not all farts smell
fart lives matter
therapist lives matter
client lives matter
For the record, I've only farted once during a massage, but that was after the therapist's big fat Italian sausage worked me over and under. We both laughed and finished the massage. He was my regular for many years till I moved away.
Further I agree with @Bluefin growling stomachs, mine or the therapist's are annoying. So are poorly manicured hands, smelly rooms (dog, cigarette, incense etc.) and paper sheets.