What is a Confined Space?
Confined Space refers to any place, including any vessel, tank, container, pit, bund, chamber,
cellar or any other similar space which, by virtue of its enclosed nature, creates conditions that
give rise to a likelihood of an accident, harm or injury of such a nature as to require emergency
action due to:
- The presence or reasonably foreseeable presence of:
– flammable or explosive atmospheres
– harmful gas, fume or vapour
– free-owing solid or an increased level of liquid
– excess of oxygen
– excessively high temperature
- The lack or reasonably foreseeable lack of oxygen
A toxic atmosphere may cause various acute effects, including impairment of judgement, unconsciousness and death. A toxic atmosphere may occur due to the presence or ingress of hazardous substances. These substances may be present in the Confined Space for various reasons such as:
- Remaining from previous processing or storage
- Arising from the disturbance of sludge and other deposits
- The presence of a fire or flames within the space
- Seepage from improperly isolated adjoining plant
- Formation during the work processes carried out in the space
- Being released from under scale and in brickwork as a result of the work process.
Oxygen can be lacking a confined space for the following reasons:
- Displacement of air by another gas
- Various biological processes or chemical reactions (such as rotting of organic matter, rusting of metals, burning, etc)
- Absorption of air onto steel surfaces, especially where these are damp
An excess of oxygen, in the presence of combustible materials, results in an increased risk of fire and explosion. Some materials, which do not burn in air, may burn vigorously or even spontaneously in an enriched oxygen atmosphere.
Flammable or Explosive Atmospheres
A flammable atmosphere presents a risk of fire or explosion. Such an atmosphere can arise from the presence in the confined space of flammable liquids or gases or of a suspension of combustible dust in the air.
If a flammable atmosphere inside a confined space ignites, an explosion may occur, resulting in the expulsion of hot gases and the disintegration of the structure.
Flowing Liquid or Free Flowing Solids
Liquids or solids can flow into the confined space causing drowning, suffocation, burns and other injuries. Solids in powder form may also be disturbed in a confined space resulting in an asphyxiating atmosphere.
The enclosed nature of a confined space can increase the risk of heat stroke or collapse from heat stress if conditions are excessively hot. The risk may be exacerbated by the wearing of personal protective equipment or by lack of ventilation.