A liquid manure system produces 4 gases which are potentially hazardous to workers and animals. The decomposing manure slowly releases these gases into the liquid and the surrounding atmosphere. During agitation of the manure large quantities of gas are released into the air. Tragic human deaths and animal losses have occurred during agitation or from humans entering the pit areas.
Piercy, Larry R. and Taraba, Joseph L., "Safety Precautions with Liquid Manure Storage Systems: Warning--Manure Gases Can Be Dangerous" (1982). Agricultural Engineering Extension Updates. 74.