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Occupational Health & Safety Resource Kit. Proudly brought to you by CEPU: NSW Telcommunications & Services Division |
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The hazards encountered when entering
and working in confined spaces, such as cable pits, are capable of causing bodily injury, illness and death amongst telecommunications workers.
Accidents occur primarily because of the failure to recognise that a confined space is a potential hazard. It should therefore be considered that the most unfavourable situation exists in every case and that the danger of explosion, poisoning and asphyxiation will be present at the onset of entry. CEPU members sometimes work in confined space environments such as cable pits, ducting, sub-floor crawl spaces, cable vaults and manholes. Confined spaces are areas that have limited openings for entry and exit, plus unfavourable natural ventilation that could contain or produce dangerous air contaminants. Generally such areas are not intended for continuous worker occupancy.  |
Before forced ventilation is initiated, information such as restricted areas within the confined space, voids, the nature of the contaminants present, the size of the space, the type of work to be performed and the number of people involved should be considered. The ventilation air should not create an additional hazard due to recirculation of contaminants, improper arrangement of the inlet duct, or by the substitution of anything other than fresh (normal) air
It is important to note that the pungent smell of hydrogen sulphide, or rotten egg gas, did not act as a warning to the people who died. The stench of rotten egg gas is obvious at lower concentrations but it cannot be smelt at higher, more dangerous levels because the sense of smell can quickly be overcome.
(approximately 20.9% oxygen, 78.1% nitrogen, and 1% argon with small amounts of various other gases). The terms air and oxygen are sometimes considered synonymous. However, this is a dangerous assumption, since the use of oxygen in place of fresh (normal) air for ventilation will expand the limits of flammability and increase the hazards of fire and explosion.
Types of Confined Spaces Gases that are heavier than air (hydrogen sulphide – H2S – butane, propane, and other hydrocarbons) remain in depressions and will flow to low points where they are difficult to remove. Therefore, these gases (heavier than air) are a primary concern when entry into such a confined space is being planned. Other hazards may develop due to the work performed in the confined space or because of corrosive residues that accelerate the decomposition of scaffolding supports and electrical components. Because some gases are odourless, the hazard may be overlooked with fatal results. Gases that are lighter than air may also be trapped within an enclosed type confined space, especially those with access from the bottom or side. There have been six fatalities as a direct result of exposure to toxic gas in confined spaces in four separate accidents recently in New South Wales. In each case the gas was generated by microbial action on products that contained protein or starch. The gas produced was the highly toxic hydrogen sulphide, commonly known as rotten egg gas. |