[ Introduction ]
[ Industrial Accident of Confined Space ]
[ Industrial Accident of Chemicals ]


Level 1 Level 1 Level 1



A confined space means any place in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk of fire or explosion; loss of consciousness of any person due to an increase in body temperature; loss of consciousness or asphyxiation of any person due to gas, fume, vapour or lack of oxygen; drowning of any person due to an increase in the level of liquid; or asphyxiation of any person who is trapped by a flowing solid.

Confined spaces include any chamber, tank, vat, pit, well, sewer, tunnel, pipe, flue, boiler, pressure receiver, hatch, caisson, shaft or silo.


Hazards Identification

1. Deficiency of Oxygen in Air
    Air generally comprises 21 % oxygen. However, in the following conditions, the oxygen in the air may decrease, resulting in a menace with human life:
      - Chemical reactions caused by oxygen consumption
      - Oxygen is consumed due to oxidation during such processes of welding, cutting by oxyacetylene, rusting, naked flame operations, fermentation and moulding.
      - Substitution
      - Oxygen is squeezed out by such inert gases as nitrogen, argon and carbon dioxide.
      - Adsorption on surface
      - Oxygen is adsorbed by porous surfaces, such as activated carbon.
    Changes of the oxygen content in air that is breathed in, can cause the following adverse physical reactions to the human body:



2. Flammable Spaces
    Flammable gas in a confined space can lead to explosion or fire. A space becomes flammable when oxygen in the air mixes with flammable gases, vapours or dust. These gases and vapours may be formed by residues mixed with flammable substances, the use of flammable substances, or chemical reactions (e.g. the formation of methane).

    A space may also become flammable when combustible dust abounds or flows in the air when disturbed. Dust may come from agricultural products e.g. flour, chemicals, plastic particles, medicine or metal powder.
    Flammable spaces will explode when contact with igniting sources such as welding sparks or sparks from portable electrical appliances.
    Chemical Substances
      The principal means of encountering chemical substances include respiration, skin absorption and eating. The effects brought by chemical substances upon the human body may be chronic or acute, depending on the period of contact, the intensity of the hazards during contact and the impact of such hazards on health, for example, corrosive, toxic or harmful.
      Some poisonous gases emit a particular odour, like the smell of a rotten egg for hydrogen sulphide; whereas some toxic gases are odourless, like carbon monoxide, which is both colorless and odourless. In addition, the unpleasant smell of some toxic gases like hydrogen sulphide is likely to anaesthetise one's sense of smell soon after contact so that one may no longer sense its existence. Therefore, only the use of scientific equipment is reliable to measure the existence of chemical.
    Physical Hazards
      1. Mechanical hazards
        - Some dangerous components such as belts, rotation shafts and gears in equipment may cause harm when used.
      2. Electrical hazards
        - The risk of death caused by electric shock or getting burnt may arise when touching electric cables, electric wires and transformers in confined spaces or using electrical appliances in wet spaces.
      3. Noise hazards
        - Noise produced when working in confined spaces is generally higher than normal, leading to impairment in workers' hearing and may even lead to deafness.
      4. Radiation hazards
        - Sparks produced when using radioactive equipment in confined spaces may cause harm, such as laser or welding sparks.
      5. Environmental hazards
        - Extremely high or low temperature, dampness, wet spaces environmental conditions are more likely to pose danger in confined spaces.
      6. Transportational hazards
        - Since the entrance and exit of some confined spaces, such as sewers, are situated on pavements or roads, workers will have the risk of being knocked down by vehicles passing by. There is also risk of people falling down into the confined spaces.
      7. Engulfment by liquid or flowing solids
        - The risk of drowning arises when the confined space is waterlogged or when water or other liquid suddenly pours in. In addition, flowing solids such as silt or cereals may pose the risk of engulfment.
    Other Hazards
      1. Hazards from manual operations
        - The working environment of confined spaces is generally narrow and workers inside need considerable effort when performing manual operations. The use of personal protective equipment may also increase the difficulty of performing manual operations.
      2. Biological hazards
        - Workers may be infected with different varieties of bacteria and viruses and even threatened by biological hazards produced by insects and snakes.