Animal manure pits are often necessary around livestock. Manure storage poses a hazard to agricultural workers due to the danger of toxic gas build up, drowning, or engulfment. Workers need to be aware of these hazards and use safe work practices such as controlled access, respiratory protection, and confined space entry procedures when working around them.
Manure can be stored in above-ground tanks and vats or below ground in pits or ponds. Manure pits can be covered with closed or slotted flooring and used below livestock in buildings or pens.
The first level of safety around manure pits is to control unauthorized access by installing fences and locks on pit doors and covers. Good security can prevent someone walking into a pit by accident. Because liquid manure can dry on top, the surface may appear safe to walk on. Place warning signs about the unstable walking surface to prevent drowning and engulfment.
Through decomposition, manure creates gases such as hydrogen sulfide, carbon dioxide, ammonia, and methane. These gases are hazardous because they are toxic in high concentrations, can displace oxygen, or, in the case of methane, are flammable. Open pits and containers of manure are more exposed to the air and less likely to create high levels of gases. Covered pits and tanks of manure, along with manure pits within buildings, pose the greatest hazard of gas buildup. Regardless of the storage type, when manure is disturbed through agitation or pumping, the risk of gas release is the highest.
As a safe work practice, remove all unnecessary personnel from around a manure pit before agitation or pumping. Maximize ventilation in the area through fans and blowers. Be cautious not to place the equipment too close to the manure, an electric spark or open flame could ignite flammable methane gas and cause an explosion. Start the agitation slowly in order to control potential gas release. Never enter a manure pit during or immediately after agitation or pumping.
When you must enter a manure pit, note that many accidents and deaths occur when people become overwhelmed by the gas buildup. These tragedies are sometimes made worse when family or coworkers enter the pit to perform a rescue and are overcome themselves. Minimize your need to enter manure pits. Install pumps and other equipment in easily accessible areas so that you do not need to enter too far into the pit. Ventilate the area as much as possible before entry.
Get the training and testing required and wear an air-supplying respirator to ensure a supply of good breathing air before you enter a manure pit. Use confined space entry procedures by wearing a harness and lifeline. Make sure there are at least two people equipped with their own harnesses, lifelines, and air-supplying respirators outside the pit ready to rescue you if necessary.
Remember, safety is it, when you’re in the pit.