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Safety - Confined Space Working

Updated on June 1, 2009

This lens is aimed at employers and the self-employed who carry out work in confined spaces, and forms part of my commitment to make simple and practical guidance available for everyone. It will help them take the necessary action to meet the requirements of Confined Spaces Regulations. It will also be a useful source of information to anyone involved in carrying out work in confined spaces.

About the Author

What makes me qualified to tell you about Safety at Work?

I have been a Chartered Engineer for about 14 years and have over 20 years experience of working in a variety of industrial environments that have all included hazardous working. These include Petrochem, Metal Manufacturing, Power Generation and Construction.

In that time I have promoted safe working to everybody.

For a number of years I was employed by a large American Corporation and was deemed to be the local Fall Prevention and Protection expert and introduced many new systems and methods of work.

I am now in a position where I would like to share some of the knowledge I have gained over the years.

Confined Spaces Can Be Deadly

On average, work in confined spaces kills 15 people every year in the UK across a wide range of industries, from those involving complex plant through to simple storage vessels. In addition, a number of people are seriously injured. Those killed include not only people working in the confined space but those who try to rescue them without proper training and equipment

What is a Confined Space?

It can be any space of an enclosed nature where there is a risk of death or serious injury from hazardous substances or dangerous conditions (eg lack of oxygen).

Some confined spaces are fairly easy to identify, eg enclosures with limited openings:

  • storage tanks.

  • silos.

  • reaction vessels.

  • enclosed drains.

  • sewers.

Others may be less obvious, but can be equally dangerous, for example:

  • open-topped chambers.

  • vats.

  • combustion chambers in furnaces etc.

  • ductwork.

  • unventilated or poorly ventilated rooms.

It is not possible to provide a comprehensive list of confined spaces. Some places may become confined spaces when work is carried out, or during their construction, fabrication or subsequent modification.

What are the Dangers from Confined Spaces?

Dangers can arise in confined spaces because of:

A lack of oxygen.

This can occur:

  • where there is a reaction between some soils and the oxygen in the atmosphere.

  • following the reaction of groundwater on chalk and limestone which can produce carbon dioxide and displace normal air.

  • in ships' holds, freight containers, lorries etc as a result of the cargo reacting with oxygen inside the space.

  • inside steel tanks and vessels when rust forms.

  • through the use of portable generating equipment or similar. It is particularly important to consider exhaust fumes from this type of equipment whether it is inside the confined space or not.

Poisonous gas, fumes or vapour.

These can:

  • build-up in sewers and manholes and in pits connected to the system.

  • enter tanks or vessels from connecting pipes.

  • leak into trenches and pits in contaminated land, such as old refuse tips and old gas works.

Liquids and solids.

This is hazardous when:

  • liquids or solids which can suddenly fill the space,

  • gases could be released if liquids or solids are disturbed.

  • free flowing solids such as grain in silos causing blockages collapses unexpectedly.

Fire and explosions. (eg from flammable vapours, excess oxygen etc).

Conditions to be particularly aware of include:

  • residues left in tanks, vessels etc, or remaining on internal surfaces which can give off gas, fume or vapour.

  • dust present in high concentrations, eg in flour silos which when disturbed could create a dust cloud.

Hot conditions.

You should be particularly cautious when conditions exist that could lead to a dangerous increase in body temperature.

Changing conditions.

Some of the above conditions may already be present in the confined space. However, some may arise through the work being carried out, or because of ineffective isolation of plant nearby, eg leakage from a pipe connected to the confined space. Also the enclosured working space may increase other dangers arising through the work being carried out, for example:

  • machinery being used may require special precautions, such as provision of dust extraction for a portable grinder, or special precautions against electric shock.

  • gas, fume or vapour can arise from welding, or by use of volatile and often flammable solvents, adhesives etc.


If access to the space is through a restricted entrance, such as a manhole, escape or rescue in an emergency will be more difficult (see Emergency procedures). This should be considered when planning work.

What does the Law Say?

You must carry out a suitable and sufficient assessment of the risks for all work activities for the purpose of deciding what measures are necessary for safety (The Management of Health and Safety at Work Regulations 1992, regulation 3). For work in confined spaces this means identifying the hazards present, assessing the risks and determining what precautions to take.

In most cases the assessment will include consideration of:

  • the task.

  • the working environment.

  • working materials and tools.

  • the suitability of those carrying out the task.

  • arrangements for emergency rescue.

You may need to appoint competent people to help manage the risks and ensure that employees are adequately trained and instructed (The Management of Health and Safety at Work Regulations 1992, regulation 6). Of course, you might be the best person to do this, however, you may also need to train someone else or engage the services of a competent person for additional help.

