Danger underestimated in manure pits

Photo from www.wisfarmer.com

Photo from www.wisfarmer.com

It’s a tragic tale that has become all too common.

A farm worker enters a manure pit to perform a simple maintenance task; probably one he’s done many times before. Only this time he is overcome by the deadly gases released during composition of manure. A co-worker or family member discovers them unconscious and tries to rescue them, only to become a victim themselves. Cause of death: methane asphyxiation.

In the wake of a string of deaths, the National Institute for Occupational Safety and Health (NIOSH) sent out a call, asking for assistance in preventing deaths of farm workers in manure pits.

Urgent need to educate

“An urgent need exists to inform farm owners and workers about the dangers of enter such pits, where oxygen-deficient, toxic and/or explosive atmospheres often result from fermentation of the wastes in confined areas,” according to the NIOSH website. “These hazards have been known for several years. However, recent NIOSH investigations conducted under the NIOSH Fatal Accident Circumstances and Epidemiology (FACE) Program suggest that farm workers are unaware of the danger, and many deaths continue to occur as a result of entry into manure pits.

The Occupational Safety and Health Administration defines an confined space as being large enough and so configured that a worker can enter and perform work; has limited or restricted means for entry or exit; and is not designed for continuous human occupancy.

“Even if you just put your head in there to take a peek, if any part of your body passes through an opening, that’s still considered an entry,” said Dan Neenan, director of The National Education Center for Agriculture Safety.

Toxic atmosphere

Inside the pit, the manure undergoes anaerobic digestive fermentation to form fertilizer. The digestive process can generate four potentially dangerous gases: methane, hydrogen sulfide, carbon dioxide and ammonia. The accumulation of these gases within the confined space of the manure pit can produce an oxygen-deficient, toxic environment.

Although OSHA defines an open-air, non-enclosed manure storage area still meets the definition of a confined space, people may be unaware of the danger of toxic gases adjacent to a confined space, Neenan said.

“A farmer was agitating his fenced off lagoon when his two little boys had been riding their bicycles nearby. He looked to see them on the ground, unconscious,” Neenan said.

The heavier gases displace oxygen around the confined space, causing a depletion of oxygen essential for life. Neenan said humans need at least 19.5 percent oxygen to be safe. Once oxygen levels begin decreasing, coordination is impaired, respiration increases, judgment is impaired, unconsciousness follows.


Dismal odds

If victims are moved outside within 4-5 minutes, recovery is still possible. However, after being in a state of oxygen depletion after 6 minutes, almost half of the victims will die.

“Once oxygen falls below 4 to 6 percent, the victim experiences a coma in 40 seconds followed by death,” Neenan said.

The culprit, Neenan said, is hydrogen sulfide gas, characterized by it’s “rotten egg” smell. This warning sign of the toxic gas’ presence is quickly erased as it paralyzes the sense of smell.

“You might think that if you can’t smell it, it must be getting safer to be in there,” Neenan said. “This gas can cause respiratory failure and death within minutes.”

Those entering a confined space should perform the following safety measures: mechanically ventilate the area at a rate of at least four volumes per hour; check the air quality and oxygen levels before entering; wear a chest or full body harness; wear an air supplying respirator; turn off all power and equipment to the pit except for fans; and use an attendant.

“When entering a pit, it’s a minimum two-person job. The attendant stands outside, making sure the person inside is ok,” Neenan said. “Sixty percent of the people that die are would-be rescuers. If that person goes down, it’s the attendant’s just to winch them out or call 911.”

Because many farm operations have facilities off of the main farm, Neenan says it’s important for workers to know the physical address of where the manure storage unit is located when summoning a rescue team or ambulance.

While larger farming operations are held to OSHA safety standards, small farming operations with less than 10 employees are exempt from enforcement guidelines.

Safety guidelines

Neenan encourages farmers to create and follow safety guidelines to keep themselves, family members and hired workers safe.

Those owning open-air manure storage systems should install a fence around the perimeter and keep access gates locked to keep unauthorized personnel from entering the area. Barriers or blocks should be placed near the opening to keep farm equipment from accidentally falling in to the lagoon.

Place “manure drowning hazard” signs near the open-air storage area. Also place “no trespassing” signs on all sides of the storage.

While tractor accidents account for the most fatalities on farms, manure pits are more lethal, claiming multiple victims at a time, often members of the same family.

Neenan said it’s critical to educate farm workers on the immediate danger posed by entry into manure pits.

“Agriculture is one of the most dangerous industries in the U.S.,” Neenan said. “You have a right to a safe and healthful work place and need to know the dangers and risks involved.”

Recommended: ConSpace Case Study and PHX Con Space

Realistic Hands-on Gas Monitor Training by HazSim

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