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Safe Work in Confined Spaces guidance
Make sure you know what to do when working in confined spaces.

Working in confined spaces – gas monitoring advice from the HSE

In December 2014 the UK’s Health and Safety Executive (HSE) published the Third Edition of its Approved Code of Practice, ‘Safe work in confined spaces’. This updates the Confined Spaces Regulations 1997 with revised definitions and new examples. Of particular interest to Analox is the latest guidance on hypoxic (reduced oxygen) environments employed in fire suppression and food processing.

Gaseous fire suppression systems typically contain carbon dioxide (CO2) or a blend of inert gases, usually nitrogen and argon. These systems are used either to maintain a reduced oxygen level to prevent ignition (for example in libraries) or to extinguish a fire should one be detected. Where fire suppression gases are stored in cellars or plant rooms, these become by definition ‘confined spaces’.

In addition to the use of hypoxic areas for fire suppression purposes, they are also used in the food industry to reduce oxidisation and improve storage. In both cases hypoxic areas have a known risk and are relatively easy to monitor using gas detection devices. (Suitable gas sensors for oxygen depletion and CO2 detection are the Analox O2NE+ oxygen analyser and A50 carbon dioxide analyser.)

Hypoxic environments present a serious hazard to human health. A slight increase in carbon dioxide from the normal atmospheric concentration of 0.04% can result in tiredness and increased breathing. A level of 3% can cause dizziness. If the concentration approaches 10% unconsciousness or even death may follow. Nitrogen and other inert gases may cause oxygen depletion which is equally dangerous.

Carbon dioxide and inert gases are colourless and odourless, and are detectable only with specialist oxygen sensors and carbon dioxide monitors (they are not detectable by the human senses). Additional complications arise from the fact that carbon dioxide is heavier than air and collects at low level. In the case of nitrogen, it is slightly lighter than air but when cold has a tendency to settle.

Leakage from gas bottles, pipeline delivery networks and machinery may be rare, but without reliable gas detection systems any leaks could go unnoticed. At the very least, anyone entering an area of potentially reduced oxygen or raised CO2 would benefit from a personal gas sensor such as the Analox Aspida. This has both an oxygen analyser and a carbon dioxide analyser. (There is no definitive test for nitrogen; nitrogen detection relies on the analysis of oxygen depletion.)

Both carbon dioxide and nitrogen are recognised causes of accidents and deaths associated with work in confined spaces. They are widely used as industrial and process gases and are a hazard for anyone working in close proximity to them. Statistics show a consistent pattern of confined space accidents across the UK, with an average of one fatality per year attributed to oxygen depletion.

For further information see Safe work in confined spaces, Confined Spaces Regulations 1997, December 2014, ISBN: 978 0 7176 6622 5, L101 (Third edition)

Author: Paul Smith, Technical Writer

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Founded in 1981, Analox Sensor Technology provides niche and custom gas detection solutions to industries including beverage and fast food, commercial diving and laboratories. Analox has over 325 years of collective, specialist electronics and software engineering expertise, as well as a worldwide distributor network. Contact us to see how we can provide expert gas monitoring solutions and help you achieve your goals.

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