Four methods, can be used to control the air pollution, mainly of the gaseous contaminants, which are given below :-

A) Absorption in Liquid :-

• In this the effluent gases are passed through a selective liquid in wet scrubbers, packed towers.
• The toxic gases such as the sulphur dioxide, hydrogen sulphide, hydrogen chloride, ammonia etc. are controlled by this method :-

Advantages :-

• It is cheap method to control Air pollution.

• A small spaces is required for the process.

B) Adsorption on solid surface :-

• The Polluted gases are allowed to pass through absorber; which have solids of porous structures.

• In this method Activated carbon, alumina, silica gel are used as the adsorbents, to remove toxic gases.

C) Condensation to a liquid :-

• The toxic vapour is converted into liquid by condensation.

• For this the condensers are installed ahead of pollution control units.

Advantages :-

• It helps to recover valuable products from the gases.

• It helps to remove the components which may cause corrosion to other equipments.

D) Conversion to a less toxic gas of Non-Polluted gas :-

• To control the organic gas emission, the system of the combustion of combustible components into water is used.

• The equipments used for this process are flame incinerators after burners, flares etc.