From the Cook County Department of Environmental Control:
Persons with heart or respiratory ailments are advised to limit activities and remain indoors.
Participants in the Partners for Clean Air Program are requested to initiate their activities. The general public can help reduce ozone levels by limiting unnecessary driving, by using public transportation, by avoiding refueling, by avoiding the use of oil base paints and solvents, the use of charcoal lighter fluid and the excessive use of home energy.
The air quality index values are forecast to be in the unhealthy for sensitive groups range for the Chicago Metropolitan Area due to Ozone.