I looked around this morning and noticed...
When you try to walk into the entrance from the production lines you end up in the slig bunks.
When you take the southern exit from the production lines catwalk to the corridor you pass through a tiny, bizarrely coloured room en-route.
You can't go down the back stairs.
Also, I wasn't able to get into the lab or the stockyards, but this might be because you haven't done them yet.
