With the closed period for spreading slurry coming to an end at midnight tonight 31 January, the Health and Safety Executive for Northern Ireland (HSENI) is reminding farmers to take extra care when working with slurry.

Mixing slurry can be a particularly dangerous job as slurry gas is released very quickly, and in large quantities, as soon as the mixing starts.

Slurry gas is a mixture of gases, including the extremely poisonous gas, hydrogen sulphide. Even a low concentration of hydrogen sulphide can knock out your sense of smell so you won’t even know it’s there. At higher concentrations you will rapidly find it harder to breathe and become confused - and at certain concentrations, just one breath can kill.

The first 30 minutes are the most dangerous, so it is important for farmers to leave the shed as soon as mixing starts - and to stay out for at least 30 minutes.

Reminding farmers of the dangers of mixing slurry, Malcolm Downey, Principal Inspector of HSENI’s farm safety team, said: “Before starting any job on the farm, including slurry mixing, take time to stop, think and safely plan the work ahead.

“Cover openings and keep children and animals far away during the slurry mixing process.  Stay out of the building for at least 30 minutes after the mixing starts and every time you move the pump or change the direction of mixing. Please be aware that if a tank is mixed before the end of the closed period and is then mixed again before the tank is emptied that gas can build up again even within a day or two and it is essential to stay out for at least 30 minutes once again.

“Do not take any chances when mixing slurry.  As the closed period comes to an end I urge farmers to reflect on the safe slurry mixing code, remembering that just one breath can kill.”

Slurry mixing code

keep children away from the area at all times when working with slurryif possible, mix on a windy dayopen all doorstake all animals out of the building before starting to mix slurryuse outside mixing points firstif slats are removed, cover exposed areas of the tank beside the pump/mixer to stop anything falling instart the pump/mixer – then get out and stay out of the building for as long as possible - at least 30 minutesany time you have to go into the building try to make sure that another adult knows what you are doing and can get help if necessaryif you have to re-enter to move the pump or change the direction of the pump, leave the building as soon as this is done – do not go back in for as long as possible – at least another 30 minutes


rely on filter type facemasks use gas monitors as a substitute for working safelyhave naked flames near slurry, as slurry gas mixture is flammablestand close to the exhaust of a vacuum tanker when it is being filled

If you find someone has been overcome during slurry mixing, If possible, stop the pump and get the person to fresh air but do not put yourself at risk in the process. If breathing is weak or stopped, artificial respiration may be effective. Contact the emergency services and seek immediate medical attention.

For more information about working safely with slurry or general farming health and safety issues please contact the HSENI helpline on: 0800 0320 121 or visit the farm safety topic page on the HSENI website:

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