Pass it if you've got it

Similar to the tobacco-themed "take a break" saying, this phrase refers to an occasional interval during travel or work when anyone in the party who has previously been "holding it in" is now permitted to "let fly" as much as he/she desires, even if said eruptions are obscenely loud and/or odiferous. Further explanation unnecessary.

Hippie-bus driver: Okay, folks --- we're about to cross the Passagassawakeag bridge, so I'm lowering the windows --- feel free to pass it if you've got it!