To make it easier for the public to quickly understand the air quality in their communities, EPA has assigned a specific color to each AQI category. You will see these colors when the AQI is reported in a color format in color-print newspapers, on television broadcasts, or on your State or local air pollution agency's web site.

This color scheme can help you quickly determine whether air pollutants are reaching unhealthy levels in your area. For example, the color orange means that conditions are unhealthy for sensitive groups, the color red means that conditions are "unhealthy" for everyone, and so on.

Though the AQI scale extends to 500, levels above 300 rarely occur in the United States. This website and most other references to the AQI do not list health effects and cautionary statements for levels above 300. If ozone levels above 300 should ever occur, everyone should avoid physical exertion outdoors.