Slurry has been in the news a lot recently, under tragic circumstances. Why is it so dangerous? The main culprit is the sudden release of gases during slurry mixing- Hydrogen Sulphide, Ammonia, Carbon Dioxide and Methane can create an explosive and sometimes deadly cocktail. These are the exact same gases you would encounter when working in the sewerage system, and you would heavily safe-guard from it. I recently attended a Confined Spaces training course and we were taken through the basics of working safely in these conditions.
The gases are heavier than air and will lie low to the ground. This is particularly dangerous on a still day when they will take longer to disperse. If you happen to bend down into a pocket, you may be rendered unconscious very quickly, and this has led to people drowning as they topple into the tank openings. One of the biggest dangers is how unpredictable the risk is as we cannot rely on our senses to determine whether the risk is present when we look at the nature of the gases;
• Methane is explosive at concentrations of 5-15%,
• Ammonia has a powerful odour, it is corrosive, causing severe damage to mucous membranes and at high concentrations will quickly cause severe breathing difficulties
• Carbon Dioxide, though non-toxic, it displaces oxygen resulting in asphyxiation.
• Hydrogen Sulphide poisonous, corrosive, flammable, it knocks out your sense of smell at concentrations of approx. 150ppm- lethal dose at approx. 700ppm.
To be safe with slurry, you really need to be prepared for the worst case scenario at all times;
• Wear breathing apparatus – a filter face mask will not protect you,
• Try to avoid mixing on still days, wind will help disperse the settled gases much more quickly,
• Keep people and animals away from the mixing site,
• Remember the start of the mixing process is the most dangerous,
• Keep all naked flames away from the mixing site
• Don’t rely on a gas monitor – only use it in conjunction with all other precautions, it will not alert you to a sudden release quickly enough.
If you happen to come across somebody rendered unconscious by slurry fumes- do not go to aid them unless you have breathing apparatus on and have checked for other likely dangers. It is very likely that the same gases that have rendered them unconscious will do the same to you. The best help you can give is to contact the emergency services immediately.
I’ve attached a link to a video made by a farmer who almost lost his life after exposure to slurry gases and, sadly, lost his son who had come to rescue him; http://vimeo.com/84947719
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