- Good-Air quality is considered satisfactory, and air pollution poses little or no risk.
- Moderate-Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
- Unhealthy for Sensitive Groups-Members of sensitive groups may experience health effects. The general public is not likely to be affected.
- Unhealthy-Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
- Very Unhealthy-Health alert: everyone may experience more serious health effects.
Hazardous-Health warnings of emergency conditions. The entire population is more likely to be affected.