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Home > The ABC of air > Pollutants
Carbon Monoxide (CO)


An odourless, colourless, and flammable gas , carbon monoxide (CO) is formed during the incomplete combustion of organic matter (gas, coal, fuel oil, fuels, wood). The main source is vehicle traffic. High levels of CO can be encounter ed when engines idle or slow down in a confined space or in the event of traffic congestion in covered areas. With poorly f unctioning domestic heaters, high levels of CO can be found in homes.

Health effects

CO binds to blood haemoglobin replacing oxygen, leading to a lack of oxygen in the body (heart, brain ...). Early symptoms are headaches and dizziness. These symptoms worsen (nausea, vomiting ...) with increasing CO concentration and may, in the case of prolonged exposure, lead to coma and death.

Effects on the environment

CO participates in the ozone formation mechanisms. In the atmosphere, it turns into carbon dioxide (CO2) and contributes to the greenhouse effect.

The reference standards

Limit values
10 mg/m3 for the maximum daily rolling 8-hour average