By Dr. Stephanie Ostrowski, DVM, MPVM, DACVPM

Farm life is full of hazards, most of them well-recognized, but some invisible—you can’t see them coming. The potential for asphyxiation from heavier-than-air toxic manure pit gases, for example, has long been recognized. A case in point: A farmer and 16 of his cattle died last summer in a freak accident after a “deadly dome of air” formed in a Wisconsin farm’s manure holding tank.

Amherst, Wisc., farmer Michael Biadasz, 29, succumbed to gas poisoning on his family’s farm while agitating waste in the farm’s outdoor manure pit. He was  overcome by either methane or sulfur oxide fumes, which also poisoned 16 cattle. Bob Biadasz, Michael’s father and co-owner of Biadasz Farms, said the tragedy was the result of a “perfect storm” of unusual and unexpected weather conditions. When the tank was prepped to be pumped, warm upper air temperatures trapped the gases in a dome of air, poisoning Michael and the cattle. The morning was calm, and a heavy fog stayed close to the ground. The invisible fumes from the pit also hugged the ground.

The four main gases produced from decomposing manure are hydrogen sulfide, methane, ammonia, and carbon dioxide. In high concentrations, each of these gases may pose a health threat to humans and livestock (see Table 1 in link to reference). In swine housing facilities, where the manure pit is often located below the facility floor, these gases are generally detectable in low concentrations throughout the year. When pits are agitated for pumping, some or all of these gases are rapidly released from the manure and may reach toxic levels or displace oxygen, increasing the risk to nearby humans and livestock. (Doss et al.)

Methane, carbon dioxide, and carbon monoxide are all odorless gases. Methane is potentially explosive at concentrations > 50,000 parts per million (ppm), and causes rapid asphyxiation at 500,000 ppm. Carbon monoxide is odorless and acts by preventing oxygen from being transported by the hemoglobin in our blood. Concentrations > 50 ppm cause headaches, fatigue, nausea, and impaired mental ability; prolonged exposure to 1000 ppm can cause convulsions and coma, and concentrations > 4000 ppm can rapidly result in death.

Hydrogen sulfide is considered the most dangerous gas in farm manure pits. The gas is highly toxic and is rapidly released from decomposing manure during agitation and pumping. It is highly irritating to eyes and lungs, so low concentrations may serve as a warning and cause people to leave the dangerous area. High concentrations of hydrogen sulfide, however, paralyze the nerve cells of the nose to the point that a person can no longer smell the gas. Thus, workers may be quickly overcome by hydrogen sulfide anytime they are working around a pit, whether they are climbing down a ladder to make repairs or leaning down to take a manure sample.

Because it is heavier than air, hydrogen sulfide accumulates above the liquid level of the pit. Concentrations of hydrogen sulfide can rise from 5 parts per million (ppm) to more than 500 ppm in just seconds after agitation begins. Concentrations > 600 ppm are rapidly fatal and can kill an individual after taking only one or two breaths. The person collapses immediately, apparently unconscious, and dies without moving again.

A victim can be safely evacuated only if the rescuer is wearing a self-contained breathing apparatus (SCBA). Generally, a rescuer has about six minutes to begin cardiopulmonary resuscitation (CPR) before brain damage/death occurs. Unless the rescuer is wearing SCBA protective equipment (see section on personal protective equipment), there is a strong likelihood the rescuer will also succumb to the toxic gases.

Numerous tragedies have been recorded involving  several farmers who have been killed while attempting to rescue someone from a pit or facility. Since the accident, the Biadasz family has been honored for their efforts in promoting farm safety. READ MORE