Photo by OSU CFAES.

The dangers of farm gases

By Dee Jepsen, Haley Zynda, Jason Hartschuh

Agriculture is the third most hazardous industry in the U.S. While many hazards are apparent, agricultural gases are considered silent dangers. Oftentimes they go unnoticed. Yet in the right atmospheric conditions they have potential to do great harm.

Working in and around confined spaces are a necessity on grain and livestock operations. There are four factors to know when it comes to agricultural confined spaces: recognition, respect, entry and rescue techniques.  


Being able to recognize a confined space is a critical first step. Confined spaces are defined as areas large enough for a person to enter and perform work but have a limited or restricted means for entry or exit. These spaces have unfavorable ventilation and often contain or produce dangerous air contaminants.

Farm structures that meet the confined space definition include grain bins, upright silos, manure pits, wells, sewers and parlor waste holding pits. Other areas on the farm that can accumulate gases, even without the presence of an enclosed structure, include manure lagoons, bunker silos and freshly filled silage storage bags.

Respect for the hazards

Agricultural gases pose a particularly difficult hazard because they are invisible. We as humans have a hard time responding to dangers we cannot see or touch. If you were to map the gases in a confined space, you would see they appear in layers. Gases stratify based on weight compared to atmospheric air. Heavier gases sink to the bottom, while those lighter than atmospheric air float to the top. A non-farm example of gas stratification is a helium filled balloon floating in atmospheric air; the gas inside the balloon is lighter than air, making it rise through the atmosphere.  

Hydrogen sulfide, carbon monoxide, carbon dioxide, and nitrogen dioxide are gases of interest that can cause negative health impacts. Hydrogen sulfide and nitrogen dioxide stratify near the bottom of the air space. Carbon dioxide and monoxide are roughly the same density as atmospheric air and mingle in the middle of a structure. Methane is the lightest of these gases and is found at the top of a structure. Regardless of their stratification, all have maximum concentration thresholds where they cause respiratory distress and can cause death within minutes if present in great enough concentration. 

Entering an upright silo or manure storage area

While atmospheric gases are invisible, they are always present. What is unknown, is the exact concentration of these elements. Therefore, the following management strategies should be practiced every time a person works in or around a confined space.

• Turn off — and lock out — all electrical equipment that is in the space. 

• Use an electronic monitor (with probe) to test the atmosphere before entering. 

• Turn on ventilation systems or add a fan to the area being entered.

• Wear a harness and lifeline to enter the space.

• Have an observer present to monitor the person in the space. 

• Have a rescue plan established if an emergency occurs.


It is important for “first on the scene” and first responders to understand the dangers of farm gases. It is not uncommon that firefighters are unfamiliar with agricultural facilities, machinery and livestock. Responders may be skilled in extrication and rescue, however they may not know the agricultural dangers that exist on a farm. By having a conversation with your local department prior to an emergency helps establish a response plan for the farm operators and the responders. 

Farm managers can invite their local fire departments to tour the property. While on the farm, the farmers and firemen can work together to identify hazards, not just for confined space emergencies, but also identify chemical storage areas and locate potential water sources for fire emergencies. This is a great time to discuss special equipment that may be needed for rescues on the property, like grain rescue tubes and gas monitoring equipment. It is also a time to ask if gas detection equipment is available for use when farm repairs are needed in a confined space. 

By recognizing confined spaces gases as potential hazards, farm workers and first responders can respect the dangers created by these invisible gases.

Dee Jepsen, Professor, can be reached at 614-292-6008 or  

 Haley Zynda, Extension Educator in Wayne county and may be reached at 330-264-8722 or Jason Hartschuh Extension Educator in Crawford County, can be reached at 419-562-8731 or This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research & Development Center, and the College of Food, Agricultural and Environmental Sciences.

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