Highly dangerous slurry gases pose unpredictable risk
BACKGROUND:Slurry gases are heavier than air and so they displace oxygen, putting anyone entering a slurry tank without breathing equipment in danger of suffocation
MULTIPLE DEATHS involving a slurry tank incident are rare but the tanks have been linked to 11 deaths in the Republic between 2006 and 2010. A further 12 people died in slurry-related incidents between 1996 and 2005.
Animal waste has to go somewhere, and more than 40 million tonnes of this slurry is stored and spread every year in the State.
For environmental reasons slurry cannot be spread in the winter months, because the rain could wash it into water sources. Most farms now have slatted sheds which allow the animal waste to go through the slats into large tanks underneath.
Teagasc health and safety officer John McNamara said manholes providing access to the tanks had been placed outside most slatted sheds since the early 1990s for health and safety reasons. Farmers need access to the tanks to agitate the slurry so the surface crust is broken and the waste has a uniform consistency. It is then removed by a slurry tanker for spreading.
Mr McNamara said the tanks were dangerous for two reasons. Drowning is the most common cause of death involving slurry but people have also died from gas poisoning. The decaying waste produces a mix of gases such as hydrogen sulphide, methane and carbon dioxide.
Hydrogen sulphide smells like rotten eggs at low levels but cannot be smelt at higher levels. According to the Health and Safety Authority, just one breath or lungful at this level could cause instant death.
The gases are released when the slurry is agitated. Mr McNamara said he always advised farmers to “evacuate and ventilate before you agitate” even if the manhole providing access to the tank was outdoors.
Because of the unpredictable nature of the gases, he said there was no safe place anywhere in the vicinity of the tank, so animals should be removed and the farmer should stand at a safe distance during agitation. He also said farmers should not agitate slurry in calm weather.
Despite the well-publicised warnings about never entering a slurry tank, he said he received many calls from farmers who wanted to retrieve items such as a loose slat, or even an animal, from the tanks.
“The clear advice is to never go into a tank,” he said. Because the gases are heavier than air, they displace oxygen, so anyone entering a tank could suffocate.
Attempting to rescue someone from a tank was impossible without breathing apparatus, a winch and two able-bodied people, he said.
Farmers’ associations North and South of the Border have come together to express sympathy to the Spence family. Irish Farmers’ Association president John Bryan said the entire farming community was shocked by the tragedy.
“On behalf of our members, I want to convey our deepest sympathies to the family following this terrible accident,” he said, adding that he had been in contact with the Ulster Farmers’ Union to express his condolences.
Ulster Farmers’ Union president Harry Sinclair said his members extended their deepest sympathies to the family.