Carbon monoxide (CO) is produced during the combustion of fuels when there is an inadequate supply of oxygen for complete combustion.

In an ideal scenario, when a fuel burns in a sufficient amount of oxygen, the carbon and hydrogen present in the fuel fully react with the oxygen to yield carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$). This process is termed complete combustion. However, in real-world situations, conditions are often less than ideal. When the supply of oxygen is limited, incomplete combustion occurs, resulting in the production of carbon monoxide ($\text{CO}$).

Let us delve deeper into this process. Fuels such as coal, wood, gasoline, and natural gas primarily consist of carbon and hydrogen. During combustion, the carbon and hydrogen atoms in the fuel react with oxygen from the air. In complete combustion, each carbon atom in the fuel combines with two oxygen atoms to form carbon dioxide, while every two hydrogen atoms bond with one oxygen atom to produce water.

In contrast, when oxygen is scarce, not all carbon atoms can react with two oxygen atoms. Instead, some carbon atoms react with only one oxygen atom, forming carbon monoxide. This phenomenon explains why carbon monoxide is frequently generated in poorly ventilated spaces where fuels are burned, such as within a car engine or in a room with an inefficiently functioning stove or fireplace.

Carbon monoxide is particularly hazardous because it is colorless, odorless, and tasteless, making it difficult to detect. It is also toxic to both humans and animals. Upon inhalation, carbon monoxide binds with hemoglobin in the blood, obstructing its ability to transport oxygen throughout the body. This can lead to severe health issues, including death in extreme cases. Therefore, it is essential to ensure proper ventilation when burning fuels to mitigate the risk of carbon monoxide accumulation.