The Department of Environmental Control operates an air-monitoring network for particulate matters (less than 2.5 micrometer in diameter), sulfur dioxide, nitrous oxides, ozone, metals, and toxic air pollutants. This network includes 8 continuous sites, 8 non-continuous sites and 1 special project air toxic monitoring site. These sites are located throughout Cook County, including in the City of Chicago.
Continuous site data is pulled every hour and stored at the Department’s computer in Maywood. Daily average readings can be accessed by the public through the Air Quality Index (AQI).