It depends. If I am having loose/watery BMs, I will always try to make it to the bathroom though I am sometimes unsuccessful. If my stools are firmer, I can let one squeak out and that feels nice because I don't have to interrupt whatever it was that I was doing. Sometimes I can fart while seated but I do prefer to lift, relax and allow the fart to completely exit. I greatly dislike the seated farts where the back of my buttocks are firmly pressed together and the fart must then escape forward, tickling past my woo-hoo.
Traditionally, if I am passing gas that usually means a BM is imminent. Since I became afflicted with Crohn's Disease, imminent is often changed to concurrent.
A Fart Story:
My husband and I have been married for almost 16yrs. In the first years of our marriage (and engagement) we developed a 'call sign' called: "foofy". This warning was to be used to alert the spouse that a fart was on the way and they could then decide to risk remaining in close proximity or leave. One evening in the winter, we were driving home and he dropped an SBD that STUNK. I mean, it was like a noxious green cloud hanging in the car.
I gagged and pawed for the window button, but it was so bitterly cold outside I was unable to thoroughly 'air' the car. I cried at him: "Ugh! Why did you do that with no warning, man?!" He just grinned at me and said: "Oh, foofy." Ha. Ha. Hm.
Some weeks later we were lounging in the living room and watching a movie on TV. I was seated in a corner of the couch and he was sprawled along the couch with his head pillowed on my lap. Yup. You've guessed it: I dropped a phenominal stinker of an SBD. He LEAPT upright with his face in a rictus of disgust and giving me a dirty look exclaimed: "Hey!" I grinned at him and said in a sweet/sing-song voice: "Oh, fffoooooffyyyyy."