Vance the stuff Leo's smoking is a "space-cig", which I completely made up on grounds of real smoking being a stupid idea in spaceships. Think a mix between an e-cig and an inhaler. Electronic cigarettes produce water vapor mixed with nicotine and other chemicals, which still makes them a liability in a spaceship setting, so I just made up a small metal cylinder you suck on to get a hit of a similar mixture without producing vapors noxious to other people in an enclosed space.