What index is aqi?

Air quality index (AQI) is a dimensionless index that quantitatively describes air quality. AQI only represents the degree of pollution, not the concentration of specific pollutants. Because the concentration limits of six pollutants evaluated by AQI are different, each pollutant will be converted into air quality sub-index AQI according to different target concentration limits.

AQI*** is divided into six grades, from excellent grade I, good grade II, light pollution grade III and moderate pollution grade IV to heavy pollution grade V and heavy pollution grade VI. When the daily average concentration of PM2.5 reaches 150 μ g/m3, the AQI reaches 200; When the daily average concentration of PM2.5 reaches 250μ g/m3, the AQI reaches 300; When the daily average concentration of PM2.5 reaches 500 μ g/m3, the corresponding AQI index reaches 500.

The air quality is divided into six levels according to the size of the air quality index, which corresponds to the six categories of air quality. The greater the index, the higher the level, the more serious the pollution situation, and the greater the harm to human health.