It sounds like a weird question but if a place exists it needs a smell. Like would the crimson forest smell like maple syrup? Or does level 100 smell salty? Chose a level and tell me what you think it would smell like.
Anyway, I think Level 0 would smell like expired bread, Level 1 would smell like cigarette smoke, Level 2 would have a mild smell of shit (as in feces), Level 3 would be concrete dust, Level 4 would be air freshener, Level 5 would be old books, Levels 6-8 would be scentless, Level 9 and 11 would be variable, and Level 10 would be wheat if that has a smell.
Every Negative level can depend, but they would all have something weird.