Answer:
What can fill a room but takes up no space?
My second is performed by my first. A thief by the marks of my whole might be caught. What am I?
I am a busy worker who is a water mammal.
I have cities with no people forests with no trees and oceans with no water.
I'm tall I'm round and hollow Seems to get chewed a bit But you'll rarely see me unless the other end is lit.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?