By Erica Rogers

Harvest season is upon us. With that in mind, many farms will be spreading manure, and pits will be agitated and emptied. Be alert of your surroundings when working around manure storages, as manure gases can quickly become overpowering.

In June 2015, a father and son from Cylinder, Iowa, were both killed from manure pit gas at their Iowa hog facility. During a routine pumping of manure from one of the hog facility pits, the son climbed down into the pit after dropping a piece of equipment and was immediately overcome by the manure gas. His father went in after him and experienced the manure gas as well.

Similarly, in 2016, a Wisconsin farmer was agitating manure in an outdoor lagoon before spreading on fields and was also overcome by manure gas.

These stories serve as a reminder of knowing which manure gas to be aware of and how to respond in emergency situations.

Gases of concern
Four gases of major importance are ammonia (NH₃), carbon dioxide (CO₂), methane (CH₄) and hydrogen sulfide (H₂S). These gases are produced by microbial activity within the manure from the microbial respiration that occurs (rather than use oxygen for respiration, bacteria use inorganic sources like nitrogen and sulfur).

• Ammonia. With its sharp, pungent smell, NH₃ in high concentrations can cause eye ulcerations and severe respiratory aggravation. While NH₃ is typically not deadly, it is important to consider long-term exposure effects on respiratory health on those that are in proximity with it on a day-to-day basis.

Just as humans can suffer respiratory effects from inhaling NH₃, other livestock are susceptible as well. In swine, at only 50 ppm, there is an expected decrease in performance and health. Additionally, long-term exposure at over 300 ppm will cause convulsions.

• Carbon dioxide. Carbon dioxide may not appear to pose a threat like some of the other manure gases; however, it is dangerous from the perspective that it can replace the oxygen in your blood. Moderate concentrations of CO₂ can lead to shortness of breath and dizziness.

As this is a byproduct of livestock respiration, animals in confined spaces can also be affected by asphyxiation from CO₂. An Extension article by Donham et al. (2010) notes that humans can tolerate up over 260,000 ppm before death, while swine can only tolerate up to 200,000 ppm.  

• Methane. Highly flammable, CH₄ is not a concern from a human respiratory standpoint. If a building with manure storage is not ventilated properly, it can cause headaches and asphyxiation. Additionally, CH₄ tends to build up in the foam that accumulates on the top of liquid manure and is highly flammable. The explosive potential of CH₄ is dangerous to both people and livestock within proximity of this gas.

• Hydrogen sulfide. Acutely dangerous, H₂S is the gas most often associated with manure-related deaths on farms and is considered to be the most acutely dangerous, according to the National Ag Safety Database. This gas travels readily along the ground and in confined spaces, like manure storages. It causes paralysis of the nerve cells in the nose, which deadens the smell at only 100 to 150 ppm. At 700 to 1,000 ppm, rapid loss of consciousness and death can occur in minutes.

Even if someone is exposed to high concentrations of H₂S for only a short amount of time, the reaction to the gas can be delayed up to 24 hours and can include pulmonary edema (fluid buildup in the lungs), possibly leading to death. Similarly, other long-term neurological effects from H₂S exposure are possible.

Like its counterpart gases, H₂S is also a danger to livestock, specifically swine, in that it only takes about 20 ppm to start seeing signs of nervousness, fear of light and loss of appetite. When concentrations reach 200 ppm, swine may experience pulmonary edema and death shortly thereafter.

Warning signs
While several signs of being overcome by manure gases have been mentioned, there are others to be on the lookout for as well. Some of these include feeling hot and clammy, loss of motor skills, irregular or fast heartbeat, tightness of chest, panting, nausea and vomiting, and anxiety.

Several different types of manure gas monitors can be used on the farm. The monitor used depends on the farm, as well as the location of the manure storage, and whether it is a confined or unconfined space. Consider the type of gas you may come into contact with, as well as the price that works in your budget.

Follow manufacturer recommendations of equipment when agitating and handling manure in an enclosed pit:

• Ensure proper ventilation, and fans are on and working.

• When working around or near a manure pit, let someone know where you are and what time you are going. This lets a person know right where to look if you are not back in a timely manner.

• If someone you know or even an animal or pet is overcome by manure gas, do not go in after them unless you have proper respiratory protection.

• Should you encounter a situation where someone goes down and is unconscious, immediately call 911, as first responders have the proper respiratory equipment and training to enter these dangerous situations.

• If it is available, wear a gas monitor or have one in the manure storage to detect manure gas concentrations that may be approaching dangerous, life-threatening levels.

• When manure is being agitated, be aware of your positioning to the pit and where the manure gases are likely to settle.

• Be cognizant of manure tankers and how easily manure gases can settle inside this type of small and confined space.

• Gases tend to settle inside tankers, as well as leak out the top, which can pose a threat to those who examine and clean the tankers.

• Wear personal protective equipment, such as a proper fitting respiratory mask, if you go into a confined manure storage.

By understanding the dangerous gases found in manure, knowing the warning signs of a person who is experiencing high concentrations of manure gases and implementing safe practices when working around manure, there is the potential for fewer accidents and deaths. Who knows, you just may save a life, maybe even your own. 

Rogers is an environmental Extension educator with Michigan State University Extension in Gratiot County.