Exhaust gasIreland

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179. Exhaust gas

Exhaust gas is the mixture of gases and particles produced by an internal-combustion engine and discharged through the vehicle's exhaust system. It contains combustion products such as carbon dioxide and water vapour and can also contain pollutants including carbon monoxide, nitrogen oxides, hydrocarbons and particulate matter.

Modern vehicles use emissions-control systems such as catalytic converters and particulate filters to reduce harmful exhaust emissions. The amount and composition of exhaust gas depend on factors including the fuel, engine design, operating conditions and condition of the emissions-control system.

Exhaust gas
Exhaust-gas measurement on a vehicle.
Wikimedia.org • Santeri Viinamäki • CC BY-SA
What is contained in vehicle exhaust gas?

Exhaust gas contains products of fuel combustion and can include carbon dioxide, water vapour, carbon monoxide, nitrogen oxides, unburned hydrocarbons and particulate matter. The quantities depend on the engine, fuel and emissions-control system.

Why can exhaust gas be harmful?

Some exhaust components, including carbon monoxide, nitrogen oxides and fine particles, can harm human health or contribute to air pollution. Exhaust should therefore never be allowed to accumulate in an enclosed space.

How are harmful exhaust emissions reduced?

Vehicles can use technologies such as catalytic converters, particulate filters and electronic engine-management systems to reduce pollutants. Emission standards also limit the amount of certain pollutants that vehicles may produce.

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