Guidance Note 5 – Confined spaces

This Guidance Note gives practical information about working in confined spaces.

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Sample templates have been included in Appendices 1, 2 and 3. If you wish to use these templates to construct your own documents, you must ensure that all references to Alcumus SafeContractor Accreditation have been removed and the final documents are clearly incorporated into your existing safety management system.

Working in a confined space is a hazardous operation. Several people are killed or seriously injured in confined spaces each year. Such incidents repeatedly involve more than one fatality because untrained people attempt to rescue their workmates without proper equipment and training.

What is a confined space?

A confined space is an enclosed space where there is a risk of death or serious injury from hazardous substances or dangerous conditions (e.g. lack of oxygen).

A confined space has one or more of the following characteristics:

Some confined spaces are obvious such as storage tanks, silos, enclosed drains and sewers. However, others may be less obvious, such as vats, ductwork, unventilated / poorly ventilated rooms and open-topped chambers.

Principle hazards of a confined space

Legal duties

Employers are legally required to carry out a risk assessment under the Management of Health and Safety at Work Regulations 1999. For work in confined spaces this means identifying the hazards present, assessing the risks and determining what precautions to take. The assessment will normally include consideration of:

If your risk assessment identifies serious risk of injury from working in confined spaces, the Confined Spaces Regulations 1997 apply. The key requirements of the regulations are:

Avoiding entry to a confined space

You must consider whether the work can be done in another way so that entry or work in a confined space can be avoided. Good planning and adopting a different approach can reduce the need for confined space working.

Safe systems of work

You must have a safe system of work in place for work in a confined space. The safe system of work, and any precautions identified must be developed and put into practice. Everyone involved must be properly instructed to ensure they know what to do and how to do it safely.

The results of your risk assessment will help to identify the necessary precautions to reduce the risk of injury.

Risk assessment

A suitable and sufficient risk assessment must be carried out by a competent person prior to work in a confined space. The risk assessment should question the following:

Where possible, keep hazards out of a confined space. For example, petrol or diesel engines should never be used inside the space, substances which emit solvent vapours should not be used, and burning processes should be undertaken outside of the space and the articles then lowered into place.

The work should be carried out from outside a confined space where possible. For example, cameras may be used to inspect inside confined spaces, or cleaning or sampling may be undertaken using tools from outside the space.

* See Appendix 2.

Permit to work

A permit-to-work system is a formal written system and is an extension of the safe system of work. A permit is used where there is a reasonably foreseeable risk of serious injury in entering or working in the confined space. The use of a permit system does not, by itself, make the job safe. It supports the safe system, providing a ready means of recording findings and authorisations required to proceed with entry.

A permit-to-work system may not be required where:

The decision not to adopt a permit-to-work system must only be taken by a competent person, considering the advice of specialists and the results of the risk assessment.

The permit-to-work should include the following information:

On satisfactory completion of the job, the authorising person should cancel the permit.

Re-issue of the permit

If the work has not been completed before the permit expires, a re-issue of the permit is required. The responsible person must visit the location and ensure that conditions have not substantially altered since the certificate was initially issued. If the conditions have altered the situation must be reassessed and, as necessary, further controls should be specified.

End of operations

On completion of work in the confined space, the permit must be signed-off and returned to the permit issuer, stating that the work area is safe for normal operations and that all workers are clear from the space.

The process operator should check the essential services and if agreed, the permit should be cancelled.

Operation review and revision

Following each operation, the procedures will be reviewed and revised, as necessary. Periodically, persons in charge should review the permit-to-work system to ensure that permits are being correctly completed, and that the required controls are being adopted.

* See Appendix 3.

Procedure prior to entering a confined space

If entry into a confined space is essential, a safe system of work must be adopted. The findings of the risk assessment should be used to identify the control measures.

Before any work in confined spaces starts, the following steps should be completed:

Provision of ventilation

Natural ventilation may be sufficient in certain circumstances, but most spaces will require mechanical ventilation e.g. where portable gas cylinders and diesel fuelled equipment are used inside the space.

To ensure ventilation is adequate:

Atmospheric monitoring

Before anyone enters the confined space, the atmosphere should be tested for various gases, such as:

If the atmosphere contains hazardous levels of contaminants, or is oxygen deficient, the following steps are recommended:

Safety data sheets should be kept to hand so that they are readily available to the emergency services in the event of an incident.


It is recommended that the minimum size of an opening to allow access with full rescue apparatus be 575mm diameter or minor axis. Existing plant may have smaller access points, but they should not be less than 457mm diameter round, or 457mm long and 410mm wide if oval or rectangular.

Sewers of dimensions smaller than 900mm high x 600mm wide should not be entered, and where shafts contain a ladder or step irons, 900mm clear space should be provided between the ladder/steps and back of the shaft.

Emergency arrangements

Before anyone goes into the confined space, suitable rescue (and resuscitation) arrangements must be in place.

It is essential that the method of rescue proposed does not put the rescuers health and safety at risk.

Emergency arrangements must include:

Employee training

Every worker who enters a confined space, their supervisors and attendants must be given suitable and sufficient training.

Specific training should be devised for supervisors, entrants, attendants, and rescuers. Although the training will vary with each task, in general, everyone should be trained on:

Both theoretical knowledge and practical experience are vital. Drills should ensure that the workers know how to respond if an alarm sounds, and how to use breathing apparatus correctly.

Further guidance: