Farts? Between this and your Pointless Barf Observations Diane, I am becoming quite disillusioned.
Anyway, the best way to handle number one, is to simply tell the passerby “Excuse yourself, please. That was foul.” Ya gotta take the initiative and blame them.
The elevator scenero happened to me at work, in the bathroom. The place was empty, except for the stench-o-rama going full tilt. I sidle in and innocently pee, and of course I’m joined by someone who must assume the stink originates with me.
I hopefully solved it by hollering, “Peee-yooooo! My, it stinks in here, doesn’t it?” Fortunately we all know one another pretty well. If they chose to believe it’s a cover-up, well, they’ve got a comeback if I ever act like my shit don’t stink.
Ummmph! I was hoping that thread was long and forgotten, UncleBeer, but nooooooooooooo, you just HAD to bring it back to life, didn’t you.
Guess I’m going to go make some. . . er . . . alterations, to that very nice e-mail I have been working on for you. Ya Butthole. 
Zette (love you too ;)), I love fart and poop jokes!!! There is nothing funnier!
Standard proceedure! Unfortunately, I was afraid they would smell the fart and get even with me while I was “down there”. One stink ass was more than I could handle at the moment.