Manure Storage and Handling


Hydrogen Sulfide Health Effects Non-Enclosed Manure Storage Safety Tips Safety Recommendations and Practices

Photo looking down into a manure reception pit
Photo looking down into a manure reception pit

The decomposition of manure that occurs in manure pits generates methane, hydrogen sulfide, carbon dioxide, and ammonia gases. These gases can produce oxygen-deficient, toxic and/or explosive atmospheres.

A person might enter a manure pit one time without apparent problems, but the next time could die. The most serious problems with gases occur when manure is agitated or when ventilation systems fail. However, gases are constantly being produced and there is never a “safe” time to enter a pit.

To reduce the danger of manure pit gases, take the following precautions:

  • Never enter a pit, especially during or just after agitation. Without testing for toxic gases, there is no way to know if it is safe.
  • If absolutely necessary to enter a pit, always wear a self-contained breathing equipment with oxygen supplying tanks. Cartridge respirators are not sufficient.
  • Always wear a safety line and work with at least two other people outside the pit.
  • Remove all people and all animals from buildings over pits before pit agitation.
  • Provide maximum ventilation when agitating or pumping manure.
  • Do not smoke or have any other fire or ignition source around manure pits.

Hydrogen Sulfide Health Effects

Hydrogen sulfide is a colorless, flammable, extremely hazardous gas with a “rotten egg” smell and it is produced by the break down of animal wastes or manure. It is heavier than air and can collect in low-lying and enclosed poorly ventilated areas such as reception pits, ditches, or manholes. In manure processing buildings it may collect in areas with low air movement, dry motor pits or walled off areas.


 Short Term Symptoms/Effects

  •  Typical background concentrations
  • Odor threshold (when rotten egg smell is first noticeable to some.)
  • Odor becomes more offensive at 3-5 ppm.
  • Prolonged exposure may cause nausea, tearing of eyes, headaches or loss of sleep.
  • Airway problems (bronchial constriction) in some asthma patients.
  • Above 30 ppm, odor described as sweet or sickeningly sweet.
  • Possible fatigue, loss of appetite, headache, irritability, poor memory, dizziness.
  • Slight conjunctivitis (eye irritation and redness).
  • Respiratory tract irritation after 1 hour.
  • May cause digestive upset or loss of appetite.

IDLH- Immediately Dangerous to Life and Health

  • Leave area and get to your safety zone.
  • Coughing, eye irritation, loss of sense of smell.
  • Altered breathing, drowsiness after 15-30 minutes.
  • Throat irritation after 1 hour.
  • Gradual increase in severity of symptoms over several hours.

Death may occur after 48 hours.

  • Marked conjunctivitis and respiratory tract irritation after 1 hour.
  • Pulmonary edema (fluid in lungs) may occur from prolonged exposure
  • Staggering, collapse in 5 minutes.
  • Serious damage to the eyes in 30 minutes.

Death after 30-60 minutes.

  • Rapid unconsciousness, “knockdown” or immediate collapse within 1 to 2 breaths.
  • Breathing stops.

Death within minutes.


Nearly instant death


What about long term health effects?

Some people who breathed in levels of hydrogen sulfide high enough to become unconscious continue to have headaches and poor attention span, memory, and motor function after waking up. Problems with the cardiovascular system have also been reported at exposures above permissible limits. People who have asthma may be more sensitive to hydrogen sulfide exposure. That is, they may have difficulty breathing at levels lower than people without asthma.

Source: OSHA. Accessed November 2, 2016.

Non-Enclosed Manure Storage Safety Tips

Non-enclosed manure storage should be assessed to determine employee exposure to safety and health hazards.

Printable PDF Version: Non-enclosed manure storage safety tips

Injuries and fatalities occur in confined space manure storages that are enclosed, such as beneath animal quarters; or below-ground reception and pump out pits; and in non-enclosed earthen, synthetic or concrete lined manure storages. Non-enclosed manure storages are open to the atmosphere but may meet the definition of a confined space in terms of occupational safety and health based on storage design and employee exposure to hazards.

In the case of non-enclosed manure storage, hazards may include:

One potential hazard is someone falling into the storage and being engulfed in the manure slurry.
  • A thick liquid and floating crust that make swimming, buoyancy, or even moving around very difficult.
  • Steep and slippery slopes that can make getting out of manure storage difficult or impossible.
  • An acceleration of hazardous gases (primarily methane, hydrogen sulfide, carbon dioxide, and ammonia) release from manure due to movement, agitation, removal, or addition of manure to storage.
  • Localized layers of hazardous gases existing above manure surfaces, especially on hot, humid days with little to no breeze.
  • Not having sufficient oxygen to breathe if a person is ‘treading’ in manure because of inability to get out.
  • A slow response time for adequate emergency actions because of site isolation and remoteness.
  • Potentially hazardous equipment in and around the manure storage.

