With the recent nonattainment designation for fine particles in five central Indiana counties, Knozone Action Days will now be declared year-round when the potential exists for ground-level ozone and/or fine particles to exceed the federal standards. In some cases, Knozone Action Days may be anticipated, even though air quality levels do not exceed the federal standard because Knozone Action Days are determined using weather forecasts and predictions.

To better communicate with the general public, the U.S. EPA's Air Quality Index is now being used to convey the message that the region's air quality may become the unhealthy for sensitive groups, or the color orange, on a Knozone Action Day. On these days, businesses and individuals alike are asked to make voluntary changes to their behavior that will help improve air quality.

Knozone Action Days are usually declared by 2 p.m. the day prior to the Knozone Action Day. Knozone Action Days that fall on weekends or the following Monday are declared on Friday, if necessary. For holidays, Knozone Action Days are called the day immediately proceeding the holiday. Even when government offices are closed, staff closely monitors pollution levels and notifies the media of Knozone Action Days.

Between 10 to 15 Knozone Action Days are called in a typical summer for ground-level ozone. As a general rule, if the ozone concentration exceeds 85 parts per billion (ppb), Central Indiana has exceeded the federal air quality standard.

The city of Indianapolis began calling Knozone Action Days for fine particle levels in the fall of 2005. Data for the number of days declared will be available next year. As a general rule, if the daily fine particle concentration exceeds 65 micrograms per cubic meter, central Indiana has exceeded the federal air quality standard.