1.1.13 Confined spaces

A confined space is a place which is substantially enclosed (though not always entirely), and where serious injury can occur from hazardous substances or conditions within the space or nearby (e.g. lack of oxygen).

Confined spaces can be deadly

A number of people are killed or seriously injured in confined spaces each year. This happens in a wide range of industries, from those involving complex plant to simple storage vessels. Those killed include people working in the confined space and 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 (e.g. 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

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 the following issues.

  • 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
    • 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
  • Poisonous gas, fume or vapour. These can:
    • Build-up in sewers and manholes and in pits connected to the system
    • Entering tanks or vessels from connecting pipes
    • Leaks 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 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 from 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 from 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 to decide what measures are necessary for safety. 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
Work in confined spaces according to Government Notice. R: 1031 of 30 May 1986

5.  (1)  An employer or a user of machinery shall take steps to ensure that a confined space is entered by an employee or other person only after the air therein has been tested and evaluated by a person who is competent to pronounce on the safety thereof, and who has certified in writing that the confined space is safe and will remain safe while any person is in the confined space, taking into account the nature and duration of the work to be performed therein.

(2)  Where the provisions of subregulation (1) cannot be complied with the employer or user of machinery, as the case may be, shall take steps to ensure that any confined space in which there exists or is likely to exist a hazardous gas, vapour, dust or fumes, or which has or is likely to have, an oxygen content of less than 20 per cent by volume, is entered by an employee or other person only when–

(a)  subject to the provisions of subregulation (3), the confined space is purged and ventilated to provide a safe atmosphere therein and measures necessary to maintain a safe atmosphere therein have been taken; and

(b)  the confined space has been isolated from all pipes, ducts and other communicating openings by means of effective blanking other than the shutting or locking of a valve or a cock, or, if this is not practicable, only when all valves and cocks which are a potential source of danger have been locked and securely fastened by means of chains and padlocks.

(3)  Where the provisions of subregulation (2)(a) cannot be complied with, the employer or user of machinery shall take steps to ensure that the confined space in question is entered only when the employee or person entering is using breathing apparatus of a type approved by the chief inspector and, further, that–

(a)  the provisions of sub-regulation (2) (b) are complied with;

(b)  any employee or person entering the confined space is using a safety harness or other similar equipment, to which a rope is securely attached which reaches beyond the access to the confined space, and the free end of which is attended to by a person referred to in paragraph (c);

(c)  at least one other person trained in resuscitation is and remains in attendance immediately outside the entrance of the confined space in order to assist or remove any or persons from the confined space, if necessary; and

(d)  effective apparatus for breathing and resuscitation of a type approved by the chief inspector is available immediately outside the confined space.

(4)  An employer or user of machinery shall take steps to ensure that all persons vacate a confined space on completion of any work therein.

(5)  Where the hazardous gas, vapour, dust or fumes contemplated in subregulation (2) are of an explosive or flammable nature, an employer or user of machinery shall further take steps to ensure that such a confined space is entered only if —

(a)  the concentration of the gas, vapour, dust or fumes does not exceed 25 per cent of the lower explosive limit of the gas, vapour, dust or fumes concerned where the work to be performed is of such a nature that it does not create a source of ignition; or

(b)  such concentration does not exceed 10 per cent of the lower explosive limit of the gas, vapour, dust or fumes where other work is performed.

(6)  The provisions of this regulation shall mutatis mutandis also apply, in so far as they can be so applied, to any work which is performed in any place or space on the outside of and bordering on or in the immediate vicinity of, any confined space, and in which place or space, owing to its proximity to the confined space, any hazardous article, oxygen-deficient atmosphere or dangerous concentration of gas, vapour, dust or fumes may occur or be present.

Is a ‘permit-to-work’ necessary?

A work permit is legally required in all cases where work is performed in confined spaces.