Hydrogen Sulphide in Swine Barns


Hydrogen Sulphide (H2S) awareness for liquid manure handling systems is needed to ensure worker and swine safety. Hydrogen Sulphide is created from decomposing biological material in the absence of oxygen. Sulfur enters the liquid manure system through feces and urine. H2S remains bound to manure molecules resulting in accumulation over time. The concentration of accumulated H2S can increase rapidly during agitation.

Properties of H2S

H2S is a colourless gas which smells like rotten eggs at low concentrations. Its density is slightly higher than air, and thus it may flow or settle into low-lying areas such as manure pits, shallow gutters, etc. The atmospheric conditions can also impact the level of H2S, with there being increased risk when the temperature is high. Because it does not bubble off like most other gasses and sticks to manure particles, it is not released in large quantities until it is agitated.

Hazardous Locations

There are several H2S hazardous locations in swine operations including:

  1. Shallow barn gutters
  2. In-barn deep manure pits
  3. Underground or outside storage tanks, lift or pump stations
  4. Earthen manure storage facilities
  5. Spreader tanks

Outdoor liquid manure holding facility.

Figure 1. Outdoor liquid manure holding facility.

Health Implications

H2S is the most dangerous gas produced from decomposing manure, and many people have died from H2S exposure over the years.

H2S enters the body through the lungs and dissolves in blood which is then carried throughout the body. There are several symptoms of H2S exposure for swine and people. Symptoms will vary with the concentration and length of exposure. At low concentrations H2S has a characteristic rotten egg smell, but at higher concentrations it paralyzes the sense of smell and is not detectable by the human nose.

At high levels, H2S will affect breathing by causing the respiratory control centre in the brain to shut down. Death occurs as the oxygen in the blood is quickly used up, causing the heart to stop.

Prolonged exposure at fairly low levels will cause eye, nose, mouth and throat irritation. This may be followed by giddiness, nervousness, depression, loss of appetite and/or energy. Fluid in the lungs and pneumonia may also occur. Long-term (chronic) exposure to low levels of H2S can cause fatigue, headaches, dizziness and irritability.

If you or a worker experiences any of these symptoms after exposure to H2S, exit the area and seek medical attention. Anyone knocked down by H2S must be treated by a medical professional immediately.

Impact of H2S on Swine

H2S exposure will also impact your pigs. Levels of 100 ppm can cause severe distress, eye irritation and drooling. Concentrations of 250 ppm cause cyanosis, convulsions and death.

Exposure Limits for Hydrogen Sulphide

Ontario’s Ontario’s occupational health and safety regulations have exposure level limits for H2S. The time weighted average for 8 hour exposure, 40 hours per week must not exceed 10 ppm. Short-term exposure limit for 15 minute exposure must not exceed 15 ppm. Immediate danger for life and health must not exceed 100 ppm.

The use of a personal H2S monitor is highly recommended when pulling pits and power washing (or any other time that manure agitation may be occurring). These monitors act as a warning device when H2S levels rise. If the alarm sounds proceed to a safe area immediately. If needed, seek medical attention. Personal H2S monitors can be purchased from most industrial safety stores.


Appropriate Appropriate manure pit management can assist in reducing the risk of H2S in your swine operation. Standard operating procedures and emergency plans for manure handling need to be created for the entire facility to ensure everyone’s safety.

Safety tips for pulling pits include:

  • Train workers in H2S awareness, the risks and dangers associated with agitating manure.
  • Familiarize workers with your standard operating procedures related to manure handling.
  • Wear an H2S monitor.
  • Use good communication with all workers.
  • Use a buddy system if possible when pulling pits. If not possible, have a communication system between the person pulling a pit and a co-worker.
  • Post signage in areas or on the doors where pit pulling is going to take place.
  • Maintain adequate ventilation (fans on full speed).
  • Ensure no co-workers are present in the location where pits are going to be pulled.
  • Remove animals from room if possible.
  • Remove yourself from the room once pit pulling starts.
  • Allow at least a foot between the slats and manure level. Pigs lying on slats can be overcome by accumulating gasses as they are lower to the ground.
  • Have and maintain a regular pit pulling schedule. Pull pits frequently to help reduce accumulation of H2S.
  • Never bend over into the pit.

For additional examples of safety precautions to include in a standard operating procedure for your farm visit “Pit Foaming and Manure Gasses” on the OMAFRA Livestock website.

Under no circumstances should anyone enter a manure pit, tank, lift or pump station without proper training and equipment when required. If a worker is knocked down by H2S, do not enter the room to rescue them without proper equipment such as a self-contained breathing apparatus (SCBA). H2S associated deaths often occur in pairs because a co-workers tries to rescue the knocked down individual and quickly is overcome with H2S themselves.


Hydrogen Sulphide (H2S) awareness for liquid manure handling systems is needed to increase worker and swine safety. H2S can be found in numerous locations throughout a swine operation. Standard operating procedures and emergency plans need to be implemented in every swine operation to enhance safety. The best management practices will aid in reducing the risk of H2S accumulation in swine facilities.


LaRoche., S. Hydrogen sulphide awareness for liquid manure handling systems. Prairie Swine Centre. 2009.

Ontario’s Occupational Health and Safety Act.

For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca