Air Quality Index, or AQI, is a nationally uniform index for reporting and forecasting daily air quality.
It is used to report the five most common ambient air pollutants that are regulated under the Clean Air Act: ground-level ozone, particle pollution (particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.
The AQI tells the public how clean or polluted the air is and how to avoid potential associated health effects.
The AQI uses a normalized scale from 0 to 500.
The higher the AQI value, the greater the level of pollution and the greater the health concern.
AQI values below 100 are generally considered to be satisfactory.
When AQI values are above 100, air quality is considered to be unhealthy, at first for members of susceptible populations, then for everyone as AQI values get higher.
The AQI is divided into six categories that correspond to different levels of health concern.
Good 0- 50: Air quality is excellent and poses little or no risk.
Moderate 951 – 100): Air quality is acceptable; however, there may be some health concern for a small number of unusually sensitive individuals.
Unhealthy for Sensitive Groups (101 – 150): When air quality is in this range, people that are included in a sensitive group, whether the sensitivity is due to medical conditions, exposure conditions, or inherent susceptibility, may experience the effects when engaged in outdoor activities.
Unhealthy (151 – 200): When air quality is in this range, any individual who is active outdoors may experience the respiratory effects.
Very Unhealthy (201 – 300): When air quality is in this range, it is expected that there will be widespread effects among the general population and more serious effects in members of sensitive groups.
Hazardous (301 – 500): If air quality gets in this range, it will trigger health warnings of emergency conditions and there will be widespread coverage in the media.