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Slurry Spreading Northern Ireland – Mixing Slurry Safely

30 January 2019

In the panic to get it out into the field, it can be easy to overlook the extreme risks that slurry mixing and spreading can pose, particularly that of slurry gas. We spoke to Kevin Campbell, an inspector with the HSENI's Major Investigation Team about the dangers of slurry gas and what farmers can do to help prevent tragedy.

Slurry Gas Explained


Slurry gas is a toxic mixture of gases created as a by-product of the fermentation of slurry. The most dangerous of these is hydrogen sulphide, which can quickly overcome and kill farm workers and livestock, even in the open air.

The gas is heavier than air and so has a tendency to linger around slurry pits, can knock out your sense of smell at higher concentrations and quickly displaces air from the lungs, meaning that only one breath can be enough to be fatal.

As soon as the mixing of slurry begins, the gas is released rapidly and in large quantities just like when a bottle of fizzy drink is shaken and then opened. It can also be responsible for multiple fatalities if attempts are made to rescue farm workers who have been overcome by the fumes.

Slurry Gas Safety Tips


  • The dangers posed by slurry gas should never be underestimated, however the HSENI advises that there are certain steps that farmers can take to ensure the safety of themselves, their employees and their livestock.
  • All animals should be removed from the building and from nearby sheds. Slurry gas is just as deadly to animals as it is to humans and is responsible for a large number of livestock deaths each year. Children should never be allowed in the area when working with slurry.
  • Ensure that any exposed areas around the slurry tanks or pits are covered to prevent anything or anyone from falling into them.
  • Naked flames should never be near slurry, as the slurry gas mixture is highly flammable. 
  • Outside mixing points should be used first and, if possible, farm workers should try mix slurry on a windy day as the breeze will help better disperse the slurry gas. Windows and doors should be opened to ensure good airflow around the building.
  • Slurry gas is at its highest concentrations for the first half-hour after mixing begins, so once the mixer is set you should leave the area entirely and take a break for 30 minutes or so before returning.
  • If possible, try to mix the tank where there's at least one foot of space between the top of the slurry and the slats. The heavy nature of the gas means that it will settle over the slurry and take up less space in the building.
  • Be aware that bending down to the level of the gas cloud for even a few seconds could cause you to lose consciousness.
  • If it's necessary to move the pump or change its direction, you should again leave the building and not re-enter for at least another 30 minutes, as the change in position will unsettle gas still dissolved in other parts of the slurry.
  • If you have to go back into the shed for any reason, always make sure that you have someone with you to call for help in the event of an accident. Farm workers should never enter buildings on their own when slurry is being mixed.
  • Be aware that face masks and filter-type masks are of no use. No-one should ever enter a slurry tank unless they have a breathing system with its own closed air supply, and this should only ever be left up to a trained professional with properly maintained equipment. 

What To Do In An Emergency


  • Dial 999 and make sure they know that slurry gas is present to ensure the emergency services can bring the right equipment to deal with the situation.
  • If possible, stop the slurry pump and get the person affected by the slurry gas to fresh air.
  • Never put yourself or other employees at risk to rescue other farm workers, as many people have died trying to save others.