Common sense is not enough when it comes to creating a safe working environment on farms.

March 12 2024 07:20 AM

Manure emits four dangerous gases that can be deadly at certain concentrations.

More than 170,000 agricultural workers around the world are fatally injured every year, and between 60,000 and 70,000 of those injuries occur in the U.S.

Safety may at times take a backseat to other priorities on a dairy, but Charles Gould of Michigan State University (MSU) Extension believes it should be at the forefront — daily.

Gould’s conversation with MSU Extension educator Martin Mangual on an episode of the podcast Virtual Coffee Break addressed potential dangers of agricultural work and ways in which farmers and their employees may mitigate risk.

One of the greatest threats to farm safety is manure storage, said Gould. Manure emits four deadly gases: hydrogen sulfide, methane, ammonia, and carbon dioxide. Each of these, at varying concentrations, can cause serious health problems, so knowing what to look for is essential in order to provide a safe work environment.

Hydrogen sulfide

Hydrogen sulfide numbs sensory nerves in the nose, making it particularly difficult to detect. With exposure to between 10 and 100 parts per million (ppm), more noticeable symptoms begin to occur, including eye and throat irritation, vomiting, nausea, and diarrhea. At over 600 ppm, Gould said, exposure to the gas is fatal.

■ Methane

Methane displaces oxygen and can cause explosive reactions at fairly low concentrations. Make sure there is no open flame near the manure, Gould said, and maintain a clear area around the pit.


Ammonia may be the easiest to detect. It is so pungent, Gould said, that a high concentration of the gas will cause people to vacate the area, regardless of other symptoms.

Carbon dioxide

Exposure to carbon dioxide at a level of between 40,000 and 60,000 ppm for 30 minutes will cause drowsiness, heavy breathing, and headaches. At 250,000 ppm or greater, exposure to carbon dioxide is fatal.

Know the signs

If it isn’t under ventilating slats, Gould said a manure pit should be fenced in with proper warning signage.

“Monitor gas levels regularly,” he added. “Just because you’re outside, it doesn’t mean that you’re safe.”

Gould and Mangual also emphasized how critical it is for farmers and employees to understand the signs of exposure and to have emergency protocols in place. For instance, an untrained employee might attribute irritated eyes to a recent hay harvest rather than to an overexposure to hydrogen sulfide. If they understand the warning signs, they will better know what is happening and how to remove themselves and others from the premises.

They further advised maintaining a buddy system, keeping breathing apparatus equipment near the site, and setting up lines of communication across the property. If someone begins to show signs of overexposure, do not approach them or the area. Instead, call 911. The last thing you want is a second or third fatality.

Take action

Gould’s final piece of advice? “Do not rely on common sense,” he stated.

On a farm, you can’t control what kind of exposure you may encounter on any given day, but you can control how well you prepare yourself and your team for dangerous situations. Having protocols and procedures in place is the surest way to promote a safe work environment.

Consider taking advantage of MSU Extension’s resources as well. Their Manure Hauler Certification Program includes a video about farm safety, and their feed program evaluations for individual farms offer risk assessments and best practice recommendations. These resources can be found at

This article appeared in the February 2024 issue of Journal of Nutrient Management on page 22. Not a subscriber? Click to get the print magazine.