Air pollution is the increase in the concentration of substances which become toxic and hazardous to the atmosphere. Industrial waste gases and burning of fossil fuels release ${\mathrm{N}\mathrm{O}}_2$ and ${\mathrm{S}\mathrm{O}}_2$ which gather in the atmosphere. During lightning, these gases form nitric acid and sulphuric acid and come down mixed with rain. Such rain is termed acid rain. Acid rains are known to cause harm to flora, fauna and infrastructures.