Confined Space on Farm

Confined space is defined in section 264(b) of the Saskatchewan Occupational Health and Safety Regulations as: a place that has a restricted means of access or egress and poor natural ventilation and includes an open or enclosed tank vat, sewer, pipe, duct, flue, reactor, chamber and borehole.

There are many confined spaces* on a farm. Underground manure pits or tanks, open manure pits, silos, septic tanks and wells are examples. Access to confined spaces is usually restricted. Often, there is only one way in and one way out, through a small opening. Natural ventilation is usually poor.

When there is little natural ventilation, dangerous gases collect.

Dangerous Gases

The air we normally breathe consists of approximately 21 % oxygen and 79% nitrogen. In a confined space, the percentages can change quickly. The air can become deadly. Beware of manure gases and silo gas.

Manure Gases

A liquid manure holding system can contain many gases. These gases are formed as the manure rots. The gases are trapped in small bubbles and are released when the manure is agitated or pumped.

Hydrogen Sulphide (H₂S)

H₂S is often called manure gas. It is by far the deadliest of the manure pit gases. It is a clear, colourless gas. You can sometimes smell its "rotten egg odour". But, NEVER rely on the odour or lack of odour to warn you. In high concentrations of H₂S, the olfactory nerves in your nose are temporarily paralysed and you are unable to smell the rotten egg odour.

Breathing low amounts of H₂S can result in nausea, coughing, headache, dizziness and eye irritation. When people or livestock breathe high amounts of H₂S (greater than 1000 parts per million), breathing stops at once. H₂S affects the central nervous system causing paralysis of the diaphragm (which controls breathing). Once breathing stops, death will occur in minutes unless rescue is prompt. Start artificial respiration immediately.

H₂S gas is heavier than air. It tends to "pool" near the ground. Animals lying in pens are at risk to this low-lying gas. If you enter a building where there are many dead mice, cats or livestock immediately suspect H₂S gas poisoning and leave.

Carbon Dioxide (CO₂)

C0₂ is a gas that is produced by all living things, including manure bacteria. In manure pits, the C0₂ produced by the bacteria may displace the oxygen. C0₂ is also heavier than air. It is usually found at the surface of the manure.

Ammonia (NH₃)

NH₃ is colourless and lighter than air. It is easy to detect because of its sharp odour. High amounts (greater than 150 parts per million) of NH₃ can cause harsh coughing, severe irritation of the throat, eyes, and lungs. If the amounts are high enough, suffocation may result.

Methane (CH₄)

Methane is colourless, lighter than air and odourless. It is extremely flammable and explodes easily. A spark or lighted match dropped into a manure tank or pit can have deadly results. Methane is more likely to be found during warm weather (greater than 35C). It can also displace oxygen and cause suffocation.

Manure Pit and Tank Accident Prevention

Always have a helper and a mechanical lift device available when mixing or pumping manure. Tie a lifeline to anyone going into the pit or tank. Make sure he/she is wearing a self-contained breathing apparatus. A particle respirator is not acceptable.

• Force air into the pit.
• If the pit is located under a building, evacuate all the people and livestock, if possible, while the work is going on.
• If a worker feels faint or dizzy, get him/her to fresh air immediately. Be prepared to administer artificial respiration.
• Never allow the pit to become too full. Leave room for gas to collect.
• Mix below the surface of the liquid manure. This decreases the amount of gas released.

Silo Gas

To be efficient, a silo needs to be as airtight as possible. Because of the limited supply of oxygen, a silo is considered to be a confined space.

Nitrogen Dioxide (NO₂)

N0₂ is commonly called silo gas. It is DEADLY. This gas is produced during the first three weeks of the ensiling process. It appears as a yellowish-brown haze and has a bleach-like odour. But, often NO ODOUR is present. N0₂ is heavier than air. It can sometimes be seen around cracks and openings such as the feed room doors on the silo. N0₂ may also give the silage an unusual bright yellow or orange colour.

N0₂ can kill in seconds. When N0₂ enters the lungs it combines with moisture and turns into nitric acid. Nitric acid destroys the blood vessels in the lungs and causes massive internal bleeding. Death follows quickly.

Accident Prevention in Silos

Never enter a silo during filling. Adjust the distributor to spread silage properly.

• If you must enter a silo during the danger period (first three weeks), wear a self-contained breathing apparatus and a life line. Always use the buddy system. Have a helper. Be sure that your helper has the proper mechanical devices to lift you out. It is not often that one person can pull another out of a silo without the aid of a mechanical lift.
• Maintain maximum airflow when entering a silo. Always leave the blower running and open all air vents.
• Keep children, visitors and pets away from the silo during the danger period.
• If someone is found collapsed in a silo, immediately start the forage blower and ventilate the silo. This helps both the victim and the rescuer.

*Note: Multiple deaths have occurred when co-workers have attempted to rescue their friends from wells, manure pits and silos. Without the proper equipment, co-workers are also at risk of being overcome.

Resources

The Saskatchewan Farm Safety Program provides information on farm hazard identification, accident and injury prevention, and farm fatality statistics. Audio-visual materials are available free of charge on a loan basis. Video catalogues are available upon request.

For more information contact:

Occupational Health and Safety
1870 Albert Street
Regina, SK
S4P 3V7
Phone: 1-800-567-7233 toll free
Fax:306-787-2208