If your assessment identifies risks of serious injury from work in confined spaces, such as the dangers highlighted above, the Confined Spaces Regulations 1997 apply. These regulations contain the following key duties:

  • avoid entry to confined spaces, eg by doing the work from outside.

  • if entry to a confined space is unavoidable, follow a safe system of work.

  • put in place adequate emergency arrangements before the work starts.

These duties, and what you need to do, are further described in this lens.

Health and Safety Books

If you need to know more, these books are certainly worth checking out.

Avoid Entering Confined Spaces

The safest consideration is to eliminate working in confined spaces. You need to check if the work can be done another way so that entry or work in confined spaces is avoided.

Better work-planning or a different approach can reduce the need for confined space working. Ask yourself if the intended work is really necessary, or could you:

  • modify the confined space itself so that entry is not necessary.

  • have the work done from outside, for example:

    • blockages can be cleared in silos by use of remotely operated rotating flail devices, vibrators or air purgers.

    • inspection, sampling and cleaning operations can often be done from outside the space using appropriate equipment and tools.

    • remote cameras can be used for internal inspection of vessels.
  • modify the confined space so that it is no longer a confined space, for example:

    • remove enclosure walls to open up the space.

    • increase natural ventilation to reduce the risk of dangerous atmospheres.

    • improve access to the workplace.

Safe Systems Of Work

If you cannot avoid entry into a confined space, it is essential that you have a safe system for working inside the space.

Use the results of your risk assessment to help identify the necessary precautions to reduce the risk of injury. These will depend on the nature of the confined space, the associated risk and the work involved.

Make sure that the safe system of work, including the precautions identified, is developed and put into practice. Everyone involved will need to be properly trained and instructed to make sure they know what to do and how to do it safely.

The following checklist is not intended to be exhaustive but includes many of the essential elements to help prepare a safe system of work.

1. Supervisor Appointed?.

Supervisors should be given responsibility to ensure that the necessary precautions are taken, to check safety at each stage and may need to remain present while work is underway.

A supervisor should be competent and experienced in the type of work to be done. Training requirements should be considered specifically for this individual, does he/she need any additional training over and above the rest of the working party. A supervisor should have the confidence and awareness to instruct and direct others to ensure they follow the safe system of work.

Supervisors should be named on documentation relating to the work, for example, a method statement.

2. Suitable Persons Employed?

Are the persons employed to do the work competent?

Whether you are using your own personnel or are bringing in a contractor to do the work you need to ask this question. Do they have sufficient experience of the type of work to be carried out, and what training have they received?

Do not accept peoples word, ask for evidence. If they claim to have been trained, check training records, check certificates, importantly check to see if the training is relevant and recent.

Where risk assessment highlights exceptional constraints as a result of the physical layout, are individuals of suitable build?

The competent person may need to consider other factors, eg concerning claustrophobia or fitness to wear breathing apparatus, and medical advice on an individual's suitability may be needed.

3. Isolation Requirements?

What equipment or machinery could affect the confined space?

Mechanical and electrical isolation of equipment is essential if it could otherwise operate, or be operated, inadvertently. If gas, fume or vapour could enter the confined space, physical isolation of pipework,ducting etc needs to be made. In all cases a check should be made to ensure isolation is effective. Ideally you should have an established lock out procedure to follow.

4. Pre-entry Work Required?

Is there any work required before entry will be permitted?

Often work is required to be done to prepare an area for other work to be done. Your risk assessment should highlight any hazards that need to be addressed before an entry into a confined space is permitted. This could include cleaning work, purging or ventilation. It could include removal of other equipment or installation of equipment for example staging or work platforms. It may be necessary to ensure fumes do not develop from residues etc while the work is being done. As almost every confined space is different, only your risk assessment will highlight these requirements.

5. Access to the Confined Space?

Check the size of the entrance, is it big enough?

Is it big enough to allow workers wearing all the necessary equipment to climb in and out easily, and provide ready access and egress in an emergency?

For example, the size of the opening may mean choosing air-line breathing apparatus in place of self-contained equipment which is more bulky and therefore likely to restrict ready passage.

6. Adequate Ventilation?

Is there sufficient free air to support your workers?

It is essential that ventilation is adequate. The number of workers in the confined space and the nature of the work must be considered. If possible there should be more than one opening to allow a flow of air through the space. You may be able to increase the number of openings and therefore improve ventilation.

Mechanical ventilation may be necessary to ensure an adequate supply of fresh air. This is essential where portable gas cylinders and diesel-fueled equipment are used inside the space because of the dangers from build-up of engine exhaust. Ideally this type of equipment should be positioned outside the confined space well away from the opening.

