A ‘confined space’ is:
- first, a place which is substantially (though not always entirely) enclosed; and
- secondly, one where there is a reasonably foreseeable risk of serious injury from hazardous substances or conditions within the space or nearby.
Examples of places which can meet the definition of a confined space include chambers, tanks, vats, silos, pits, trenches, sewers, flues, plant rooms, enclosures (even temporary ones) and wells.
The main hazardous substances or conditions that can cause serious injury or death in these places include:
- fire or explosion;
- loss of consciousness due to an increase in body temperature;
- loss of consciousness or asphyxiation from gas, fume, vapour or lack of oxygen;
- drowning due to a rise in liquid level; and
- asphyxiation because of a free-flowing solid.
One of the high-risk characteristics of a confined space is that changes in conditions can occur extremely quickly. This feature is one of the reasons why any work in a confined space:
- should be closely monitored at all times by a person trained to respond immediately in an appropriate manner; and
- should be supported by competent personnel with appropriate equipment and facilities to make an immediate rescue, should the need arise.
The two main aspects of confined spaces are summarised in Summary Sheet A3.
HSE leaflet Safe Work in Confined Spaces INDG258 and Approved Code of Practice (ACoP) L101 Safe Work in Confined Spaces offer more detailed advice and guidance.