Manure Gases

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Apr 1, 2003

"In August 2000, three men died on a Wellington County dairy farm following entry into a liquid manure tanker. The first victim was attempting to make repairs. The other two men were overcome when they tried to rescue him. All three victims suffocated due to the concentration of hydrogen sulfide within the tanker. A Coroner’s Inquest into these deaths was held in Drayton last fall." (Farmsafe Volume 27 Number 2 Spring 2002)

Every year farmers and farm workers without much forethought enter enclosed spaces and risk becoming killed or injured. The example above is one of many unfortunate accidents that happen around the country each year. In the above case this accident happened about 3 miles from the farm I grew up on and occurred on one of the regions largest farms.

Manure produces a wide variety of gases that can affect a person. These gases are particularly dangerous when they are contained within a confined space, barn or storage facility or while agitated for removal or spreading. They can rapidly overwhelm someone by causing respiratory irritation or asphyxiation. The most commonly referred to gases produced by manure are Hydrogen Sulphide (H2S), Carbon Dioxide (CO2), Ammonia (NH3), and Methane (CH4).

Hydrogen Sulphide is an extremely dangerous manure gas that is an asphyxiant. It blocks the normal transfer of oxygen to the body’s tissues and organs. You can collapse, enter a coma or die from respiratory failure from only inhaling a few breaths. It has a very characteristic smell - rotten eggs. However, at high concentrations hydrogen sulfide paralyses the sense of smell. The gas is colorless, flammable and is heavier than air. Headaches, dizziness, burning eyes or nausea can be signs you where exposed to H2S. It is easy to detect concentrations as low as 1 ppm. Exposure to concentrations above 15 ppm should not occur without appropriate breathing apparatus.

Carbon Dioxide is colorless, odorless and heavier than air. Although naturally occurring in human respiration in high concentrations it can cause asphyxiation or respiratory distress. It is of particular concern in enclosed spaces because humans cannot breathe air containing more than 10% CO2.

Ammonia is a colorless lighter than air gas with a very pungent odor. It causes asphyxiation/ respiratory distress/irritation and eye irritation. Most people can detect ammonia at levels below 5 ppm. Ammonia levels above 20 ppm are easily detectable and are a strong indicator corrective measures need to occur. Exposure to ammonia concentrations above 35ppm should not last longer than 5 minutes without breathing apparatus.