Carbon monoxide

Carbon monoxide is a product of combustion. It is also the most common cause of occupational gas poisoning leading to death. It is hard to detect because it has no colour or odour. It is especially dangerous in confined or poorly ventilated spaces. Recognizing the symptoms of carbon monoxide poisoning can prevent fatalities.

How workers are exposed

Running an internal combustion engine indoors or in confined areas will quickly fill a workplace with dangerous levels of the gas. On a worksite there are many possible sources of carbon monoxide, including:

  • Gas-powered engines
  • Fires
  • Natural gas space heaters
  • Furnaces
  • Kilns
  • Boilers

Workers indoors can also be exposed if vehicles idle next to fresh air intakes on the building.

The risks

When inhaled, carbon monoxide blocks the body's ability to absorb oxygen.

The gas is odourless and invisible. Workers may not know they are in danger until it's too late. How fast symptoms develop depends on various factors. How active workers are, how long they've been exposed, and the concentration of carbon monoxide all matter. Headache and nausea are the first symptoms. A coma and then death can follow.

How to reduce the risks

To reduce the potential for injury or disease, you need to control the risks and hazards in your workplace.

The most effective way to manage the risk of exposure to carbon monoxide is to eliminate the source of exposure. If that's not possible, there are other risk controls to use. When choosing risk controls, start by asking yourself the questions in the following steps, listed in order of effectiveness. See our resources for more information.

  1. 1

    Elimination or substitution

    This involves eliminating the hazard by substituting a safer process or material, where possible. It is the most effective control. A question to consider:

    • Can diesel or gas equipment be replaced by electric?
  2. 2

    Engineering controls

    Making physical modifications to facilities, equipment and processes can reduce exposure. Some questions to consider:

    • Can the equipment or tools be fitted with emissions control devices?
    • Can ventilation be improved?
    • Can building air vents be installed away from loading docks or parking garages?
  3. 3

    Administrative controls

    Changing work practices and work policies, awareness tools, and training can limit the risk of carbon monoxide poisoning. Some questions to consider:

    • Have you developed a written exposure control plan for carbon monoxide?
    • Can warning signs be posted in the work area?
    • Can signs explaining exposure symptoms be posted?
    • Can written safe work procedures be posted?
    • Can carbon monoxide monitors be installed?
  4. 4

    Personal protective equipment

    This is the least effective control. When used, there must always be at least one other control in place as well. Some questions to consider:

    • Do workers have the proper respirators?
    • Has personal protective equipment been tested to make sure it is working properly?