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Industrial Rescue: What is a Confined Space?

The Health and Safety Executive (HSE) Confined Spaces Regulations 1997 give a definition of ‘confined space’.

It is defined as: “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”.

But what does this mean?

Basically, even though a space is or isn’t totally enclosed, it is only defined as a ‘confined space’ if one or more of the foreseeable specified risks are present, or could be.

It doesn’t necessarily have to be a small space either, or restricted.

Therefore the ‘confined space’ has two defining features:

  • It must be a space that is substantially (though not always entirely) enclosed.
  • One or more of the specified risks must be present, or reasonably foreseeable, when considering the space and/or the work to be undertaken.

What is a specified risk?

The 1997 Regulations define a ‘specified risk’ as one or more of the following:

  • Serious injury to any person arising from a fire or explosion.
  • A loss of consciousness of any person at work arising from an increase in body temperature.
  • A loss of consciousness or asphyxiation of any person at work arising from gas, fume, vapour or lack of oxygen.
  • The drowning of any person arising from an increase in the level of liquid.
  • The asphyxiation of any person arising from a free flowing solid or the inability to reach a breathable environment due to the entrapment by a free flowing solid.

These hazards may be naturally present or may be introduced when doing work in a confined space.

There are two classifications in use generally in the United Kingdom. These are the NOS (National Occupational Standards) and the Water Sector’s own system created by Water UK(the umbrella organisation representing major water and waste water service providers in the UK).

National Occupational Standards (NOS)

The NOS classifications give us the ‘low risk’, ‘medium risk’ and ‘high risk’ levels as trained on the City & Guild courses.

  • Working in low risk: An  environment with low risk entry with adequate natural or mechanical ventilation. Access appears simple, unobstructed and with no likely risk of  flooding.
  • Working in medium risk: A specified hazard may be present, it will require the use of escape breathing apparatus. One or more people outside the space controlling entry and dealing with emergencies.
  • Working in High risk: Non standard entry which may make rescue difficult. Hazards likely to be present and the entry may be complex.

Specific control and emergency arrangements must be made and all entrants have to make use of breathing apparatus and detection equipment. Additional staff with appropriate rescue training will be necessary for dealing with emergencies.

The NC System (Water UK)

  • NC1: Low risk with a shallow entry. It has adequate natural or mechanical ventilation. Access to the space is simple and unobstructed. No likely risk of flooding.
  • NC2: It has a vertical access that is unobstructed. The entrant is permanently attached to the hoist or similar device while i the space.
  • NC3: Entrants working away from the entrance shaft so not permanently attached.
  • NC4: non standard entry which may involve complex operations. It may also contain additional risks and therefore require additional specific control measures and rescue arrangements.

Water UK state that a classification assigned to the confined space is determined by a combination of risk assessments and physical characteristics of the actual work job being undertaken. This means classifications can change dependent on the risk assessment findings and conditions encountered.

For all work in confined spaces a full risk assessment, method statement specific for that job and emergency arrangements need to be in place and signed by all entrants. This forms part of your safe systems of work.

Red Kite SAR has staff trained and experienced to work in confined spaces alongside your staff as part of your emergency plans and safe systems of work.

Contact Us to see how we can help you.


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