An air quality index (AQI) is used by government agencies to communicate to the
public how .... On occasion, when the amount of air pollution is abnormally high,
the .... The CAI is on a scale from 0 to 500, which is divided into six categories. ....
over 300 represents hazardous air quality and below 50 the air quality is good.
Air Quality Index
Follow recommendations for the Hazardous category. Additional information on
reducing exposure to extremely high levels of particle pollution is available.