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Carbon Monoxide (CO) – Gas Hazards & Workplace Safety

Gas Chemical Details

Carbon Monoxide is a colourless, odourless gas, to the human senses it is completely invisible. Carbon Monoxide is a highly toxic gas.  It is termed a toxic (blood) asphyxiant, meaning it reduces the oxygen transport properties of the blood.  Low ppm doses of Carbon Monoxide can cause headaches and dizziness, if the victim is removed to fresh air no permanent damage will result. High concentrations however, can saturate a person’s blood in a matter of minutes and quickly lead to respiratory arrest or death.

Occupational Health Exposure Standards

The current permissible exposure limit for Carbon Monoxide is a TWA of 30 ppm.  Short-term exposure limits (STEL) for Carbon Monoxide have been set by Worksafe Australia, taking into account the effect on the body of various exposure levels and times. The following table gives the appropriate excursion limits for different levels of carbon monoxide in the workplace atmosphere.

Total Exposure Time Allowable Concentration
15 minutes 200 ppm
30 minutes 100 ppm
60 minutes 60 ppm
Peak exposure limit 400 ppm

Effects on Humans of Gas Hazards

Although very high concentrations of carbon monoxide may be acutely toxic, and lead to immediate respiratory arrest or death, it is the long term physiological effects due to chronic exposure at lower levels that take the greatest toll of affected workers. This is the situation with regards to smokers, parking garage attendants, or others chronically exposed to carbon monoxide in the workplace. Exposure levels are too low to produce immediate symptoms, but small repeated doses reduce the oxygen carrying capacity of the blood over time to dangerously low levels.

Concentration of CO (ppm)  Effects
50 ppm Permissible exposure level for 8 hours
200-400 ppm Mild frontal heache and nausea in 2-3 hours
800 ppm Headache, dizziness and nausea in 45 minutes. Collapse and possible death in 2 hours
1600 ppm Headache, dizziness and nausea in 20 minutes. Collapse and possible death in 1 hour
3200 ppm Headache, dizziness and nausea in 5 minutes. Collapse and possible death in 30 minutes
6400 ppm Headache, dizziness and nausea in 1-2 minutes. Collapse and possible death in 10-15 minutes
12800 ppm Immediate effects-unconsciousness. Danger of death in 1-3 minutes

Causes or Source of the Gas Hazard

Carbon monoxide is produced as a by-product of incomplete combustion. It is associated with internal combustion engine exhaust, leaky heating systems, and many other common processes which involve combustion.

Applications and Industries Where Carbon Monoxide Occurs

Natural sources of CO such as forest fires create the largest amount of CO worldwide, but human-made sources such as internal combustion engines are a greater concern to workers. This is because they can produce localised high-hazard areas, particularly in confined spaces or areas where there is poor ventilation. Some of these spaces can include car parks, traffic tunnels, underground mines and many more.

Some other more specific examples can also include:

Indoor Pollution –  Many people suffer every year from carbon monoxide produced by non-automotive consumer products. These products include malfunctioning fuel-burning appliances such as furnaces, ranges, water heaters, and gas and kerosene room heaters; engine-powered equipment such as portable generators; fireplaces; and charcoal that is burned in homes and other enclosed areas.

Chemical Industry –  Carbon monoxide is an industrial gas that has many applications in bulk chemicals manufacturing.

Meat Colouring –  Carbon monoxide is used in modified atmosphere packaging systems mainly for fresh meat products such as beef, pork, and fish to keep them looking fresh. The carbon monoxide combines with myoglobin to form carboxymyoglobin, a bright-cherry-red pigment. Typical levels of carbon monoxide used in the facilities for this process are 0.4% to 0.5% of volume.


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