Again, a while since I played but I seem to remember one of the giant "air conditioning" fans was destructable. Follow your compass to see which one. I'm not too sure of that, though.
On other matters, a friend and I put together
a little guide to NecroVisioN when it was first released. There may be some things there to help, or amuse, you.
Since the game is quite old, now, we're removing the site when the current rental runs out but it's there for the moment.