It is a measure of how polluted the air is in a specific location at a given time. This means, that the AQI is time and location specific.
The AQI is based on measurements of various pollutants, such as :
Ground-level ozone [O3]
Particulate Matter [PM2.5] [PM10]
Carbon Monoxide [CO]
Sulphur Dioxide [SO2]
Nitrogen Dioxide [NO2]
The measurements are converted into a numerical value on a scale of 0 to 500, with higher values indicating poorer air quality.
The AQI is used by governments and organizations to communicate the health risks associated with different levels of air pollution to the general public. People can use the AQI to make informed decisions about their outdoor activities, such as whether to exercise outdoors or wear protective masks.