When coal and petroleum based fuels are burned, the products of combustion are: carbon dioxide, water, sulphur dioxide and nitrogen oxides.

If combustion takes place in an insufficient supply of air then carbon monoxide is also produced.

These products are harmful to human beings and also pollute the environment in the following ways:

1. Sulphur dioxide attacks the lungs and causes bronchitis and other diseases. It also produces acid rain.

2. Nitrogen oxides also attacks the breathing system and causes acid rain.

3. Carbon dioxide traps sun’s heat energy falling on the earth and increases the temperature which leads to global warming.

4. Carbon monoxide gas is poisonous and if it gets into our blood stream, it stops the red blood cells from carrying oxygen from lungs to the rest of the body causing suffocation and may even cause death.