Carbon Monoxide

Sources of Carbon Monoxide

Carbon monoxide (CO) is a harmful gas produced mainly by the incomplete combustion of carbon-containing fuels. Incomplete combustion happens when there is not enough oxygen for the fuel to burn fully, producing CO instead of carbon dioxide (CO₂).

• Common carbon fuels include petrol, diesel, coal, and wood.
• Vehicle exhausts are a major source of CO in urban areas, especially from petrol engines.
• Industrial processes that burn fossil fuels or carbon-based materials can also release CO.

For example, in a car engine, if the air supply is limited, petrol burns incompletely, producing carbon monoxide:

Fuel + limited oxygen → carbon monoxide + water

An example of a balanced incomplete combustion reaction is:

2C₈H₁₈ + 17O₂ → 16CO + 18H₂O

Properties of Carbon Monoxide

Carbon monoxide is a colourless and odourless gas, making it very hard to detect without special equipment. Despite being invisible and without smell, it is extremely toxic to humans and animals.

CO binds strongly with haemoglobin in red blood cells, forming carboxyhaemoglobin. This reduces the blood’s ability to carry oxygen around the body, leading to oxygen deprivation in tissues and organs.

Because of this, even small amounts of CO inhaled can cause serious health problems.

Environmental and Health Effects

Carbon monoxide contributes to air pollution, especially in cities with heavy traffic and industrial activity. It reduces overall air quality and poses serious health risks.

Health effects of CO exposure include:

• Headaches and dizziness
• Nausea and confusion
• Loss of consciousness
• Death in severe cases

CO poisoning is a medical emergency because it prevents oxygen from reaching vital organs.

Poor air quality caused by CO can also worsen respiratory conditions such as asthma.

For instance, if someone breathes air containing 0.1% CO, their haemoglobin’s oxygen-carrying capacity can drop significantly, causing symptoms like dizziness and fatigue. Typical safe exposure limits are much lower, highlighting the danger of CO even at low concentrations.

Prevention and Reduction

Reducing carbon monoxide emissions is vital for public health and the environment. Key methods include:

• Improving combustion efficiency: Ensuring fuels burn completely by providing enough oxygen reduces CO production.
• Catalytic converters: These devices fitted to vehicle exhausts convert CO into less harmful carbon dioxide by catalysing oxidation reactions. They typically use catalysts such as platinum or palladium to speed up the reaction.
• Monitoring air quality: Regular checks in urban areas help detect dangerous CO levels early, allowing action to reduce exposure.

For example, catalytic converters use a catalyst to speed up the reaction:

2CO + O₂ → 2CO₂