On 5 March 2015 we discussed the Third edition of the Confined Spaces Regulations 1997, published in December 2014, and its recommendations for hypoxic environments. Hypoxic environments are those in which the oxygen level is deliberately lowered – for example to reduce the risk of fire or to minimise oxidation in fresh produce. This post looks at the risks of non-deliberate oxygen depletion in confined spaces either as a by-product of industry or as a consequence of natural processes.
According to the Regulations 1997, a confined space is ‘…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’. Furthermore, for an area to be classed as a confined space it must be ‘…substantially (though not always entirely) enclosed’, and, ‘one or more of the specified risks must be present or reasonably foreseeable’.
Some spaces which are normally considered safe may be quickly compromised by any activity that consumes oxygen. Welding is a good example – particularly where it employs a shielding gas such as argon to protect the weld from contaminants in the air. Argon is an inert gas which is naturally present in the atmosphere, but when used in concentrated form in a confined space it has the potential to deplete the oxygen. Ventilation and personal oxygen monitors are essential in these situations.
Eight tragic accidental deaths a year
Nitrogen, another inert gas, also has the potential to deplete oxygen. As a widely used industrial and process gas it causes approximately eight accidental deaths each year in the United States. Incidents in the UK are less common but still occur periodically – disaster was averted in February this year when a 200-litre nitrogen tank was discovered to be leaking at St Columb Major Industrial Estate, Newquay. Only weeks earlier a nitrogen leak killed two workers at a factory in South Korea.
Just a few of nitrogen’s many uses include food processing, manufacturing, purging, cryogenics, medical procedures and the transport industry. It is used in medical establishments, factories and laboratories. It is becoming popular in contemporary cooking (molecular gastronomy) as a result of innovative culinary techniques. Some plumbers use nitrogen for freezing and isolating pipes. Air conditioning installers use nitrogen for purging refrigerant pipelines during brazing to prevent oxidation.
Oxygen depletion can also result from microbiological activity; organic materials such as wood pellets, chips and logs present a hazard during both transport and storage. Ships’ cargo holds are a known risk and wood products have been found to deplete oxygen within days. In May 2014 three fatalities on a cargoship in Goole, UK, were attributed to oxygen depletion. Large fuel stores for wood boilers are at risk not only from oxygen depletion but also from gases such as carbon monoxide and carbon dioxide. Some of these hazards will be discussed in more detail later.
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Author: Paul Smith
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