Air quality index (AQI) Air quality index (AQI) is a simple air quality measure that runs from (best to worst quality) 0 to 500. AQI is used by government agencies to inform you about how polluted the air is. AQI can serve as general rule to how the air will effect you should you stand outside and breathe it, and can be summarized as follows (from https://aqicn.org/scale/):