The major contributor of carbon-monoxide is
Automobiles
Air is said to be polluted when there is any change in the required amounts of any of the components of air or when foreign substances mix with air. The table given below shows air pollutants and their major source:
Air PollutantSourceCarbon monoxideAutomobilesCarbon dioxideBurning of coal and woodSuphur dioxideBurning of fossil fuels
The major contributor of carbon-monoxide is smoke from automobiles.