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Confined Spaces

Hazard Related Topics


Confined spaces can contain hazards which are undetectable by eye and therefore access during the construction process can be doubly hazardous as the normal senses may give no warning.

The best way to guard against the hazards of working in such spaces is to design them out.

The term 'Confined Space' has a wide application. Some situations are fairly obviously confined spaces:

  • Closed Tanks
  • Large Ducts
  • Sewers and Pipelines
  • Enclosed Drains
  • Manholes
  • Reaction Vessels
  • Trenches

Others are less obvious but can be equally dangerous because of the accumulation of gases and the lack of air circulation even though the door is left open, or because the person carrying out the work could be engulfed in a free flowing solid such as sand or grain.

  • Tanks and Vats, particularly where heavier than air gases or vapours may be present
  • Closed and unventilated rooms or roof spaces
  • Underground sub-stations and other plant rooms
  • Medium sized and large furnaces and ovens
  • Cable tunnels
  • Silo's used for the storage of grain, sand etc.

Any confined space must be identified in the Health and Safety Plan and the Health and Safety File. The design must provide a safe means of access to and egress from a confined space. If a method of naturally or artificially ventilating the confined space cannot be provided, this must be identified.

The Contractor must comply with the Confined Spaces Regulations 1997 and the inspection procedures laid down in the Construction (Design and Management) Regulations 2015. The Confined Spaces Regulations 1997 lay down the precautions which must be taken.

The Hazards

Working in confined spaces can be particularly hazardous for the following reasons:

  1. Air in the confined space is made un-breathable by poisonous gases. Some poisonous gases are introduced naturally by the seepage of gases into the space from contaminated land, a natural gas build up in sewers and manholes or by the disturbance of slurries or liquids which can lead to a sudden build up of gas. Remember that some gases can be highly flammable and therefore can be ignited easily.
  2. Oxygen can be depleted in the space by rust inside tanks or vessels eating up the oxygen or the chemical reaction of some soils and air causing oxygen depletion.
  3. Vapours can build up in the confined space because of the work done in them. Petrol or diesel engines give off exhaust gases which are poisonous and some paints and glues give off hazardous vapours.
  4. Working space can be so restricted that it can bring workers into contact with other hazards in the form of moving machinery, electricity or steam pipes or vents.
  5. Access might be so restricted as to make escape or rescue attempts extremely difficult.
  6. Individual workers may panic in a confined space thus making rescue more hazardous.


As stated earlier the best way of dealing with the hazards of confined spaces is to design the structure without them. However if this is not possible then access should only be allowed after the following precautions have been taken:

  1. Consider whether the space could be altered to make it permanently safe or the work could be changed to make entry unnecessary. Only if it is not reasonably practicable to carry out the work without entering the space should entry be undertaken.
  2. Identify the work to be done and what the hazards are.
  3. Introduce a system of work which renders the work safe and without risks to health, and ensure everyone understands it. It may mean the introduction of a permit to work system.
  4. Ensure that the confined space has enough ventilation to make the air fit to breathe. If necessary introduce mechanical ventilation.
  5. Ensure that the workers have been trained in the dangers and precautions including rescue procedures.
  6. Ensure the entrance is big enough to allow workers with necessary equipment access and egress.
  7. Ensure that the atmosphere inside the space is tested and tests continue during the course of the work.
  8. Ensure workers inside the space wear safety harnesses and lifelines, and, if it is not possible to ensure a good supply of clean air, breathing apparatus.
  9. It is imperative that a responsible person is constantly stationed outside the space to communicate with those inside, raise the alarm if necessary and take charge of any rescue operations.
  10. Ensure that a suitable and sufficient method of rescue is in place and that it ensures the health and safety of any person responsible for putting the rescue arrangements into operation.
  11. Where there may be a need for resuscitation any equipment necessary to enable the resuscitation to be carried out must be provided and maintained.

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