I had heard of these, but never saw a photo until now. I'd heard that they had some around Chicago, but no place or date on this photo. Apparently they were connected by underground piping to a big fan somewhere, which probably just discharged the smoke elsewhere. No stack scrubbers then.

http://abpr.railfan.net/abprphoto.cgi?j ... rr7479.jpg

Either that or the hostler was drunk and is filling the smokebox with water. I'm not sure how long the PRR used these things or where they piped the smoke to. Interesting arrangement.