The Occupational Health and Safety Guidelines for Farming Operations in Ontario were developed to highlight specific, and sometimes unique and unusual hazards on farms. They were jointly prepared by representatives of the farming community, the Farm Safety Association (now Workplace Safety and Prevention Services), the Ministry of Agriculture, Food and Rural Affairs and the Ministry of Labour.
The purpose of the guidelines is to help employers, supervisors and workers on farms recognize hazards and determine the ways they may best comply with their obligations under the Occupational Health and Safety Act (OHSA), and the relevant regulations. The guidelines provide general information to those in the workplace to help them identify specific hazards and dangerous situations. The guidelines may also provide the workplace parties with suggestions to consider in determining how to protect worker health and safety and to prevent injuries.
It is important to understand that the guidelines do not replace the laws that are in place. Employers, supervisors and workers on farms have responsibilities and rights under the Occupational Health and Safety Act and the following three regulations under the Act: Regulation for Farming Operations, O. Reg. 414/05, Critical Injury Defined, R.R.O. 1990, Reg. 834 and Occupational Health and Safety Awareness and Training, O. Reg. 297/13. The requirements in the OHSA and these three regulations must be complied with.
Employers have a legal obligation to take every precaution reasonable in the circumstances for the protection of workers; and, supervisors and workers must take appropriate steps to identify and address all workplace hazards. The guidelines are a starting point for the workplace parties to think about how to fulfill their obligations under the OHSA. Following the recommendations suggested in these guidelines does not relieve the workplace parties of their obligations to comply with the OHSA.
This is the first edition of the guidelines. They will be reviewed and updated on an ongoing basis, as needed, and expanded as new production methods and technologies emerge.
There are many examples of potentially dangerous confined spaces on a farm, including silos, grain bins, manure pits and spreaders, mixing or holding tanks, cisterns, valve pits and pump houses. Farmers and workers who enter a confined space, and those who attempt a rescue in an emergency, could quickly be overcome by a hazardous atmosphere, resulting in injury or death. For example, even a few seconds of oxygen depletion can impair brain cell function. This in turn may result in confusion and poor judgement and may compromise a worker's ability to exit the space.
This section covers the following topics:
The four main gases produced from decomposing manure are hydrogen sulfide, methane, ammonia and carbon dioxide. In high concentrations, each of these gases may pose an immediate threat to life or health of humans and livestock.
In animal housing facilities, where the manure pit is often located below the facility floor, manure gases may always be present in low concentrations. When pits are agitated for pumping, some or all of these gases are rapidly released from the manure and may reach toxic levels or displace oxygen, increasing the risk to humans and livestock.
The primary hazards of these gases are toxic or poisonous reactions in people or animals, oxygen depletion that can result in asphyxiation, and explosions that can occur when oxygen mixes with gases such as methane.
Hydrogen sulfide is considered the most dangerous of the by-products of manure decomposition. It has a distinct rotten egg smell.
At low concentrations, hydrogen sulfide irritates the eyes and respiratory tract while at moderate levels, it causes headache, nausea, and dizziness.
At high concentrations, hydrogen sulfide paralyzes the nerve cells of the nose to the point where the person can no longer smell the gas.
Hydrogen sulfide is heavier than air and will tend to settle to the lower areas of a storage facility. It can remain in high concentrations even after ventilation.
Ammonia has a distinct, sharp, penetrating odour detectable at very low concentrations. It is heavier than air and can irritate the eyes and respiratory tract at moderate concentrations. At high concentrations, it can cause ulceration of the eyes and severe irritation of the respiratory tract.
Carbon dioxide is a by-product of manure decomposition and livestock respiration. It is heavier than air and difficult to detect. It replaces oxygen in air and can act as an asphyxiate. At moderate concentrations, it causes shortness of breath and dizziness.
It is a major contributing factor to animal deaths by asphyxiation when animals are housed in buildings with faulty ventilation.
Methane is odorless and lighter than air, so it tends to accumulate at the top of covered manure pits. It is considered to be an asphyxiate at extremely high concentrations. Another key hazard associated with methane is its flammable, explosive nature. Methane is extremely difficult to detect without gas detection instruments but it should be anticipated as being present in all manure storage areas.
Silo gas is formed by the natural fermentation of chopped silage shortly after it is placed in the silo.
Though a variety of gases are released during this process, the type of silo in which the forage is stored is important in determining which gas will be predominant. For instance, in sealed silos both nitrogen dioxide and carbon dioxide are created but carbon dioxide is produced in far greater amounts. This is desirable because high carbon dioxide levels help to maintain high quality silage.
At the same time, however, this odorless and colorless gas is dangerous. This gas replaces the silo's oxygen and, in high concentrations, it gives a person little warning that he or she is about to be overcome. Because of this hazard, sealed silos are designed in such a way that entering them is unnecessary.
A variety of gases are also formed in conventional or open-top silos but nitrogen dioxide is found more abundantly. This highly toxic gas is characterized by a strong bleach-like odour and low lying yellow, red, or dark brown fumes.
Unlike carbon dioxide, nitrogen dioxide levels reach a peak about three days after harvesting and rapidly begin to decrease thereafter, particularly if the silo is ventilated. After two weeks, it is unlikely that more gas will be produced, although some hazard remains if the gas has not been able to escape the silo.
Nitrogen dioxide is harmful because it causes severe irritation to the nose and throat and may lead to inflammation of the lungs. What makes this gas especially dangerous is that low level exposure to it is accompanied by only a little immediate pain or discomfort, yet death can occur immediately.
A farmer might breathe the gas without noticing any serious ill effects and then die in his sleep hours later from fluid collecting in his lungs.
Also, many victims suffer relapses with symptoms similar to pneumonia two to six weeks after the initial exposure. For these reasons, it is extremely important for anyone who is exposed to this gas, even for a short time, to seek immediate medical attention.
Like carbon dioxide, nitrogen dioxide is heavier than air. As it is produced, it tends to settle right on top of the silage or flow down the silo chute and collect in the adjoining feed rooms or other low lying areas near the base of the silo.
Gas may even flow into the barn itself and become trapped in corners, under feed bunks, or lie low against the floor. The threat that this poses to livestock is a serious one.
For more information about the health effects of manure and silo gases, visit the Canadian Centre for Occupational Health and Safety (CCOHS) web site at www.ccohs.ca.