|0 to 50
|Air quality is satisfactory, and air pollution poses little or no risk.
|51 to 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 to 150
|Members of sensitive groups may experience health effects. The general public is less likely to be affected.
|151 to 200
|Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
|201 to 300
|Health alert: The risk of health effects is increased for everyone.
|301 and higher
|Health warning of emergency conditions: everyone is more likely to be affected.