Chicago is located at the southwestern end of Lake Michigan. The sampling site is on top of a four-story building at the Illinois Institute of Technology (IIT), about 1.5 km west of the lake. IIT is located about 5.5 km south of downtown Chicago.

The area in the immediate vicinity of the site contains student housing, parking lots, and sidewalks. The area is commercial and residential with a major expressway (Interstate 90/94, or the Dan Ryan expressway) about 500 meters west of the site. A Chicago Transit Authority rail line is located about 800 meters from the site. There is heavy urban and industrial development in all directions from the site. The heaviest concentration of industrial sources are ten to 20 km to the southeast in Chicago and northwest Indiana.