I've been searching for a discussion on this for an hour or so, I'll post this info in this thread since the problem pictured is something I encountered. I had the compact air purification plant in two cities of approximately 50,000 and 30,000 in large city areas. I noticed that in my game, the plant had over-written the in-game Hydrogen Power Plant, so I decided to remove this lot from the game. I don't know if that's just because of my configuration, the N.American Deluxe game version I use, or the lot I was using to purify the air, but I decided that I'd rather have the power plant in my game instead. I deleted the files and loaded the game to bulldoze the lots in the two cities. I accomplished this with no problem and got the Hydrogen Power Plant back, but after the lots were bulldozed both cities went totally in the 'red' on the air polution scale just like the picture in the first post by the end of a two month span. I eventually just obliterated the cities and started over using the less effective air purifyer available here.
