The Air Quality Index, or AQI, is an index for reporting daily air quality. It tells you how clean or polluted the air is in your region.

The U.S. Environmental Protection Agency (EPA) has developed the index, which is divided into 6 categories, indicating increasing levels of health concern.

Air Quality is based on 5 pollutants regulated by the Clean Air Act:

• Carbon monoxide
• Ground-level ozone
• Nitrogen dioxide
• Particulate matter
• Sulfur dioxide

Each pollutant has established standards which are evaluated to determine the daily AQI. An AQI value over 300 represents hazardous air quality, whereas if the value is below 50 the air quality is good.

Understanding AQI colors
Specific colors are assigned to each AQI category to make it easier for people to quickly determine whether air pollution is reaching unhealthy levels in their community.

Air Quality Index Colors

Health Concern Level	Numerical Value	Meaning
Good	0 - 50	Air quality is considered satisfactory, and air pollution poses little or no risk.
Moderate	51 - 100	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	101 - 150	Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Unhealthy	151 - 200	Everyone may begin to experience health effects, members of sensitive groups may experience more serious health effects.
Very Unhealthy	201 - 300	Health Alert: everyone may experience more serious health effects.
Hazardous	301 - 500	Health warnings of emergency conditions. The entire population is more likely to be affected.