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Confined Space Entry

Published: 01st Jul 2006


"The plunge into this pit I had avoided by the merest of accidents, I knew that surprise, or entrapment into torment, formed an important portion of all the grotesquerie of these dungeon deaths...'Death,'I said, "any death but that of the pit!"'The Pit and the Pendulum, Edgar Allan Poe (1842)

Poe, whilst writing his classic short story, succeeded in conjuring up a vision of "the pit" as a deep, dark place full of grotesque fates for those unfortunate enough to enter. In the modern health and safety context, "the pit" is just one example of the broad range of confined space entry scenarios. All of which are capable of bringing injury, illness and death to the unaware, untrained, unassessed and the unprepared.

Before looking in more detail at confined space definitions and the hazards to be encountered, consider the following scenarios. Particular attention should be given to the type of confined spaces involved, the hazardous substances and their means of generation:

  • A recently hired worker at an alcohol and feed mash producing operation was hosing down the interior of a fermentation tank from outside the top opening. For some unknown reason, the worker entered the tank and died when he encountering an atmosphere of 6% Oxygen and 48% Carbon Dioxide. The worker had been on the job for only three weeks. His training had been primarily production related on-the- job training with very little emphasis on safety
  • A young flooring contractor was found semi-comatose in an unventilated room where he had been working laying vinyl floor tiles and using a solvent-based adhesive. Becoming so used to the strong solvent odour he subsequently became unaware of it. Failing to notice the building vapour concentration and accompanying narcotic effect until it had finally rendered him incapable of exiting the room
  • A worker was killed and another seriously injured when they were asphyxiated by nitrogen at an American chemical manufacturing plant. The incident occurred inside a temporary enclosure the workers had erected over the end of large open gas pipe, where the workers were conducting a black light/UV integrity inspection. The workers were not aware that the pipe was being purged with nitrogen, creating an oxygen-deficient atmosphere
  • In Australia, authorities issued a warning about working in poorly ventilated workplaces, following an incident in which seven men suffering from carbon monoxide poisoning were hospitalised. The casual workers had been re-packing pallets, when they all started feeling sick. Subsequent investigations revealed the cause to be carbon monoxide coming from an LPG forklift which had not been tuned properly operating in a room with limited ventilation

The scenarios shared chemical exposure as the specified hazard, but all had different means of generating the chemical exposure. In addition, the nature of the confined space in each case varied considerably encompassing, tanks, work rooms, and temporary as well as permanent structures. This variety, leads us into the realm of defining what constitutes a confined space.

Defining a confined space

There is no internationally agreed definition for a confined space, so exact definitions varying from country-to-country, or even from state-to-state. However, through comparison of several international definitions, applied by the Australia1, United Kingdom2, United States3 4 5and International Labour Office6 it is possible to see common elements.

The shared common elements show that confined spaces are fully or partially enclosed areas where there is a foreseeable specified risk. This is very close to the definition given in the UK Confined Spaces Regulations 1997 where:

'confined space'means any place, including any chamber, tank, vat, silo, pit, trench, pipe, sewer, flue, well or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk;

Some of these confined spaces are easily defined, clearly subject to regulation and can be appropriately sign posted in advance to provide warning, tank, pit, vat, sewer, etc. However, other confined spaces can be harder to spot. Everyday spaces, such as small poorly ventilated rooms, cupboards, and vehicles can all be "enclosed or partially enclosed'and become dangerous when combined with a specified risk, the example of the flooring contractor laying vinyl floor tiles.

Temporary workspaces, often created to serve specific transient roles, are another type of confined space that can be difficult control, weather protection; dark rooms to allow black light/UV inspection; temporary workshops or storage area are just some examples of transient installations.

Overall, confined spaces should be viewed as considerably more hazardous than normal unconfined workspaces. Alterations in conditions, that may seem minor, can immediately change the status of the confined space from innocuous to life-threatening. Because these altered conditions may be transient and subtle, they can also be difficult to recognise and to address.

