Air Quality Index (AQI) Basics


Air Quality Index (AQI) is way to measure Daily Air Quality . It helps us to understand  how clean or polluted our air is, and what associated health effects might be a concern for us. The AQI focuses on health effects we  may experience within a few hours or days after breathing polluted air.

How is AQI calculated ?

  1. The Sub-indices for individual pollutants at a monitoring location are calculated using its 24-hourly average concentration value (8-hourly in case of CO and O3) and health breakpoints concentration range. The worst sub-index is the AQI for that location.
  2. All the eight pollutants may not be monitored at all the locations. Overall AQI is calculated only if data are available for minimum three pollutants out of which one should necessarily be either PM2.5 or PM10. Else, data are considered insufficient for calculating AQI. Similarly, a minimum of 16 hours’ data is considered necessary for calculating sub index.
  3. The sub-indices for monitored pollutants are calculated and disseminated, even if data are inadequate for determining AQI. The Individual pollutant-wise sub-index will provide air quality status for that pollutant.
  4. The web-based system is designed to provide AQI on real time basis. It is an automated system that captures data from continuous monitoring stations without human intervention, and displays AQI based on running average values (e.g. AQI at 6am on a day will incorporate data from 6am on previous day to the current day).
  5. For manual monitoring stations, an AQI calculator is developed wherein data can be fed manually to get AQI value.

How Does the AQI Work?

Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air  quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level CPCB has set to protect public health. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.

Central Pollution Control Board, Ministry of Environment, Forest and Climate Change, Govt. of India manage a portal where we can check live AQI of different city of India. you can check using this link


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