The purpose of the Air Quality Index or AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories. Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are provided in the chart below. EPA has assigned a specific color to each AQI category to make it easier for people to understand quickly whether air pollution is reaching unhealthy levels in their communities. For example, the color orange means that conditions are “unhealthy for sensitive groups,” while red means that conditions may be “unhealthy for everyone,” and so on.

 

Colors	Air Quality Index (AQI) Values	Levels of Health Concern	Meaning
...as symbolized by this color:	when the AQI is in this range:	...air quality conditions are:	the health implications are:
Green	0 to 50	Good	Air quality is considered satisfactory, and air pollution poses little or no risk.
Yellow	51 to 100	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.
Orange	101 to 150	Unhealthy for Sensitive Groups	Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Red	151 to 200	Unhealthy	Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Purple	201 to 300	Very Unhealthy	Health alert: everyone may experience more serious health effects.
Maroon	301 to 500	Hazardous	Health warnings of emergency conditions. The entire population is more likely to be affected.