Air quality indices are commonly used to indicate the level of severity of air pollution to the public. It is infeasible and perhaps impossible to formulate a universal technique for determining air quality index, one that considers all pollutants and that is appropriate for all situations. The intended use of the air quality index is to identify the vulnerable zone. There are mainly two approaches viz. single pollutant index and multi-pollutant index to determine the air quality index. Every index has its own characteristic strengths and weaknesses that affect its suitability for particular applications. An air quality index (AQI) is used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become.Public health risks increase as the AQI rises. Different countries have their own air quality indices, corresponding to different national air quality standards.