Hydrogen sulfide gas isn’t mundane

Manure safety might seem like a boring, overdone topic, but that isn’t the case when farmers continue to die in manure-related accidents. In many cases, death is due to hydrogen sulfide (H2S) buildup in and around manure storage, spreaders and other handling equipment.

Walter Grose has been working with liquid manure for 45 years. He shared what he’s learned about handling manure with safety in mind, with an emphasis on deadly H2S.

Following an accident in which three people were killed in a manure incident, Grose wanted to learn more about the timing of H2S buildup.

“It’s a silent gas. You can’t smell it, you can’t see it,” said Grose. “It sneaks up on you and all of a sudden you’re dead, lying beside the manure spreader.”

For his experiment, Grose positioned a three-gas monitor atop a manure spreader at the fill hole as the spreader was filling. There was a lot of carbon monoxide (465 ppm), but H2S measured 151 ppm. Oxygen was normal at 20.9%.

“It wasn’t a lack of oxygen,” Grose said, explaining the results of his study. “We had poisonous gas present at the top of the manure spreader. We spread the load of liquid manure, then I climbed to the top of the spreader and stuck the hose down inside. We took a sample of the manure that was in the bottom of the spreader.”

The H2S measured 70 ppm, which Grose said is still high, but the oxygen remained at 20.9%.

Next, Grose drained all the manure from the spreader. The H2S level was now at 25 ppm; oxygen was steady at 20.9%.

“The three-gas monitors are set to go off at 15 ppm” for H2S, Grose said. “That’s when it smells like rotten eggs. At 25 ppm, you need fresh air. If you are agitating a pit or get a whiff of manure after the monitor goes off, you should go home for eight hours of fresh air.”

Gas monitors vary in price but are worth every penny to prevent death. Grose described a simple H2S monitor as something that’s easily worn all day. Ideally, the monitor is placed on a belt or on the top of a rubber boot.

“The reason for that is to make sure the monitor is down low,” said Grose. “Hydrogen sulfide is a heavy gas, lower than oxygen, and it stays low.” A low monitor will pick up H2S quickly and allow time to safely leave the area.

A three-gas monitor can track levels of carbon monoxide, H2S and oxygen. “That’s how we can find out if there’s cross-contamination with methane,” said Grose.

He cautioned users to not allow the monitor to go down into the manure spreader because the sensors can become damaged. For better results, put a hose down into the spreader and monitor from there.

To ensure full and proper function, Grose bump tests gas monitors to confirm the sensors respond to target gases and that alarms function properly. He tests monitors prior to initial use at the beginning of the day, and again part way through the day. If the monitor has been out of the spreader, Grose bump tests again to be sure it’s still providing accurate readings.

Despite bump testing, Grose cautioned farmers that walking around a pit during agitation can be extremely hazardous.

“At 25 ppm you may start to not smell the rotten egg gas,” said Grose. “At 100 ppm, you will get a headache. As high as 300 to 1,000 is instant death. People say ‘Maybe you will just be knocked over,’ but who wants to take that risk? With hydrogen sulfide, you take one breath in, but you don’t get to breathe out. There isn’t a chance to say ‘This smells bad’ because your olfactory senses are burned on the first whiff and you can’t smell anything after that.

“When there’s an accident and someone is killed inside a manure spreader, it’s devastating,” said Grose. “It hurts the family, the farm and people don’t recover.”

One story that sticks with Grose is a beef farmer who said his cows were dropping dead as he was mixing manure. The farmer ran to the door but couldn’t get to it because the cows were crowded there. After a cow dropped dead in front of him, the farmer jumped over the cow, went outside and passed out. It took him a while to recover.

In another incident, a farmer crawled up the tank ladder and looked inside to see how full the spreader was. He passed out, fell back onto the ground behind the spreader, and when he woke up, the manure was up to his neck and only his head was exposed. Most of the pit had emptied and the farmer was in the liquid manure.

“Things we think are ‘easy,’ such as fixing a liquid manure spreader, need to have precautions and we need to think safety,” said Grose.

Last year, two men in New York passed away in a manure spreader. “The rubber hose jumped in the spreader and they thought they could go in after it to get the hose,” said Grose. “The problem was they had let the manure spreader sit over lunch. The sun was on the spreader and hydrogen sulfide started to build up. The first man went in, passed away, then the second man went in and passed away.”

An underground dry well reception pit proved to be a dangerous place to be. “The farm crew, construction crew and another group were doing maintenance,” Grose said, explaining the incident. “They were told by the foreman to not enter the manure reception area because it was dangerous. But they were ‘just going down to change a hose.’ People don’t see that even though it’s a dry well, they don’t realize there could be hazardous gas, but as soon as they take the hose apart, the gas comes back up into it. There were two people from each of three companies involved in the incident, and all six passed away. They were family members, most from one family.”

In many cases, farmers who had serious accidents or death were bedding with gypsum, which increases H2S levels. Grose warned farmers who bed with gypsum to be extra cautious and pay close attention to H2S levels.

Any of these incidents could happen to you, a family member or a worker on your farm. Manure safety is a topic worth the time for education – and worth reviewing more than once during the season.

by Sally Colby