Manure and the potentially dangerous gasses from manure storage and agitation are one of the inevitable aspects of livestock farming. The combination of working in confined space and a farmer who needs to keep moving can be lethal.
Rob Meinen, Penn State extension in the ag safety program, describes confined space as ‘large enough to enter but with limited or restricted means of entry and exit, and not designed for normal, continual occupancy by a worker.’
“They’re easy to get in, but hard to get out of,” said Meinen, describing confined spaces. “OSHA would regulate these, but we don’t see much regulation of these in ag. Confined spaces should be regarded as a dangerous place, and anyone working on a farm and drops a wrench in there ought to find a better way to retrieve it other than enter that space. Always assume that confined spaces contain gasses. If you’ve been down in a sump area 20 times to unclog a pump, the 21st time is when you might run into danger. In a lot of cases, it’s the rescuer who dies.”
Meinen reports one study of swine manure showed the presence of 230 gaseous compounds. “Some gasses of concern include hydrogen sulfide, ammonia, methane and carbon dioxide,” he said. “Also of concern is the lack of oxygen — any gasses that displace oxygen can cause trouble.”
Manure gasses are the result of natural biological processes. “They’re an invisible danger,” said Meinen. “Some are odorless, most are colorless and some are explosive. Some sink and some rise. Methane rises; hydrogen sulfide sinks.
There are times of year when the microbes are more productive and producing more gas. The gasses we’re concerned about are the byproducts of microbial respiration. Degradation of manure results in the release of gasses.”
Hydrogen sulfide, which seems to be more predominant in manure that contains gypsum bedding, is particularly worrisome. Hydrogen sulfide can be detected by most people at a very low level — under 1 ppm. However, a worker’s sense of smell can be deadened after even short-time exposure, and he will be unable to smell it even at higher levels. “At 20 minutes of exposure at 10 ppm, we can experience eye irritation,” said Meinen. “At 50 to 100 ppm, we can become irritated by the smell — it’s very offensive. At 500 ppm we can become unconscious, and at 600 ppm, there’s rapid asphyxiation and possibly death.”
Meinen says one trait of hydrogen sulfide gas is that it will ‘hug’ or become stratified within the atmosphere above the manure storage or within a confined space. “You might be okay when you’re standing,” he said, “but when you bend over, you might be in trouble.”
While manure gas accidents can occur at any time of year, Meinen says most accidents occur May through August when the warmer weather causes greater microbial activity and more gas production. “One out of four incidents occurs in August,” he said. “That makes sense. We empty manure storage in spring and start into the crop year, then accumulate manure through summer. When silage comes off we start to apply again. But we aren’t out of the clear over winter — gas accidents can occur any time of year.”
Meinen encourages farmers to pay attention to body alarms and to take immediate action when experiencing dizziness, wobbly knees, feeling hot or clammy, lack of attention to detail, loss of motor skills, fatigue, anxiety. These can all be attributed to gas exposure. “This is one area where the work ethic of farmers can backfire,” he said. “We want to work and we work til the end of the job or the end of the day, but if you notice any of these signs, back off the work ethic and move out.”
Other signs, which may occur immediately or with prolonged exposure include severe eye irritation, decreased vision, irregular or rapid heartbeat, nausea or vomiting, shortness of breath without exertion, respiratory tract irritation, tight chest or loss of consciousness. “This seems obvious,” said Meinen, “but I’ve talked to at least four people who have woken up either in a barn or next to a manure tank and realized that they had succumbed to gas for a short period.”
Manure haulers and farmers who work in or around manure storage facilities can take some steps to remain safe when manure gasses are inevitable. First, invest in a monitor or metering device that measures gas levels. Operators who remain inside a closed tractor cab and operate the agitator from the cab are usually fairly safe, but there’s no guarantee that he’s safe from gas exposure.
“Observe agitation from a distance,” said Meinen. “The first hour of agitation is the worst, but never let your guard down. We know from previous work that hydrogen sulfide can come out in a ‘burst’. It’s a heavy gas, so higher is better.”
Meinen says most important point to remember is that farm owners and managers have a responsibility to design, supply, buy, operate and maintain manure storages and handling systems that are safe for workers, visitors and children “Kids are often the first ones to walk up and get too close and don’t understand the dangers,” he said. “We have to teach them and provide barriers to keep them safe.”