Quarantine is to protect your current snakes from anything the new snake could possibly have. You are suposoto use 2 different rooms, as it would be a lot harder for certain stuff to travel that far, and likely to die en route. As far as carrying germs on clothes or flesh, that's why you wash your hands after dealing with them, and the chances of it being airborn are likely to none.

For example mites, if you keep them in the same room, good chance they will get transferred, if you keep them in seperate rooms, that chance goes way way way down. Unless you don't wash your hands and stuff aswell as take the necessary precautions to preventing.