Iowa State University Extension agricultural engineers say these episodes highlight the caution needed when agitating and pumping manure from pits beneath buildings.

Liquid manure in pits undergoes slow decomposition which creates several gases including methane and hydrogen sulfide, both of which can create dangerous situations. The rate of gas release from the manure can be drastically increased when the manure is agitated (stirred) during pumping. This increase is especially true for hydrogen sulfide, which can have a lethal paralysing effect.

In addition to the concern about gas release from pumping and agitation is the concern about rapid gas release in pits with excessive foam. It is believed that pits with substantial foam prevent the normal release of methane from the deep-pit facilities. Captured methane can be released quickly during agitation or when other activities such as power-washing occur, that can rapidly break the foam. The rapid release of methane mixing with fresh air causes methane to reach the explosive limit for methane. If this mixture comes into contact with an ignition source, it can cause a flash fire or explosion.

To minimise risk of injuries and flash fires, manure handlers should follow these steps:

• Review your emergency action plan with all workers and have emergency contact numbers available at the site.
• Prior to agitation or pumping, turn off electrical power to any non-ventilation equipment such as lights and feed motors, and extinguish any pilot lights or other ignition sources. Fully open all ventilation curtains or ventilation pivot-doors, but leave walk-in doors locked to prevent human entry.
• Run ventilation fans at maximum speed.
• Ensure that all people are out of the building and clearly tag all doors noting that the building is unsafe for entry during agitation and pumping.
• Do not agitate manure until manure has been pumped and level is at least two feet below the slats.
• When agitating the manure keep the jet of pressurised manure below the liquid surface. Don’t let the jet of manure strike walls or columns in the pit.
• Stop agitation when the manure level does not allow agitation below the liquid surface.
• Continue maximum ventilation for 30 minutes to an hour after pumping has ended before re-entering the building.
• NEVER enter a building or manure storage structure when liquid manure is being agitated or pumped.

The Iowa Pork Producers Association has door hang tags available to Iowa pork producers and commercial manure applicators that read “STOP Manure Agitation and Pump–Out in Progress.“