It wasn't all that bad (in retrospect), but the years that I spent working as a stockboy at the local grocery store exposed me to some of lifes less pleasant smells. Since it was a small store, I had to help in the produce department. I will never forget the smell of rotten produce (especially potatoes) for as long as I live.
And every Wednesday night, I had to mop the floors of the entire store with hot water and ammonia. I won't forget that smell either.
So I haven't had it too bad.