I found that for me smell is extremly connected to memory. I'll smell something and instantly it will bring up some distant memory. Or I'll be doing something unrelated, the thought comes to mind, and the smell reappears although the thing the first produced the scent is not present.

For example, after a day of hunting and having to gut deer, and go somewhere else having washed, smell another source of methane, and immediately I smell deer guts.

Or the fact I constantly smell what I believe to be the milking parlor of a dairy farm while working underground in the coal mine.

Weird stuff