Excessive swallowing of environmental air is called aerophagia, and has been shown in a few case reports to be responsible for increased flatus volume.
There are five general symptoms related to intestinal gas: pain, bloating and abdominal distension, excessive flatus volume, excessive flatus smell and gas incontinence.
The benzopyrrole volatiles indole and skatole actually have a mothball type smell, and therefore probably do not contribute greatly to the characteristic smell of flatus.
