The “specified risks” are outlined in the Confined Space Regulations 1997. These risks come directly from the enclosed or partially enclosed nature of the space. They are:

• Fire and Explosion: Flammable gases or vapours can accumulate and lead to explosions or fires.
• Increase in Body Temperature: Workers can lose consciousness due to dangerously high temperatures.
• Asphyxiation: Loss of consciousness can occur from a lack of oxygen caused by:
  • Gas
  • Fumes
  • Vapours
  • Limited oxygen supply
• Drowning: Water or other liquids can cause drowning if they suddenly flood the area.
• Free-Flowing Solids: Substances like grain or sand can shift suddenly and bury workers, causing asphyxiation or cutting them off from areas with adequate oxygen supply.

If your assessment finds one or more of these risks, you must comply with the Regulations.

Your legal duties start with a risk assessment of the work you need to carry out. This is a requirement under the Management of Health and Safety at Work Regulations 1999. Your assessment must consider the:

• Work being done
• Working environment
• Working materials and tools
• Suitability of workers
• Emergency arrangements

Work must comply with the Confined Spaces Regulations 1997 if the assessment identifies a specified risk.  Under the Regulations, you must:

• Avoid the work if possible: Whenever practical, tasks should be completed from outside the enclosed space.
• Follow a safe system of work: If entry is unavoidable, create a safe system based on the risk assessment’s findings.
• Make emergency arrangements: Develop a comprehensive rescue plan and ensure all necessary equipment and personnel are ready before work begins.

Other regulations may apply depending on the work carried out.

• Provision and Use of Work Equipment Regulations 1998 (PUWER): Maintenance work involving large plant and machinery may require personnel to work within the equipment itself, potentially creating a confined space. In these situations, you must comply with PUWER to ensure all maintenance work is safe.
• Personal Protective Equipment at Work Regulations 2022: Working in a confined space often requires personal protective equipment (PPE) like helmets, gloves and breathing apparatus. Under these regulations, you must supply suitable PPE and ensure it’s used correctly.

Safety measures depend on the nature of the work and the environment in which it is performed, so always refer to your risk assessment.

With this said, some measures apply to all forms of work in confined spaces. These are:

• Appoint a Supervisor: Competent supervisors need to oversee all work and check safety precautions at every stage.
• Select Suitable Workers: Workers must be competent, with the necessary knowledge, experience and training to carry out the task safely. You should also consider if they’re physically suited to the job. For example, are they able to comfortably enter and navigate the space?
• Prepare Emergency Arrangements: Develop a comprehensive emergency plan, including communication methods, entry to confined spaces for rescuers and necessary equipment. Run regular drills to familiarise all participants with their roles and identify areas for improvement.
• Have First-Aiders On-Site: Ensure trained first-aid personnel are available to respond promptly in case of an incident.

For further advice on individual safety measures, you can look at the Health and Safety Executive’s website.

• Definition and Risk Assessment: A confined space is defined by the presence of specified risks, such as fire, explosion, drowning or asphyxiation. Conduct a thorough risk assessment to identify these risks and determine the necessary safety measures.
• Legal Responsibilities: Employers are legally required to assess the work environment, the tasks being done and the suitability of workers. If a specified risk is found, the work must comply with the Confined Spaces Regulations 1997.
• Avoid Work in Confined Spaces Whenever Possible: It’s always safest to avoid entry to confined spaces. Consider alternative methods to complete the work from outside the space first. If this is impossible, follow a safe system of work and have a clear emergency plan.
• Safety Measures: General safety measures include appointing a supervisor, ensuring workers are suitable and preparing and practising emergency plans.
• Training: Proper training ensures that all team members understand the hazards, know how to follow safe systems of work and can act appropriately in emergencies.

Training is essential for working in confined spaces. Everyone involved needs to be trained and given clear instructions so they understand their tasks and can perform them safely.

Our online Confined Space Training course makes workers aware of the hazards they may face and relevant control measures. It’s not enough to qualify someone to work in confined spaces on its own, but it covers the fundamentals of safe working and emergency procedures.