Factorio Forums

I was playing a map with a max height of 320 (10 exact chunks) and found that my game was laggier than was expected. I also noticed phantom pollution squares on the top and bottom along the maps top and bottom several chunks away from my base. I was using debug info when i saw that there was a large amount of active chunks outside of the maps bounds that looked similar to a pollution cloud. Is it intended to allow pollution to spread beyond the defined edge of the map? I posted a pic on IMGUR of the active chunks.
http://imgur.com/yWqxVES
Steps to reproduce:
1. Start a map that limits width or height.
2. Make pollution. Then make more and let it spread.
3. Observe active chunks and pollution.
If needed I can provide a save but I believe this is easy to reproduce.

At least for unlimited maps i believe theres always (or at least when pollution extends your area) a ring of undiscovered but active chunks around your discovered area. I guess it's like this so that biters from these undiscovered areas also get attracted to your base