At the very end when they are pushing the door closed against mad Jen, there is a sign about Gangers only going past?
On the other side of the door is a different sign, didn't pay much attention, just vaguely noticed it
I'd interpret that as merely meaning it's too dangerous for humans through there, not that there are segregated areas.
yeah just seen it again and it said something about acid, no humans allowed! Cause it was too dangerous!