Good (0 - 50): Air quality is satisfactory, and air pollution poses little or no risk.

Moderate (51 - 100): Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.

Unhealthy for Sensitive Groups (101 - 150): Members of sensitive groups may experience health effects. The general public is less likely to be affected.

Unhealthy (151 - 200): Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.

Very Unhealthy (201 - 300): Health alert: The risk of health effects is increased for everyone.

Hazardous (301 and higher): Health warning emergency conditions: everyone is more likely to be affected.