20-point checklist for a safe system of work in confined spaces

23 August 2017

confined spaces

Anyone, in any industry, can be exposed to working in confined spaces - sometimes without even realising it. It's important to mitigate the risks associated with confined spaces, which can be fatal. Here's our 20-point checklist for producing a safe system of work in such conditions:

1. Supervision

The degree of supervision should be based on the findings of the risk assessment. In some cases an employer might simply instruct an employee how to do the work and then periodically check that all is well, for example if the work is routine, the precautions straightforward, and all the arrangements for safety can be properly controlled by the person carrying out the work. It is more likely that the risk assessment will identify a level of risk that requires the appointment of a competent person to supervise the work and who may need to remain present while the work is being undertaken.

It will be the supervisor’s role to ensure that the permit-to-work system, where applicable, operates properly, the necessary safety precautions are taken, and that anyone in the vicinity of the confined space is informed of the work being done.

2. Competence for confined space working

Workers must have adequate training and experience in the particular work involved to be competent to work safely in a confined space. Training standards must be appropriate to the task, and to the individual’s roles and responsibilities, so that work can be carried out safely. Where the risk assessment indicates that properly trained individuals can work for periods
without supervision, you should check that they are competent to follow the established safe system of work and have been provided with adequate information and instruction about the work to be done.

3. Communications

An adequate communication system must be in place and should enable communication:
(a) between those inside the confined space; (b) between those inside the confined space and those outside; and (c) to summon help in case of emergency. Whatever system is used, and it can be based on speech, tugs on a rope, the telephone, radio etc, all messages should be able to be communicated easily, rapidly and unambiguously between relevant people.
Consider whether the communication methods are appropriate for any workers wearing breathing apparatus. The communication system should also cover the need for those outside the space to raise the alarm and set in motion emergency rescue procedures.
Equipment such as telephones and radios should be specially protected so that they do not present a source of ignition where there is a risk of flammable or potentially explosive atmospheres.

4. Testing/monitoring the atmosphere

Prior to entry, the atmosphere within a confined space should be tested to check the oxygen concentration or for the presence of hazardous gas, fume or vapour. Testing should be carried out where knowledge of the confined space (e.g. from information about its previous contents or chemicals used in a previous activity in the space) indicates that the atmosphere might be contaminated or to any extent unsafe to breathe, or where any doubt exists as to the condition of the atmosphere. Testing should also be carried out if the atmosphere was known to be contaminated previously, was ventilated as a consequence, and needed to be tested to check the result.

5. Gas purging

Where the risk assessment has identified the presence or possible presence of flammable or toxic gases or vapours, there may be a need to purge the gas or vapour from the confined space. This can be done with air or an inert gas where toxic contaminants are present, but with inert gas only where there are flammable contaminants. You can only use inert gas for
purging flammable gas or vapour because any purging with air could produce a flammable mixture within the confined space. Where purging has been carried out, the atmosphere must be tested to check that purging has been effective, and that it is safe to breathe, before allowing people to enter.

6. Ventilation

Some confined spaces require mechanical ventilation to provide sufficient fresh air to replace the oxygen that is being used up by people working in the space, and to dilute and remove gas, fume or vapour produced by the work. This can be done by using a blower fan and trunking and/or an exhaust fan or ejector and trunking (provided that there is an adequate supply of fresh air to replace the used air). Fresh air should be drawn from a point where it is not contaminated either by used air or other pollutants. Never introduce additional oxygen into a confined space to ‘sweeten’ the air as this can lead to oxygen enrichment in the atmosphere that can render certain substances (e.g. grease) liable to spontaneous combustion, and will greatly increase the combustibility of other materials. Oxygen above the normal concentration in air may also have a toxic effect if inhaled.

7. Removal of residues - cleaning

Cleaning or removal of residues is often the purpose of confined space work. In some cases residues will need to be removed to allow other work to be undertaken safely. Appropriate measures should be taken where risks from the residues are identified. For example, dangerous substances (such as hazardous gas, fume or vapour) can be released when residues are disturbed or, particularly, when heat is applied to them. The measures might include the use of powered ventilation equipment, specially protected electrical equipment for use in hazardous atmospheres, respiratory protective equipment and atmospheric monitoring. The cleaning or removal process might need to be repeated to ensure that all residues have been removed, and may need to deal with residues trapped in sludge, scale or other deposits, brickwork, or behind loose linings, in liquid traps, in joints in vessels, in pipe bends, or in other places where removal is difficult.

8. Isolation from gases, liquids and flowing materials

Confined spaces should be securely isolated from ingress of substances that could pose a risk to those working within the space. An effective method is to disconnect the confined space completely from every item of plant either by removing a section of pipe or duct or by inserting blanks. If blanks are used, the spectacle type with one lens solid and the other a
ring makes checking easier. When disconnection cannot be done in this way one alternative is a suitable, reliable valve that is locked shut, providing there is no possibility of it allowing anything to pass through when locked, or of being unlocked when people are inside the confined space.

9. Isolation from mechanical and electrical equipment

Some confined spaces contain electrical and mechanical equipment with power supplied from outside the space. Unless the risk assessment specifically enables the system of work to allow power to remain on, either for the purposes of the task being undertaken or as vital services (ie lighting, vital communications, fire fighting, pumping where flooding is a risk, or cables distributing power to other areas), the power should be disconnected, separated from the equipment, and a check made to ensure isolation has been effective.

