Air composition contains nitrogen, oxygen, noble gas, carbon dioxide, and other gases and impurities. When we talk about air pollution, it refers to the over existed of polluted gases and impurities. The air quality is judged based on the concentration of pollutant in the air. Man-made pollutant is the main source for pollution, including vehicles, ships, aircraft exhaust, industrial pollution, residents and heating burned, melting garbage pollution, etc.
When the pollution problems become more and more serious, AQI (air quality index), the dimensionless index for description of air quality condition quantitatively, becomes more important for our daily life. We will check the AQI every morning, when it is high and we will have to use protective mask to prevent inhaling more PM2.5 pollutant.
