It just occurred to me.

It kind of stinks. "When astronauts return from space walks and remove their helmets, they are welcomed back with a peculiar smell. An odor that is distinct and weird: something, astronauts have described it, like "seared steak." And also: "hot metal." And also: "welding fumes." (What Space Smells Like ). "Space, three-time spacewalker Thomas Jones has put it, "carries a distinct odor of ozone, a faint acrid smell." Space, Jones elaborated, smells a little like gunpowder. It is "sulfurous."

Of course this is the smell present after astronauts have come back into the ISS since there is no air in space to smell. The smells reported are what are sensed after removing their helmets in the ISS airlock.