I was an organic chemist, and as such worked I've worked in various "wet" laboratories. All of them had store rooms and cabinets with hundreds or thousands of bottles filled with horribly smelling goop. Besides the occasional terpenoid (naturally occurring things smelling like menthol, cloves or cinnamon) nearly everything there was liquid death.
These smells have everything: Harsh solvent-like stuff like strong alcohol or glue, rotten fish amines, off-sweet halocarbons, things like burnt plastics, excrement, or stuff that defies description as to their lingeringly terrible sensation of olfactory wrongness (selenium compounds).
There is actually a thing called "cadaverine", that should tell you enough.
Still, every sufficiently large storage space I rememebet had this identical, not unpleasant, thickly sweet, but not easily defined smell.
So to conclude, I think it's a brain glitch when we input everything, all the smells, at the same time.