Just an aside - I originally thought that the circular 'table-like' structure that is beside the 'access tunnel' that Luke exits out of, was missing some of the bits on top of it later on, after Vader has 'broken off' the large piece immediately above it, to throw at Luke.
I realise now that those same pieces must have been 'ripped off' the top of it (along with other 'debris'), once the window smashed, and there was a sudden rush of 'air compression'! :)