Remember there is no such thing as too much ventilation, providing of course you don't create further hazards by turning your confined space in to a wind tunnel.

Warning: carbon monoxide in the exhaust from petrol-fueled engines is so dangerous that use of such equipment in confined spaces should never be allowed.

7. Air Quality?

Test the air for quality.

Testing of the atmosphere within a confined space is an essential part of the entry procedure that should not be missed. It is necessary to check that the air is free from both toxic and flammable vapours and that it is fit to breathe. Testing should be carried out by a competent person using a suitable gas detector which is correctly calibrated. Where the risk assessment indicates that conditions may change, or as a further precaution, continuous monitoring of the air may be necessary.

A gas monitor should be available to monitor air quality for the duration of the work. This can be a single unit for small confined spaces where the work area is small and concentrated, or preferably workers should be issued individual gas monitors to give them individual protection.

8. Is Equipment Suitable?

Are special tools and lighting required?

Non-sparking tools and specially protected lighting are essential where flammable or potentially explosive atmospheres are likely. In certain confined spaces (eg inside metal tanks) suitable precautions to prevent electric shock include use of extra low voltage equipment (typically less than 25 V) and, where necessary, residual current devices.

Any other equipment being used should be assess for suitability to use in the confined space. Nothing should be assumed to be ok without an assessment of some sort. Consider the hazards that the tool might present in a confined space, these could be different and much more significant then when they are used in a workshop environment, For example, power tools, especially grinders, generate huge amounts of noise which will create additional hazards when used in a confined space. In this example, as well as the hazard to hearing, communications have to be considered.

9. Is Breathing Apparatus Required?

Provision of breathing apparatus must be carefully controlled.

Control of the use of breathing apparatus, whether self contained or by airline, is essential if the air inside the space cannot be made fit to breathe because of gas, fume or vapour present, or lack of oxygen. Never try to 'sweeten' the air in a confined space with oxygen as this can greatly increase the risk of a fire or explosion.

Individuals required to use breathing apparatus must be fully trained in its use. A control program must be developed to log personnel using breathing apparatus. Special consideration must be given to the duration that an individual is allowed to work whilst wearing breathing apparatus and the additional rest periods that the individual will need.

If breathing apparatus is to be used, a rescue team should be on standby to effect a breathing apparatus assisted rescue in the event of an emergency.

Use of breathing apparatus is a specialized function and should only be attempted by trained professionals, if you have any doubts about your ability you need to consult an expert.

10. Emergency Arrangements in Place?

Plan for an emergency!

Plan for an emergency and be prepared. No matter how much planning and risk assessment is done, things can still go wrong very quickly when working in a confined space. The additional hazards present mean that you do not have any time to think if things do go wrong.

You might ask "What can go wrong?", especially if you have planned everything and implemented all the control measures you can think of. Unfortunately, it is impossible to cover every eventuality and the nature of the work means that there will always be some risk associated with the work.

Rather than be sorry, plan for things to go wrong.

By doing this you will be ready. Have your emergency procedures in place, practice your drills wherever you can. Make sure that other people who can help are aware that the need may arise and that they now what to do if called upon.

Make sure that you have the necessary equipment available and readily

accessible. How will you get that large worker up from the hole in ground? How will you get to somebody in a dark tunnel if all the power is lost? Ask every question you can reasonably expect to have to answer if things go wrong. As much time, if not more needs to be put in to emergency planning as the actual work itself. Document all you procedures and review them regularly.

11. Rescue Harnesses Available?

Do you need rescue harnesses?

Many workplaces specify that a rescue harness be worn for all confined space work. Harnesses are usually associated with working at height, but a full body harness worn in a confined space can be a life saver.

If a worker collapses and is unable to assist himself, the harness gives rescuers something to grab hold of. Try pulling somebody along a tunnel if they are wearing plastic overalls!

If a worker has to be lifted out of a confined space, it is a reasonably straight forward task if that worker is wearing a harness. The 'D' ring on the back of the harness can be used to attach to a tripod and winch and the worker simple lifted.

In confined spaces that involve working on tunnels or large ducting, lifelines attached to harnesses should run back to a point outside the confined space. in the event of an emergency the worker can then be traced quite easily without having to go searching.

12. Rescue Equipment Available? - Get it ready before you need it.

Don't start confined space entry work without having the correct equipment. It is essential that you have the correct equipment for rescue as well as for the entry itself. If you wait until there is an emergency it will be too late. Do not make this classic mistake.

The rescue equipment required will depend on the circumstances. You should assess what might be needed, for example, a stretcher board, a tripod and winch, breathing apparatus, or ropes are all typical of the type of equipment needed.

