Air is a mechanical mixture of gases. It contains Nitrogen – 78.1%, Oxygen – 20.93%, Carbon dioxide – 0.03%. It also contains trace amounts of other gases, ammonia and water vapor.

1. Functions of air

1. It serves to maintain life through constant supply of oxygen.

2. It cools the body and helps to maintain body temperature.


3. Special senses like hearing and smell are transmitted through air.

2. Impurities of air

The various impurities that may be present in air are:

1. Products of respiration from men and animals.


2. Dusts, fumes, mist and vapors.

3. Harmful gases from industrial sources.

4. Pollutants from natural sources like bacteria, fungi and pollens.

3. Sources of air pollution


Industries: like chemical, oil, metallurgical and fertilizer industries.

Combustion: of coal, oil and other fuels at home and in industries.

Vehicles: like buses, trains and aircraft emit a variety of gases.

agriculture: which uses fertilizers and pesticides.


4. Effects of air pollution

1. Health: Increase in morbidity and mortality; Respiratory diseases like bronchitis and lung cancer.

2. Plants: spotting and burning of leaves and also retarded growth of plants

3. Animals: they suffer from toxicity of chemicals like fluorides.


4. Social and economic: Impairment of human, plant and animal growth; Corrosion of metals and building materials; cost of leaning and repair produced by these corrosions.

5. Prevention and control

1. Containment: It is prevention of the release of toxic substances into air by using devices like arrestor.

2. Replacement: Using energy sources like electricity instead of oil and coal.


3. Dilution: By establishing green belts of vegetation around industries.

4. Legislation: Like Smoke nuisance act against pollution.

5. International: By establishing international network of laboratories for monitoring and study of air pollution.

6. Disinfection of air

It can be done by:

1. Mechanical ventilation: It reduces contaminated air and bacterial density.

2. Ultraviolet radiation: It is useful in operation theaters and infectious disease wards.

3. Chemical mists: Triethylene glycol vapors are effective bactericides.

4. Dust control: By applying oil to the floor of hospital wards.