To minimize the amount of gas astronauts release, NASA early on in space flight banned foods that were known to cause gas. According to NPR, foods like beans, cabbage, and broccoli were banned for a long time. And while some of these foods have made their way onto some astronaut menus, most are still very much limited. For astronauts heading to space these days, their list of banned foods includes (via Reader's Digest): bread (bread crumbs/small particles floating around in space are very bad), soda (space makes soda flat, which isn't palatable), salt and pepper (see bread: no crumbs or small particles in space), fresh milk (no refrigeration), pizza (dough doesn't get crispy in space) and alcohol (for obvious reasons).
But, as it turns out, the biggest threat that comes from farts in space isn't so much their flammability, but their smell — the lingering nature of the smell of farts, to be specific. On earth, there's airflow that helps dissipate a particularly nasty toot fairly quickly. In space, however, folks aren't as lucky. Living in a small, pressurized cabin doesn't provide much airflow, so smells can linger for a very long time. In an interview with Gizmodo, astronaut Mike Massimino talks about passing gas in such confined quarters: "Farts can kind of hang out. There's not as much airflow as on earth. You gotta introduce airflow to get rid of contaminants ... the nice thing to do is to go to the restroom where there's more ventilation to take the odor away."
In space, as it turns out, no one can hear you scream ... or fart — but they can definitely smell you.
