Working Safely in Confined Spaces: Principles Under UK Law and ACOP L101
- kathybarrett2020
- Oct 27
- 4 min read
Working in confined spaces presents unique and serious hazards. Whether it's a tank, silo, sewer, or poorly ventilated basement, these environments can pose significant risks — including suffocation, fire, explosion, and loss of consciousness. In the UK, safety in such environments is governed by The Confined Spaces Regulations 1997, supported by the Approved Code of Practice (ACOP) L101. These regulations outline legal duties and practical guidance for employers, self-employed individuals, and employees.
In this blog, we’ll explore the key principles for working safely in confined spaces according to these regulations.
What Is a Confined Space?
Under the Confined Spaces Regulations 1997, a confined space is defined as:
"Any place, including any chamber, tank, vat, silo, pit, trench, pipe, sewer, flue or well, which, by virtue of its enclosed nature, creates a reasonably foreseeable risk."
Such risks may include:
Fire or explosion
Loss of consciousness due to toxic gases
Oxygen deficiency or enrichment
Drowning from liquids
Asphyxiation from free-flowing solids
Importantly, a space does not need to be small to be considered confined — it simply needs to have limited access or egress and a foreseeable risk to health or life.
Key Principles for Safe Working in Confined Spaces
1. Avoid Entry Wherever Possible
The first principle under Regulation 4 is clear:
“No person at work shall enter a confined space to carry out work for any purpose unless it is not reasonably practicable to achieve that purpose without such entry.”
Employers must assess whether the work can be done remotely, using tools or equipment, or by altering the process. If entry is required then key principle number 2 is essential.
2. Undertake a Suitable and Sufficient Risk Assessment
Before any work begins, a thorough risk assessment must be completed. This includes identifying:
The nature of the hazards (toxic gases, flammable vapours, oxygen levels)
The type and duration of the work
Methods of communication
Rescue procedures
This is a key requirement under the Management of Health and Safety at Work Regulations 1999, and ACOP L101 provides detailed examples of how to conduct such assessments. Or you can speak to a specialist in this area, who is able to consult with you on the work and write the assessments for you.
3. Implement Safe Systems of Work
If entry is unavoidable, employers must establish a safe system of work, tailored to the identified risks. This typically includes:
Isolation of potentially hazardous substances (e.g. locking off valves, blanking pipes)
Ventilation systems to remove harmful fumes or supply breathable air
Permit-to-work systems to control entry and monitor the process
Use of appropriate personal protective equipment (PPE) such as breathing apparatus
Regular monitoring of atmospheric conditions inside the space
ACOP L101 provides specific guidance on each of these steps, ensuring best practices are followed. Any consultant or third party rescue team should follow these best practices and provide you with written documentation on the agreed safe systems of work.
4. Ensure Adequate Training and Supervision
Only those with proper training, competency, and understanding of the risks should work in or around confined spaces. This includes both workers and supervisors.
Training should cover:
Hazards specific to confined spaces
Use of gas detectors, PPE, and emergency equipment
Safe entry and exit procedures
Emergency rescue techniques
Ongoing supervision ensures procedures are followed, and deviations can be addressed immediately. You will be able to access this training via a third party to upskill your team, or bring in trained professionals to deliver the supervision for you.
5. Establish and Rehearse Emergency Arrangements
According to Regulation 5, suitable and sufficient emergency arrangements must be in place. This includes:
A clear and practiced rescue plan
Provision of appropriate rescue equipment
Availability of trained rescue personnel
Communication systems that function inside and outside the confined space
Importantly, relying solely on emergency services is not acceptable. Employers must make specific provisions and ensure they are effective through regular drills and reviews. Any consultant or third party provider will provide you with all of the above, including running you through real life potential scenarios so you and your team are prepared for every eventuality.
All rescue plans must be:
Suitable
Sufficient
Immediate
Legal Responsibilities
The regulations place duties on:
Employers and self-employed persons to protect themselves and others
Employees to cooperate with procedures and use equipment properly
Contractors and third parties to coordinate efforts and share relevant information
Failure to comply can result in prosecution, fines, or even imprisonment — especially in the case of serious injury or fatality.
Final Thoughts
Working in confined spaces is inherently risky — but those risks can be controlled through proper planning, training, and execution. The Confined Spaces Regulations 1997 and ACOP L101 provide a strong legal and practical framework to ensure that employers take all reasonable steps to protect workers.
By following these principles:
Avoid entry if possible
Assess the risks thoroughly
Create a robust safe system of work
Train and supervise all personnel
Prepare for emergencies
...you can ensure a safer working environment for everyone involved. If you would like to understand more detail on working safely in confined spaces, or are looking for a confined space rescue team that meets all the above criteria, please call ResQsupport on 0800 1125 999 or email us on contact@resqsupport.co.uk - we are happy to help.
Further Resources
For advice tailored to your business or industry, consult with a competent health and safety professional like ResQsupport.