These issues can be further complicated because confined space work generally occurs during construction, inspection, maintenance, modification, cleaning and refurbishment. Work that is often non-routine for an organisation, short in duration, non-repetitive and worst still unpredictable (perhaps occurring outside normal working hours).

Specified risks

The hazards encountered in confined spaces can include personal confinement, as well as structural, process, mechanical, bulk or liquid material, atmospheric, physical, chemical, biological, safety and ergonomic hazards. Many of the conditions produced by these hazards are not unique to confined spaces but are exacerbated by the involvement of the confined area. In other words, the confinement and close proximity of hazards can raise the risk.

In the UK, foreseeable specified risk is defined in the Confined Spaces Regulations 1997 as:

'specified risk'means a risk of -(a) serious injury to any person at work arising from a fire or explosion (b) without prejudice to paragraph (a) - (i) the loss of consciousness of any person at work arising from an increase in body temperature (ii) the loss of consciousness or asphyxiation of any person at work arising from gas, fume, vapour or the lack of oxygen (c) the drowning of any person at work arising from an increase in the level of liquid (d) the asphyxiation of any person at work arising from a free flowing solid or the inability to reach a respirable environment due to entrapment by a free flowing solid

At this stage, there is potential to rapidly become absorbed and focus in on specified risks. However, much can be gained by focusing on the general aspects of confined space risk management that help to remove, reduce or mitigate all areas of risk.

Who are the confined space victims?

Accident data indicates that victims of confined space accidents have a wide variety of occupations. While most are employees and contractors, as might be expected, victims also include engineering and technical staff, supervisors and managers, and emergency response personnel. Sadly, the human tragedy and high fatality rate for incidents involving confined spaces is in part a price that is often paid twice: once by those who initially enter and again by those who subsequently attempt rescue.

The ILO and OSHA estimate that worldwide, these accidents claim about 200 victims per year in industry, agriculture and the home. This is at best a guess based on incomplete data, but it appears to be applicable today. About two-thirds of the accidents resulted from hazardous atmospheric conditions in the confined space. In about 70% of these the hazardous condition existed prior to entry and the start of work. Sometimes these accidents cause multiple fatalities, some of which are the result of the original incident and a subsequent attempt at rescue. Rescue under these circumstances is psychologically stressful and can cause even well trained rescuers to attempt rescues that place the would-be rescuers in more danger than the initial victim.

Confined space awareness

Given the people who fall victim to confined space accidents, one of the best defences against unnecessary risks is an informed and trained workforce and an active programme for hazard recognition and management. Training and the development of skills to enable supervisors and employees to recognise potentially hazardous conditions is also essential. An up to date registers, or inventory, of known confined spaces detailing the type of space, location, characteristics, contents, hazardous conditions and so on can be an invaluable tool. However, risk control systems and training must be robust enough to acknowledge that in many circumstance confined spaces defy being inventoried because their number and type are constantly changing, such as with temporary structures.

Where the confined spaces occur with in a manufacturing or process operations they are readily identifiable, yet remain closed and inaccessible almost all of the time. Under certain conditions, a space may be considered a confined space one day and would not be considered a confined space the next.

A benefit from identifying confined spaces is the opportunity to sign them. A sign can enable employees to relate the term confined space to equipment and structures at their work location. The downside to the signing process includes:

  • Safety signs can go missing or be swamped by other warning signs in the work place
  • Some organisations may vast numbers of confined spaces causing great difficulty in consistently identifying them all
  • Fixed signs offer no benefit where the inventory of confined spaces is dynamic (portable signs/banners are excellent in this instance)
  • Too much reliance on signs for identification can cause dependence, leading to confined space situations being overlooked

Preventing the need for entry

Under the Confined Spaces Regulations 1997, the priority when carrying out a risk assessment is to identify the measures needed so that work in confined spaces can be avoided. If, in the light of the work to be done and the risks identified, it cannot be considered reasonably practicable to carry out the work without entering the confined space, then it is necessary to determine what measures need to be taken to have a safe system for working within the confined space.

