From Popular Mechanics:
In 2008, Pearce was in talks with NASA to recreate the smell of space in an effort to train astronauts on the scents they might encounter in orbit.
In a video for Wired, retired astronaut Chris Hadfield confirmed that space does in deed smell like gunpowder and burnt steak."To me, it's sort of like brimstone—as if a witch has just been there," he said of the space station's airlock. He suspects that the vacuum of space may be sucking trace chemicals out of the metal walls of the spacecraft.
"Maybe it's not even coming from space, maybe it's just coming from space's effect on our ship," he said.