Fewer pollutant emissions for better air quality.

Combustion engines are largely responsible for two types of emission: firstly CO₂ emissions and secondly pollutant emissions, such as nitrogen oxides and particulate matter. The increasing CO₂ in the atmosphere is blamed for global warming. A vehicle's CO₂ emissions are proportional to the quantity of fuel combusted.

In order to improve the air quality – above all in cities – ambitious emissions limit values are to be adhered to in the various stages of the Euro 6 emissions standard. The focus here is predominantly on nitrogen oxide (NO_x) and fine particles. Nitrogen oxides occur when nitrogen reacts with oxygen. Due to the many oxidation stages and nitrogen/oxygen compounds the nitrogen oxides are shortened to NO_x. When defining the limit values for particulates, fine particulate matter, which can pass the filter mechanisms in human mucous membranes unhindered, is a major factor. The other chemical compounds for which pollutant limits must be adhered to in certification of the vehicles in accordance with the various stages of the Euro 6 emissions standard include carbon monoxide (CO) and hydrocarbons (HC).