13. What Communications?

What are the means of communicating?

An adequate communications system is needed to enable communication between people inside and outside the confined space and to summon help in an emergency. The equipment used needs to be suitable for the environment.

Is direct verbal communication sufficient? Do you need two way radios?

Again, your risk assessment should identify any issues that have to be resoilved. If using two way radios, do they need to have a dedicated channel, or will radio silence be required of other users.

Are emergency communication routes established and personnel in place to receive communications when needed? It is important that communication requirements are established and detailed within the supporting documentation for the work.

14. Emergency Alarms Ready?

Check how the alarm will be raised.

In the event of something going wrong and an emergency situation developing, it is important that individuals know how to raise the alarm. It is often necessary to station someone outside to keep watch and to communicate with anyone inside, and then raise the alarm quickly in an emergency. Alternatively the alarm may be raised over the radio communication channels. Whichever means you have in place to raise the alarm it is critical that everybody knows about them and the actions required if the alarm is raised.

If an alarm is raised who will take charge of the rescue procedures?

15. Is a 'Permit-To-Work' Necessary?

Get all permits in place before starting work.

A good permit-to-work ensures a formal check is undertaken to ensure all the elements of a safe system of work are in place before people are allowed to enter or work in the confined space. It is also a means of communication between site management, supervisors, and those carrying out the hazardous work. Essential features of a permit-to-work are:

  • clear identification of who may authorise particular jobs (and any limits to their authority) and who is responsible for specifying the necessary precautions (eg isolation, air testing, emergency arrangements etc).

  • provision for ensuring that contractors engaged to carry out work are included.

  • training and instruction in the issue of permits.

  • monitoring and auditing to ensure that the system works as intended.

Emergency Procedures

When things go wrong, people may be exposed to serious and immediate danger. Effective arrangements for raising the alarm and carrying out rescue operations in an emergency are essential.

Contingency plans will depend on the nature of the confined space, the risks identified and consequently the likely nature of an emergency rescue.

Emergency arrangements will depend on the risks. You should consider:

  • Communications

    How can an emergency be communicated from inside the confined space to people outside so that rescue procedures can start? Don't forget night and shift work, weekends and times when the premises are closed, eg holidays. Also, consider what might happen and how the alarm can be raised.

  • Rescue and resuscitation equipment

    Provision of suitable rescue and resuscitation equipment will depend on the likely emergencies identified. Where such equipment is provided for use by rescuers, training in correct operation is essential.

  • Capabilities of rescuers

    There need to be properly trained people, sufficiently fit to carry out their task, ready at hand, and capable of using any equipment provided for rescue, eg breathing apparatus, lifelines and fire-fighting equipment. Rescuers also need to be protected against the cause of the emergency.

  • Shut down

    It may be necessary to shut down adjacent plant or equipment before attempting emergency rescue.

  • First-aid procedures

    Trained first aiders need to be available to make proper use of any necessary first-aid equipment provided.

  • Local emergency services

    How are the local emergency services (eg, fire brigade) made aware of an incident? What information about the particular dangers in the confined space is given to them on their arrival? Do your local emergency services know your site? Why not invite them for a familiarization tour?

Relevant Law

Check your locally to ensure compliance.

The law can be a minefield for those who are not aware. Here I have listed some of the relevant regulations that are applicable and that should be considered before starting any work. I can not list all elements of law for all locations so it is essential that you check locally that you are compliant with all local requirements.

Within the UK much of this is now applicable across Europe.

  • The Confined Spaces Regulations 1997.

  • The Management of Health and Safety at Work Regulations 1992.

  • The Control of Substances Hazardous to Health Regulations 1994.

  • The Personal Protective Equipment at Work Regulations 1992.

  • The Provision and Use of Work Equipment Regulations 1992.

  • Electricity at Work Regulations 1989.

  • Workplace (Health, Safety and Welfare) Regulations 1992.

Some of the above law is relevant because of the nature of the work to be carried out inside a confined space, eg where there are risks from machinery, electricity or from hazardous substances.


The information in this lens is provided for information only and does not intend to replace any training that a user must receive. The author can accept no responsibility of any kind for any accident, injury, damage or loss resulting from a person or persons using this information.

This information must not be used to replace local standards, procedures and training.

Every job must be fully assessed for risk and method before any works are performed.

If you feel you would like to add anything, this is your opportunity. Whether it is a cautionary tale, a bit of advice, or just your own comments, feel free to add for all to see.

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    • Bakersgas profile image


      6 years ago

      Great lens, working in confined spaces can be especially dangerous for welders. Thanks for the helpful information.


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