Ventilate, evacuate and agitate – vital steps in safe handling of slurry
THE closed period for spreading slurry on land ended on January 15 and many farms will be hoping to get an opportunity – weather permitting - to spread slurry as levels in tanks may be quite high.
Prior to spreading slurry you will need to agitate it in the tank. Some safety precaution should be in place around this time to prevent accidents to both people and livestock.
Slurry gases are poisonous to both animals and humans. The gases given off by slurry contain carbon dioxide, ammonia, methane and hydrogen sulphide.
Hydrogen sulphide is the slurry gas of most concern as it is highly toxic.
If it is inhaled it is fatal in seconds to both animals and humans and as little as one breath can kill.
This gas smells like rotten eggs but it quickly overcomes the sense of smell which can give a false sense of security by giving one the impression that the gas has dissipated when it may not have done so.
The greatest release of slurry gas occurs when the crust of the slurry has been broken and for 30 minutes following this. Increased gas levels can occur following addition of silage effluent to tanks and also in the case of agitating slurry following storage for prolonged periods. Care needs to be taken at these times.
The safety precautions that should be taken around slurry agitation can be summed up by 3 words – VENTILATE, EVACUATE AND AGITATE.
Firstly don’t select a calm windless day to agitate as gases will need some wind to aid dispersal. Open all possible doors, feed gates and possible air outlets.
Evacuate all persons and animals from the building and prevent access by people to the site while agitation is taking place. Warn elderly persons, children and visitors that slurry agitation is taking place and the dangers involved – indeed it’s not a bad idea to put up a warning sign to make unexpected visitors aware that slurry agitation is taking place. Particular care should be taken that children are not in the vicinity of a shed during agitation of slurry.
Ideally slurry should not rise to within 30mm of slats. The slurry should be agitated from an upwind position with care being taken at the cover areas. It is a good idea to put temporary protection around cover openings to prevent farm pets or people falling into the tank.
It is not advisable to attempt a rescue should someone fall into a tank around the time agitation is taking place – the chance of rescue will be gone if you are overcome by hydrogen sulphide gas. Instead ring Emergency Services on 999 or 112.
Agitate for a minimum of 30 minutes and don’t enter the building for at least an hour after agitation.
Be careful – slurry gases can kill!