The diesel engine has inherently low air pollution characteristics due to the nature of its combustion system. Exhaust emissions (carbon monoxide, oxides of nitrogen and particulate matter) are controlled through careful internal engine design.
A portion of the combustion chamber consists of a swirl chamber into which atomized fuel is injected under high pressure. The fuel is instantly mixed with fresh air which is swirling quickly within the chamber. This forms an air/fuel mixture yielding good fuel economy and low air pollution characteristics.