Well, Ady, you do make sense with how you explained that. Indeed, your parallels with coal miners does make sense to me. I think it is the fact that Luke arrives there so abruptly that has many of us confused. I do agree that not everything in the movies needs to be spelled out to the viewer, I just think that in this case, it might have helped a bit to establish where Luke was as he approached the chamber, just to help us get our bearings. I do like the idea of maybe widening the vane somewhat, just to better support the action inside.

Come to think of it, an establishing exterior shot of the vane itself, with maybe a close-up on the carbon freezing area, right at the beginning of the scene with Han at the chamber, would have have done wonders to help us understand where they are. From then on, we would have known that the entire battle between Luke and Vader takes place in the vane.