1. a) Any yellow alert level is equaled or exceeded at any monitoring station; and
2. b) An air pollution advisory has been in effect for 4 hours in the area for which the yellow alert is to be declared; and
3. c) Atmospheric conditions, or expected contaminant emissions, are such that concentrations can reasonably be expected to remain at or above the yellow alert level for 12 or more hours; or
4. d) For ozone, atmospheric conditions, or expected contaminant emissions, are such that concentrations can reasonably be expected to reoccur at a yellow alert level on the following calendar day.

The Director or his/her designated representative shall declare a yellow alert whenever:

(Source: Amended at 16 Ill. Reg. 8191, effective May 15, 1992)