The air quality index breaks down as follows:
- Green: value of -50 indicating Good air quality and air pollution poses little to no risk
- Yellow: value of 51 to 100 indicating Moderate air quality which is considered acceptable, but may pose a risk to some people, particularly those sensitive to air pollution
- Orange: value of 101 to 150, indicating Unhealthy for Sensitive Groups air quality, in which those in sensitive groups are likely to be affected but the general public is less so
- Red: value of 151 to 200 indicating Unhealthy air quality, in which some members of the general public could experience health effects and members of sensitive groups may experience more serious health effects
- Purple: value of 201 to 300 indicating Very Unhealthy air quality, in which the risk of health effects is increased for everyone and a health alert is issued
- Maroon: value of 301 and higher in which the everyone is more likely to affected by air quality and is considered a health warning of emergency conditions
You can also track the air quality in your zip code at the EPA's AirNow website.
Track the Chicago area's air quality below.