How is aqi calculated?

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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 O
3
) and health 
breakpoint 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 PM
2.5
or PM
10
. 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.