Emissions, also known as exhaust emissions, are the chemical byproducts of power generation by an engine which emerge from the exhaust system.

Though public policy tends to concentrate almost entirely on CO2 emissions, petrol and diesel fuelled internal combustion engines produce many different exhaust emissions. The main ones are:

  • Carbon dioxide (CO2)
  • Carbon monoxide (CO)
  • Oxides of nitrogen (NOx)
  • Sulphur dioxide (SO2)
  • Unburnt hydrocarbons (HC)
  • Ozone (O3)
  • Carbon particulates