How cattle waste can become a killer
A slurry tank or pit collects the waste products from cattle underneath the sheds where the animals are housed during the winter.
Farmers use this mixture of manure and water as a fertiliser on the land in the early months of summer to help create silage for the herd for the coming winter.
Before it can be spread, farmers have to stir or agitate the mixture, which forms a thick crust over the winter months.
It is this mixing process which can prove fatal to anyone in close proximity when noxious gases are released into the air.
Slurry gas is a mixture of methane, carbon dioxide, ammonia and hydrogen sulphide, which are produced by bacteria during the decomposition of slurry.
All these gases are unpleasant; some are also poisonous as well as being flammable, with hydrogen sulphide the most dangerous of all to adults and animals.
The Health and Safety Executive (HSENI) says that a high concentration of hydrogen sulphide disrupts the sense of smell, causing difficulty in breathing, then disorientation. After only a few breaths, collapse and death can follow.
Hydrogen sulphide is deadly because it rapidly displaces air from the lungs and affects the nervous system.
HSENI says that during mixing the rate of gas release is variable and difficult to predict, adding to the danger. As the gas is generally given off in large volumes very soon after mixing starts in any area of the tank, the first 30 minutes of the process are the most dangerous.
The experts advise that children and animals should be kept away from the slurry mixing shed, mixing should be done on a windy day, and that all doors and windows should be kept open throughout the entire process.