The particles are very small pieces of matter measuring about 2.5 microns or about .0001 inches. The exhaust from burning fuels in automobiles, homes, and industries is a major source of pollution in the air. Some authorities believe that even the burning of wood and charcoal in fireplaces and barbeques can release significant quanitites of soot into the air. Another type of pollution is the release of noxious gases , such as sulfur dioxide, carbon monoxide, nitrogen oxides, and chemical vapors. These can take part in further chemical reactions once they are in the atmosphere, forming smog and acid rain .
Pollution also needs to be considered inside our homes, offices, and schools.
Some of these pollutants can be created by indoor activities such as smoking and cooking. It is therefore important to consider both indoor and outdoor air pollution.