Updated: August, 2014

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 confined spaces 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 (for instance, a lack of oxygen).

Some confined spaces are fairly easy to identify, e.g. 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 or sheds

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 of 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 action of groundwater on chalk and limestone which can produce carbon dioxide and displace normal air.
     • inside steel tanks and vessels when rust forms
     • 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 which can suddenly fill the space, or release gases into it, when disturbed. Free flowing solids such as grain can also partially solidify or 'bridge' in silos causing blockages which can collapse unexpectedly.
     • Fire and explosions (e.g. from flammable vapours, excess oxygen, etc.).
     • Residues left in tanks, vessels, etc., or remaining on internal surfaces which can give off gas, fume or vapour.
     • Dust may be present in high concentrations, e.g. in flour silos.
     • Hot conditions leading to a dangerous increase in body temperature.
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, e.g. leakage from a pipe connected to the confined space.

The enclosure and 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.

What the Law Says
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 1999). 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

The HSE's free leaflet '5 Steps to Risk Assessment' will help guide you through the risk assessment process further.

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 1999).

f 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, e.g. 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.

Areas to Include for Consideration
     • Avoid entering confined spaces
     • Development of a safe system of work
     • Appointment of a supervisor
     • Are persons suitable for the work?
     • Isolation of power sources
     • Cleaning before entry
     • Check the size of the entrance - access and egress
     • Provision of ventilation
     • Testing the air quality
     • Provision of special tools and lighting
     • Provision of escape breathing apparatus
     • Preparation of emergency arrangements
     • Provision of rescue harnesses
     • Two-way communications
     • Check how the alarm is raised
     • Is a 'permit-to-work' necessary?
     • Emergency procedures
     • Rescue and resuscitation equipment
     • Capabilities and training of rescuers
     • Shut down of adjacent plant before attempting emergency rescue
     • First-aid procedures
     • Local emergency services contact and access

Hazards to Identify in Developing a Safe System of Work / Risk Assessment
     • Explosive gases/vapours
     • Toxic gases/vapours
     • Oxygen content (deficiency / enrichment)
     • Explosive gases/vapours
     • Fumes, dusts, mists, fogs
     • Smoke
     • Biological agents
Safety Hazards:
     • Entry/exit (access/egress)
     • Ventilation systems
     • Machinery
     • Piping/Distribution systems
     • Residual chemicals/materials
     • Electrical
     • Visibility
     • Physical obstacles
     • Walking/working surfaces
     • Temperature extremes
     • Humidity
     • Noise
     • Vibration
     • Radiation
     • Hazardous animals
Work to be performed: Hot work / cold work
Human Factors:
     • Phobias
     • Mental and physical condition of workers

by Dennis Mac (IOSH accredited Unite Safety Rep, retired)
The Confined Spaces Regulations 1997 - Statutory Instrument 1997 No. 1713;
"Safe Work in Confined Spaces", INDG 258, published by the Health & Safety Executive;
"Safe work in confined spaces - Approved Code of Practice, Regulations and Guidance", HSE Books,
ISBN 9780717662333

Statute Link: 
The Confined Spaces Regulations 1997
These regulations contain the following key duties:
     • avoid entry to confined spaces, e.g. by doing the work from the outside;
     • if entry to a confined space is unavoidable, follow a safe system of work; and
     • put in place adequate emergency arrangements before the work begins

Confined Spaces at Work - HSE
Confined Spaces - Toolboxtopics.com
Confined Spaces - The True Dangers of Confined Spaces - Toolboxtopics.com
Confined Spaces - Working in Confined Spaces - Toolboxtopics.com
Confined Spaces - OSHA (US)
Confined Space - Introduction - CCOHS (Canada)
Confined Space Hazards - Numerous Links & Downloads
Confined Spaces: Myths, Magic, Urban Legends and the Facts - EHS Today
Confined Space Entry: Why Ventilate? - EHS Today
Confined Space Rescue - COMMUNICATION TO THE RESCUE - EHS Today
Hazardous Gases Arising from Cutting and Welding 
Surveying Confined Space Hazards - EHS Today

Downloads:   (Right-click to "Save Target As" in IE or "Save Link As" in Firefox for PDF files)

A Guide to Safety in Confined Spaces - US Dept of Labor / North Carolina, U.S. (pdf)
Confined Spaces - HSE INDG258 (pdf)
Confined Space Safe Practice - IACS (pdf)
Confined Spaces and Welding - American Welding Society (pdf)
Confined Space Guide - California State University (pdf)
Confined Spaces - Entering and Working In - Oklahoma State University (pdf)
Health and Safety Fact Sheet - Confined Spaces - AFSCME
Safe Working in a Confined Space - New Zealand Department of Labour (pdf)
Work in Confined Spaces - Swedish National Board of Occupational Safety and Health (pdf)
Working in Confined Spaces: Criteria for a Recommended Standard - NIOSH, 1979 (pdf)