Resource (in terms of time, money and ingenuity) spent identifying whether work can be done without the need for entry into a confined space can often pay considerable dividends.

As an example where you can clean a confined space, or remove residues from it, from the outside using water jetting, steam or chemical cleaning, long handled tools, or in-place cleaning systems you remove the need for entry. This can reduce the number of people required to complete the task, can reduce downtime on the equipment and can reduce ancillary costs, such as the need for complex scaffolding of working platforms inside the confined space.

New or substantially modified plant and equipment that must contain confined spaces offer opportunities to eliminate, or where this is not possible, to minimise the risk. Discussion with designers, manufacturers, importers, suppliers, erectors and installers should identify these opportunities, considering situations in normal use as well as construction, inspection, maintenance and cleaning.

Opportunities could include, sizing and locating manholes and nozzles to allow atmosphere testing, product sampling, or suitable cleaning and inspection access. In one design, a vessel that required regular cleaning with water jets was designed to allow the top quarter of the vessel to be lifted away using a crane. A platform situated at the right height for the water jetters allowed them to safely walk around the exterior of the vessel during cleaning, eliminating the need for entry.

Risk assessment

The most complex and difficult aspect in the confined space process is risk assessment. In the UK, the Management of Health and Safety at Work Regulations 1992 apply across all industries and all work activities. The principal duty, regulation 3, requires all employers and self-employed persons to identify the measures they need to take by means of a suitable and sufficient assessment of all risks to workers and any others who may be affected by their work activities (insignificant risks can be ignored)

Risk assessment identifies both hazardous and potentially hazardous conditions and assesses the level and acceptability of risk. The difficulty with these risk assessments occur because many of the hazardous conditions can produce acute or traumatic injury, many can be difficult to recognise and assess, and often change with changing conditions. Avoiding the need for entry, and the elimination or mitigation of risks during preparation of the space for entry is, therefore, essential for minimising the overall risk during work. Many organisations, industry federations and associations provide guidance specific to the confined space issues relevant to the activities of their members, examples include, the Chemical Industries Association, Asbestos Removal Contractors Association, and British Compressed Gases Association. This is an important aspect of confined space work as very often the danger is a result of the work being done - welding, painting, flame cutting, integrity inspection, the use of adhesives and solvents. These guidance documents can form an excellent starting point for both risk assessments and identifying suitable precautions to include in safe systems of work.

Before continuing, a brief word of caution on utilising "generic'confined space risk assessments. Given the varied nature of the risks faced in managing entries into a confined space, over reliance on generic risk assessments can be falsely reassuring. Unless conditions and activities can be guaranteed to remain constant, an unlikely scenario, generic risk assessments should at best be used as a starting point or template when assessing the specific risks of a given confined space entry.

Safe systems of work

The workplace precautions selected for inclusion in a safe system of work will depend on the nature of the confined space, the risk from the entry and the risks involved with any specific work being done in the confined space.

The Confined Space Regulations 1997, Approved Code of Practice, provides the practical differences between cleaning car interiors with solvents and completing welding work inside a chemical reactor vessel, or work in a sewer as examples of the different level of workplace precaution required.

