Slurry Gas Detection - CoGDEM Comment

CoGDEM (UK) is the Council of Gas Detection and Environmental Monitoring, a trade association with a membership of over fifty companies involved in the gas detection industry. We are pleased to have ILM/ETP (the publishers of this IET magazine) as an Associate Member, so we now place a regular column of news from the gas detection industry in IET magazine.

The risk of hazardous gases in agricultural workplaces has been highlighted once again after the tragic death in June 2014 of a farmer’s young son in Northern Ireland due to inhalation of toxic slurry gases.  The disposal and storage of animal waste will generally always lead to the production of various gases, including methane, carbon dioxide, hydrogen sulphide and ammonia.  These gases can remain trapped within the liquid waste until it is agitated by mixing, pumping, stirring or similar activities which can allow the gases to be released into the surrounding air.  In confined spaces these gases can build up to reach harmfully toxic concentrations, and in some circumstances they can also displace the normally fresh air to produce an oxygen deficient atmosphere capable of asphyxiation.

After a member company spotted an error in a news report about the Northern Ireland fatality, CoGDEM arranged to be interviewed on BBC Radio Ulster to put the record straight about the detection of slurry gases.  It pointed out that in a perfect world, nobody should enter any space where slurry is being stored or treated, such areas should be well ventilated and signposted, with access doors or gates locked to prevent accidental entry. But if entry is unavoidable, for example to clean a tank that has just been emptied, or to manually clear a blockage, then farm workers must be made aware of the risk of atmospheric contamination. Normal precautions for confined space entry should of course be followed, and the worker should use a gas detector to check the air quality prior to entry and monitor it throughout the duration of the work.

It is not expected that all farmers will own a portable multi-gas detection instrument and have it ready for any such eventuality, but the interview was intended to let farmers know of the existence of such apparatus (as used routinely by Fire & Rescue Services), and that hire companies stock such products so that they can be rented during periods of planned maintenance or short-notice activities. Robust and reliable gas detectors can be invaluable life-saving companions, as they are in many industries facing gas hazards every day.

The interview also covered other points about slurry gas, such as the misconception that it will always be heavier than air. Two of the component gases, methane and ammonia, are considerably lighter than air, so these could well be present at the top of a stairway leading down to a slurry pit underneath a cowshed, for example. It was also pointed out that workers should not rely on their sense of smell to alert them to the presence of slurry gas, as gases such as hydrogen sulphide that produce a characteristically unpleasant odour can knock out a person’s ability to smell when the concentration becomes high enough.