1. Combustion- Hydrocarbons are subjected to "flame combustion or catalytic combustion" when they react and form carbon dioxide and harmless product water.
2. Absorption- By the use of liquid absorbent. The liquid absorbs the harmful gaseous pollutants present in the air.
3. Adsorption- The gaseous pollutants are adsorbed at the surface of the process solid and clean the air passes through it.