I love when ppl use steam stacks as examples of pollution. Its literally just water vapor. Hvac alone will do this with a big enough factory.<br><br> I work in a cleanroom. in the winter it creates its own local weather, making snow because of the amount of water vapor it puts out just from the air system. Then there's water cooling and many other things that creat vapor. Talking +100 20' fans moving air through a building. It's super windy  if ur close to them. That air has to come from and go somewhere.