The AQI is a tool that indicates how clean - or dirty - the air is and what associated health effects might be a concern for you. The U.S. EPA calculates the AQI for five major air pollutants: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health.
An Air Quality Index of 0 - 50 is Good; 51 - 100 is Moderate; 101 - 150 is Unhealthy for Sensitive Groups (USG); 151 - 200 is Unhealthy; 201 - 300 is Very Unhealthy and 301 and above is considered Hazardous. 

AQI Resources

• Current Local Air Quality Map
• AIRNow: Current, Local and National Air Quality Information and Forecasts
• Real-Time Air Quality Data for Sites in the State of Ohio
• Nationwide Air Quality Alerts
• Air Quality Map Archives
• Subscribe to Air Quality Forecasts with EnviroFlash
• Live Weather Camera courtesy of WeatherBug and WLWT