    Color photo of a manure agitator in manure slurry.
    Agitation accelerates the release of hazardous gases. Employees should know the signs and symptoms of these gases.

Safety guidelines to follow:

  • Make sure everyone near manure storage structures understands the hazards that exist, including symptoms and effects that the various manure gases have on their health. Remember to include these gases in your Hazardous Communications Program.
  • Explosive gas may settle in pockets where agitation or pumping is occurring. No smoking, open flames or sparks should be allowed.
  • Make sure the non-enclosed manure storage has a fence installed around the perimeter and access gates are locked to keep unauthorized personnel from entering the area.
  • Post warning signs including manure drowning hazard signs and “Danger Manure Storage” or “Danger Keep Out,” or “Danger Keep Away,” on all sides of non-enclosed manure storage. If possible, these signs should be located by gates.
  • Keep bystanders and non-essential workers away from non-enclosed manure storage during or other accessible areas during when pump out operations are in progress.
  • Wear a safety harness with life-line attached to a safely located solid object or anchor at any times you enter the fenced in area of non-enclosed manure storage. If retrieval is needed, this equipment will improve the possibility of a successful rescue.
  • Never work alone. The second person’s role is to summon help in an emergency and assist with rescue without entering the manure storage.
  • Move slowly around unenclosed manure storages as the ground can sometimes be uneven and may cause a person to trip or stumble.
  • Understand equipment being used and have emergency shut-down procedures prepared.
  • If equipment malfunctions or maintenance is required during agitating or pumping of the manure, shut all equipment off and remove it from the manure storage before servicing or repairing.
  • If you feel unsure or uncomfortable with what you are getting ready to do near the manure storage; wait a moment and reconsider the action, contact a supervisor or farm manager, and review the situation before proceeding.
  • Be prepared to call 911 in case of an emergency. Being prepared includes providing specific directions to the site of the emergency, accurately describing the incident, and number of victims.

OSHA requires warning signs to be posted in English but a recommended safety practice is to post in additional language based on your workforce.

Adapted from: Open Air Manure Storage Safety Tips, Penn State University, June 2012. Authors: Dennis J. Murphy, Extension Safety Specialist, Agricultural and Biological Engineering; Robert Meinen, Senior Extension Associate, Animal Science Department, Davis E. Hill, Senior Extension Associate, Agricultural and Biological Engineering.

UW Madison, Biological Systems Engineering Contributors: Cheryl A Skjolaas, Agricultural Safety Specialist, UW CTR for Agricultural Safety and Health; David Kammel, Extension Agriculture Building Design Specialist; Brian Holmes, Extension Farmstead Engineering Specialist; and Rebecca Larson, Extension Bio-Waste Specialist

Photo Credits: Cheryl A. Skjolaas and Brian Holmes.

August, 2016

Safety Recommendations and Practices

Review of Practices and Recommendations for Wisconsin Livestock Farms

In November 2008, Manure Gas Safety – Review of Practices and Recommendations for Wisconsin Lifestock Farms was completed. The following is the Introduction from the report.

The death of five people from hydrogen sulfide inhalation on a Virginia dairy farm in July 2007 was a grim reminder of the hazards posed by gases associated with manure handling systems. The threat of accidents, combined with the increasing scale and complexity of manure management systems, prompted the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) and USDA, Natural Resources Conservation Service (NRCS) to convene an interagency team (members are listed in Appendix A) to review safety considerations related to certain manure handling practices. In particular, the safety review team focused on the expanding use of drive-in, covered storage tanks and transfer channels intended to be entered with machinery for removing sand bedding. This was identified as a potentially hazardous practice.

The team met from August 2007 to July 2008 to assess the safety aspects of this and other manure management practices and to provide recommendations to reduce the risk of accidents from manure management system gases. The group developed findings and reached recommendations through a consensus process that relied on the expert contributions from individual members and the review of research and industry findings and recommendations.

This report contains the findings and recommendations of the team. Chief among its findings, the team concluded that safety considerations currently incorporated into manure system designs and included in operation and maintenance plans have not kept pace with changes in manure management and the associated risks of manure gases. Safer system designs and management practices, along with increased awareness of these dangers, will be needed to help prevent manure gas tragedies from occurring on Wisconsin farms.

This report addresses the following areas:

  • Information and education
  • Revision to technical standards
  • Identification and notification to owners of unsafe systems
  • Adoption of safety measures and practices
  • Improved safety planning

A complete PDF of the report is available here.