Silent but deadly: Beware carbon monoxide poisoning hazards


Industry Manufacturing carbon monoxide CCOHS manufacturing Safety workplace

High concentrations of the gas can lead to a loss of consciousness, even death.

Exposure risk is high in steel production. PHOTO: FOTOLIA

It’s silent but deadly – a poisonous gas you can’t see, smell, taste or touch, but what carbon monoxide (CO) lacks in personality, it makes up for in potency. Carbon monoxide poisoning is responsible for hundreds of deaths and thousands of hospital visits every year in North America. The Ontario Association of Fire Chiefs reports that more than 50 people die each year from carbon monoxide poisoning in Canada, including 11 on average in Ontario.

A common and deadly hazard, carbon monoxide results from the incomplete burning of natural gas and any other material containing carbon such as gasoline, kerosene, oil, propane, coal or wood. Other sources are cigarette smoke and motor vehicle exhaust.

Internal combustion engines are the most common source of carbon monoxide in the workplace. There is also a risk of exposure in boiler rooms, warehouses, petroleum refineries, blast furnaces, steel production, pulp and paper production and welding. Emergency workers entering uncontrolled environments without wearing a carbon monoxide detector have also been subject to serious injury and even death.

When we breathe in carbon monoxide, it interferes with the ability of red blood cells to carry oxygen to the heart, brain and other vital organs. Exposure to very high concentrations can overcome a person in minutes with few or no warning signs and result in loss of consciousness or even death.


The initial symptoms of poisoning are similar to the flu (but without the fever). They include headache, tightness across the chest and shortness of breath, fatigue, dizziness, drowsiness, or nausea. As symptoms worsen the victim may experience muscle weakness, vomiting, confusion, losing consciousness and even collapse. The sense of confusion caused by this gas also interferes with the victim’s ability to realize that his/her life is in danger.

Protect your workers

Here’s what employers can do to protect workers from CO poisoning:

Install an effective ventilation system that will remove carbon monoxide from work areas.

• Maintain water heaters, space heaters and other potential carbon monoxide-producing equipment.

• Use equipment powered by electricity, batteries or compressed air.

• Use reliable personal and/or area carbon monoxide detectors set to alarm well below the exposure limit. Area alarms should give both visual and audible warnings immediately.

• Don’t allow the use of gasoline-powered engines or tools in poorly ventilated areas.

• Test air quality regularly, and prior to entry in areas where carbon monoxide may be present, including confined spaces.

• Ensure employees wear appropriate and approved respirators, such as a full-face piece, pressure-demand self-contained breathing apparatus, in areas with high carbon monoxide concentrations.

• Educate workers who may be exposed to carbon monoxide to know the sources and recognize symptoms, how to protect themselves and how to respond in case of an emergency.

Employees can help prevent poisoning by reporting any potential hazards, and looking out for ventilation problems, especially in enclosed areas where gases of burning fuels may be released. They should not use gas-powered engines in an enclosed space and emphasize they must report complaints of headache, dizziness, drowsiness or nausea.

Vigilance does not end in the workplace. Encourage workers to protect themselves at home by doing the following:

• Install carbon monoxide detectors that have both audible and visual alarms. Replace the batteries when the time on clocks is changed each spring and fall.

• Never burn anything in a stove or fireplace that isn’t vented. Don’t use an oven as a heat source.

• Do not use portable flameless chemical heaters, gas camping stoves or generators inside and never burn charcoal.

• Never run a car or truck in the garage with the door shut, or in a garage that’s attached to a house. Even idling a vehicle outdoors for a long period can expose occupants to carbon monoxide because of the potential for pulling the gas into the heating system.

For more information, visit and search carbon monoxide.

The Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton contributed this article. CCOHS provides information, training, education, management systems and solutions that support health and safety programs and the prevention of injury and illness in the workplace. Visit

This article originally appeared in the October 2018 print issue of PLANT Magazine.


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