10. Selection and use of suitable equipment

Any equipment provided for use in a confined space must be suitable for the purpose. Where there is a risk of a flammable gas seeping into a confined space and which could be ignited by electrical sources (eg a portable hand lamp), specially protected electrical equipment should be used, for example a lamp certified for use in explosive atmospheres. Note that specially designed low-voltage portable lights, while offering protection against electrocution, could still present ignition sources and are not in themselves safer in flammable or potentially explosive atmospheres. All equipment should be carefully selected bearing in mind the conditions and risks where it will be used. Earthing should be considered to prevent static charge build-up. In addition to isolation, mechanical equipment may need to be secured against free rotation, as people may tread or lean on it, and risk trapping or falling.


Get your FREE copy of our Confined Spaces whitepaper


11. Personal Protective Equipment (PPE) & Respiratory Protective Equipment (RPE)

So far as reasonably practicable you should ensure that a confined space is safe to work in without the need for personal protective equipment (PPE) and respiratory protective equipment (RPE). PPE and RPE should be a last resort, except for rescue work (including the work of the emergency services), because its use can make movement more difficult, it can add to the effects of hot temperature and can be heavy. Your risk assessment may identify the need for PPE and RPE, in which case it should be suitable and should be provided and used by those entering and working in confined spaces. Such equipment is in addition to engineering controls and safe systems of work.

12. Portable gas cylinders and internal combustion engines

Never use petrol-fuelled internal combustion engines in confined spaces because of the fumes they produce and the ease with which petrol vapour ignites. Gas cylinders should not normally be used within a confined space unless special precautions are taken. Portable gas cylinders (for heat, power or light), and diesel-fuelled internal combustion engines are nearly as hazardous as petrol-fuelled engines, and are inappropriate unless exceptional precautions are taken.

13. Gas supplied by hoses and pipes

The use of pipes and hoses for conveying oxygen or flammable gases into a confined space should be controlled to minimise the risks. It is important that at the end of every working period, other than during short interruptions, the supply valves for pipes and hoses should be securely closed before the pipes and hoses are withdrawn from the confined space to a place that is well ventilated. Where pipes and hoses cannot be removed, they should be disconnected from the gas supply at a point outside the confined space and their contents safely vented.

14. Access and egress

You should provide a safe way in and out of the confined space. Wherever possible, allow quick, unobstructed and ready access. The means of escape must be suitable for use by the individual who enters the confined space so that they can quickly escape in an emergency. Suitable means to prevent access should be in place when there is no need for anybody to work in the confined space. The safe system of work should ensure that everyone has left the confined space during ‘boxing-up’ operations, particularly when the space is complicated and extensive (for example in boilers, cableways and culverts where there can be numerous entry/exit points).

15. Fire prevention

Wherever possible, flammable and combustible materials should not be stored in confined spaces that have not been specifically created or allocated for that purpose. If they accumulate as a result of work they should be removed as soon as possible and before they begin to create a risk. Where flammable materials need to be located in a confined space, the quantity of the material should be kept to a minimum. In most cases flammable materials should not be stored in confined spaces. However, there may be special cases where this is necessary, for example in tunnelling. In these cases they should be stored in suitable fire-resistant containers. If there is a risk of flammable or potentially explosive atmospheres, take actions to eliminate the risk such as removal by cleaning, effective use of thorough ventilation, and control of sources of ignition.

16. Lighting

Adequate and suitable lighting, including emergency lighting, should be provided. For example, the lighting should be specially protected if used where flammable or potentially explosive atmospheres are likely to occur. Other gases may be present that could break down thermally on the unprotected hot surfaces of a lighting system and produce other toxic products. Lighting may need to be protected against knocks (e.g. by a wire cage), and/or be waterproof. Where water is present in the space, suitable plug/socket connectors capable of withstanding wet or damp conditions should be used and protected by residual current devices (RCDs). The position of lighting may also be important, for example to give ample clearance for work or rescue to be carried out unobstructed.

17. Statis electricity

Exclude static discharges and all sources of ignition if there is a risk of a flammable or explosive atmosphere in the confined space. All conducting items, such as steel trunking and airlines, should be bonded and effectively earthed. If cleaning operations are to be carried out, assess the risks posed by the use or presence of high-resistivity materials (such as synthetic plastics) in and adjacent to the confined space.

18. Smoking

The results of the risk assessment may indicate that it is necessary to set an exclusion area for smoking to a suitable distance beyond the confined space, for example where there is a risk of explosion.

19. Emergencies & rescue

The arrangements for emergency rescue, required under regulation 5 of the Confined Spaces Regulations, must be suitable and sufficient. If necessary, equipment to enable resuscitation procedures to be carried out should be provided. The arrangements should be in place before any person enters or works in a confined space. A major cause of death and injury in confined spaces incidents is due till-conceived attempts to save others who have collapsed or ceased to respond. You should not enter a confined space without ensuring you will not also be affected.

20. Limited working time

There may be a need to limit the time period that individuals are allowed to work in a confined space, for example where RPE is used, or under extreme conditions of temperature and humidity, or if the confined space is so small that movement is severely restricted. For a large confined space and multiple entries, a logging or tally system may be necessary to check everyone in and out and to control duration of entry. There may be additional risks to consider when entry to a confined space is required. These could include the integrity of the confined space (e.g. corroded structure, cold temperatures, loss of rigidity when a tank is drained, trip hazards, noise etc). While these are not specific risks or limited to confined spaces, they
should still be considered as part of the general risk assessment and tackled as far as reasonably practicable.


Our in-depth whitepaper examines the risks associated with confined spaces and how best to mitigate them.  Download your copy today.