Manure Gas Info Sheet
Manure gases are some of the most common toxic gases in a farm environment.
Here are the answers to some of the most commonly asked questions about these gases.
What is manure gas?
- Manure gas is actually a name used for several different gases formed by the decomposition of manure.
- Four gases of concern are hydrogen sulfide, ammonia, methane, and carbon dioxide. In certain concentrations, all of these gases are toxic to animals and humans.
- The gases of most concern are hydrogen sulfide and ammonia. Hydrogen sulfide is the most toxic manure gas.
Why are manure gases deadly?
- In the right conditions, manure gases can displace the oxygen in an area so that a person entering that area is suffocated (i.e., asphyxiated), leading to death.
- High concentrations of hydrogen sulfide can cause sudden loss of consciousness without warning.
- The gases can lead to other toxic effects that make a person extremely ill and cause long term health problems.
When and where are manure gases present?
- Always assume that manure gases are present in manure storage area and take the proper precautions.
- Manure gas levels are generally very high when manure is agitated or when ventilating systems aren’t in place or working properly.
- On hot, humid days when there isn’t much wind, even a relatively empty manure pit can contain high concentrations of toxic gases and/or a lack of oxygen.
- Hydrogen sulfide and carbon dioxide are heavier than air, so they tend to settle in low areas of manure storage or accumulation.
- Ammonia and methane are lighter than air, so they are usually found above and around manure storage areas.
What are some tips to avoid exposure to manure gases?
- Remove all people and, if possible, all animals from building over manure storage areas before pit agitation.
- Provide maximum ventilation when agitating or pumping manure.
- Do not smoke or have other ignition sources present around manure pits.
- Do not fill manure pits to capacity. Leave 1-2 feet of air space.
What are some manure gas safety tips?
- Never enter a manure pit without proper training and equipment (see below).
- Remove all people and, if possible, all animals from building over manure storage areas before pit agitation.
- Provide maximum ventilation when agitating or pumping manure.
- Do not smoke or have other ignition sources present around manure pits.
- Do not fill manure pits to capacity. Leave 1-2 feet of air space.
What if a manure pit needs to be entered?
- Never enter a manure pit unless you have specialized training and equipment. Disposable dust respirators (i.e., dust masks) and chemical cartridges are not adequate protection to safely enter a manure storage area if the concentration of hydrogen sulfide and oxygen levels are not known.
- If you don’t have specific training in confined space entry, get the help of your local fire department or emergency services before anyone enters the manure storage area. These individuals will be properly trained to use a self-contained breathing apparatus (SCBA). They will know how to use a safety line and harness with retrieval equipment and will work with two other people outside the pit to ensure a safe entry.
- This advice is critical if you are ever faced with an emergency where someone has been overcome by manure gases. Do not attempt the rescue yourself. The manure gases that caused them to lose consciousness are still present and could harm you, too! There are too many tragic stories of multiple deaths involving manure gases because a family member, neighbor, or coworker attempted to rescue someone who lost consciousness in a confined space. If you are faced with this situation, call 9-1-1, tell the dispatcher about the victim, and do not attempt the rescue yourself. Your local rescue squad will arrive to assist with rescuing the manure gas victim.
- No one should enter a manure pit or lagoon without a SCBA or without first inspecting the gas levels with a reusable continuous-reading electronic gas monitor or a detector tube attached to an air pump to check hydrogen sulfide levels. Contact your extension safety specialist, an environmental testing firm, or the National Farm Medicine Center for recommendations on specific equipment and costs.
Resources:
- This webpage was adapted from: https://www.marshfieldresearch.org/Media/Default/NFMC/PDFs/ManureGas.1.pdf.
- The National Farm Medicine Center is Four Gas Monitor Program (for fire departments): https://rfdash.org/ag-rescue-training/four-gas-monitor-program/.
- On August 15th, 2016, Mike Biadasz was agitating a large outdoor manure pit on the family farm when he was fatally overcome by hydrogen sulfide gas. His family hopes that his story will raise awareness about the dangers of manure gas: https://tellingthestoryproject.org/mike/.
References:
- Donham KJ and Thelin A. Agricultural medicine: occupational and environmental health for the health professions. Ames: Blackwell Publishing, 2006.
- Doss HJ, Person HL, and McLeod W. “Beware of manure pit hazards.” NASD. April 2002. National Ag Safety Database. 10 August 2009. https://nasdonline.org/1292/d001097/beware-of-manure-pit-hazards.html.