Few people have experienced traveling into space. Even fewer have experienced the smell of space. Now this sounds strange, that a vacuum could have a smell and that a human being could live to smell that smell. It seems about as improbable as listening to sounds in space, yet space has a definite smell. Being creatures of an atmosphere, we can only smell space indirectly. Sort of like the way a pit viper smells by waving its tongue in the air and then pressing it to the roof of its mouth where sensors process the molecules that have been adsorbed onto the waggling appendage. I had the pleasure of operating the airlock for two of my crewmates while they went on several space walks. Each time, when I repressed the airlock, opened the hatch and welcomed two tired workers inside, a peculiar odor tickled my olfactory senses. At first I couldn't quite place it. It must have come from the air ducts that re-pressed the compartment. Then I noticed that this smell was on their suit, helmet, gloves, and tools. It was more pronounced on fabrics than on metal or plastic surfaces. It is hard to describe this smell; it is definitely not the olfactory equivalent to describing the palette sensations of some new food as "tastes like chicken." The best description I can come up with is metallic; a rather pleasant sweet metallic sensation. It reminded me of my college summers where I labored for many hours with an arc welding torch repairing heavy equipment for a small logging outfit. It reminded me of pleasant sweet smelling welding fumes. That is the smell of space.

From NASA
By: ISS Science Officer Don Pettit