Burning Hydrocarbon Fuels
Most fuels contain hydrogen and/or carbon and/or sulphur. When burning fuel, sulphur dioxide can be produced if the fuel contains sulphur. You might also get nitrogen oxides from when nitrogen and oxygen in the air react at high temperatures (which are reached from burning the fuel). Sulphur dioxide and nitrogen oxide contribute to ACID RAIN.
Sometimes you aso get particulates (soot) which are fragments of carbon. When these build up in the air, they reduce the amount of light that can reach the earth - this is called GLOBAL DIMMING.
When carbon and hydrogen are combined with oxygen during combustion, they become OXIDISED, producing carbon dioxide and water vapour. Carbon dixiode contributes to global warming,
If there is not enough oxygen during combustion, or if the fuels are burned in low oxygen conditions, incomplete combustion occurs, which produces carbon monoxide, a poisonous gas.
You can remove sulphur from fuels before they are burned, e.g in power stations and cars.