Pittsburghers are all too familiar with the smell of sulfur dioxide emissions, but it's invisible. Now, residents can get a better visual of how air pollutants float across the region on a daily basis. Carnegie Mellon University’s CREATE Lab has launched PlumePGH, a new map from the makers of the lab’s popular app SmellPGH, which allows users to track the origin of pollution as well as how it correlates with reports of stinky air. The map shows the four largest emitters of SO2 and other sulfur oxides in Allegheny County: U.S. Steel's Clairton Coke Works, Irvin Works and Edgar Thomson Works, and the Cheswick Generating Station.