Generally the safe system of work is a pre defined and agreed, sequence of operations relying on following risk control systems and applying workplace precautions. The work place precautions should identify the hazards, then assess and control the risks. For confined spaces this could involve a number of aspects under the regulations, the following list is not exhaustive:

Formal procedures for carrying out work processes

  • Entry into confined spaces (Access and egress)
  • Atmosphere testing (testing the atmosphere prior to entry and continuous monitoring of the workface)
  • Supervision
  • Competence for confined spaces working (including medical fitness)
  • Communications
  • Limited working time
  • Emergencies and rescue

Systems covering the use of safety equipment, guards and personal protective equipment

  • Testing/monitoring the atmosphere
  • Personal protective equipment (PPE) and respiratory protective equipment (RPE)
  • Lighting
  • Selection and use of suitable equipment
  • Portable gas cylinders and internal combustion engines
  • Gas supplied by pipes and hoses
  • Fire prevention/Smoking
  • Static electricity

Special applications

  • Gas purging
  • Ventilation
  • Removal of residues
  • Isolation systems for gases, liquids and other flowing materials
  • Isolation systems for mechanical and electrical equipment


At some time or another many places may become a confined space and fall under the coverage of the Confined Spaces Regulations 1997. Some are quite obviously confined spaces - tanks, ducts, trenches, borehole silos, manholes, furnaces, vats, pipelines, sewers and underground chambers. But serious accidents and fatalities have occurred in the past in less obvious places such as rooms, vehicles, floor and ceiling voids none of which were regarded as confined spaces prior to the work commencing. The keys to being aware of these "pit falls'are aware employees, avoiding the need for entry, good quality risk assessment, effective forward planning and safe systems of work. ?


  • Australian Standard Safe Working in Confined Space AS 2865 - 1995
  • Health and Safety Executive (HSE) Confined Spaces Regulations 1997
  • OSHA Confined Space Entry Standard (29 CFR 1910.146)
  • Safety Requirements for Working in Confined Spaces, ANSI Z117.1 - 2003
  • NIOSH - Criteria for a recommended standard "Working in Confined Spaces'80-106
  • International Labour Office (ILO), Encyclopaedia of Occupational Health and Safety -Confined Spaces

    Sources of further information

    "Complete Confined Spaces Handbook'John F. Rekus and Associates, National Safety Council, Riderwood, Maryland, USA.

    "Safety and Health in Confined Spaces'Neil McManus NorthWest Occupational H & S, Vancouver, Canada

    International Labour Office (ILO), Encyclopaedia of Occupational Health and Safety -Confined Spaces

    Australian Standard Safe Working in Confined Space AS 2865 - 1995

    Health and Safety Executive (HSE) Confined Spaces Regulations 1997, Approved Code of Practice L101

    OSHA Confined Space Entry Standard (29 CFR 1910.146)

    Safety Requirements for Working in Confined Spaces, ANSI Z117.1 - 2003

    NIOSH - Criteria for a recommended standard "Working in Confined Spaces'80-106

    Author/Company Details:

    Simon Peake is an occupational hygienist, member of the British Occupational Hygiene Society and works for Dow Corning Ltd. Also a qualified safety practitioner, he has over fifteen years experience of confined space entry issues in the chemical manufacturing industry. Dow Corning is a global leader in silicon-based technology and innovation, offering more than 7,000 products and services to over 25,000 customers worldwide.

    Occupational hygiene is about eliminating or controlling health hazards in the workplace (NOT about washing hands properly!), and the primary objective of the profession is to protect the long-term health and well-being of those at work. The British Occupational Hygiene Society (BOHS) is the definitive voice of occupational hygiene and has strong alliances with other health and safety organisations, the HSE, trade unions and business.

    BOHS was formed in 1953 and its aim is simple: to help to reduce work-related ill-health. With members from within industry, health, education and research, it is by far the biggest hygiene society in Europe, and has been strengthened by its merger in April 2003 with the British Institute of Occupational Hygienists. The Faculty of Occupational Hygiene within BOHS plays a vital role in developing and maintaining the professional standards of hygienists, and is recognised internationally as a major professional examination and qualification body.

    For further press information, contact Anthea Page, Communications Officer, by e-mail: or by telephone: 01332 250701.

    BOHS, 5/6 Melbourne Court, Millennium Way, Pride Park, Derby, DE24 8LZ

    Published: 01st Jul 2006 in Health and Safety International

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