Answer:
(1) Carbon fuels like wood, coal, petroleum release unburnt carbon particles. Carbon particles of smoke or ash get suspended in the air.
(2) Burning of coal and diesel releases sulphur dioxide gas. It is an extremely suffocating gas.
(3) Combustion of most fuels releases carbon dioxide and carbon monoxide in the environment. It is very harmful and poisonous gas.
(4) An excessive amount of these particles in the air causes breathing problems. In winter, these particles produce 'smog'. It is very harmful to plants as well as animals.