Abstract
The flue gases from the combustion of fuels are considered as the main source of air pollution. Incomplete combustion yields dangerous air pollutants. In automobiles, combustion of large amounts of fuel takes place everyday usually in an incomplete conditions. Since electron emission is sensitive to the presence of carbon and oxygen, thermionic emission from platinum can be used to monitor the combustion status. A report on automobile air pollution is given and the different sensors used to monitor combustion completeness are discussed. The suggested thermionic emission sensor is then presented as a tool to detect the unburned hydrocarbons and to indicate the deviation from the optimum air-fuel ratio to achieve complete combustion.