The following is reprinted from a post I made somewhere in 2002, updated for purposes of, well, updating. My best bud dug it up from his email and forwarded it to me.
OK, first, my qualifications as an expert on the subject, my Curriculum Fartae if you will. All statements verifiable:
2008: Repeated and multiple gaseous emissions (genus: lactose intolerance) that were of sufficient physical and sonic volume to cause a coworker to request that I attend a meeting by conference call. The meeting was 40 feet from my desk.
2001: Single fart (genus: beer and barbecue) cleared everyone off my deck, resulting in 20 people standing around thirty feet away as if they were watching a housefire.
1996: Single fart (genus: beer and beefy nachos) resulting in wife threatening divorce after I thought it would be funny to give her the old "Dutch oven" treatment (fart, hold her head under the bed covers).
1989: Falsely and repeatedly accused of flatulence by housemate when the culprit was, in fact, a collapsed cesspool that had filled the basement 3" deep with fecal matter.
1982: Single fart (genus: Matt's beer, Gibble's hot chips, and a large hoagie) clears a two-story house of three human occupants and German shepherd, with one occupant questioning the species of what may have used my rectum as a convenient tomb as he walked past holding his nose and scowling.
OK. Now: The sugars, carbs, and yeast in beer can result in the production of gas, manifesting itself as flatus. The more unfermented matter in the beer, the more likely it is that your farts will carry an odor. My empirical evidence, gathered mostly from having to sit inside a race car hauler with a bunch of guys drinking swill, is that adjuncts also can add to the gas production. Other edibles, such as cabbage, beans, onions, and bananas also can make your intestines gassy.
The rank odors come from the combination of this gas production and anything that you eat that your body doesn't enjoy digesting - for instance, beef and other red meats, being difficult to break down, are prime culprits. This is why your Uncle Stan's house smells like that - five or six beers, a golombki or two, and a nice link of kielbasa results in Aunt Carol spraying Renuzit around and sprinkling Uncle Stan's favorite chair with extra-strength pet deodorizer whenever he gets up to use the can, all the while hollering at him to "crack a damned window." Just pray he doesn't become lactose intolerant, or Muskegon's going to go up like a homesick angel the next time he's near a pilot light.
Speaking of which, much of the gas that is emitted is somewhat flammable. I swear that the only way we survived many long nights playing cards and backgammon and Risk in college was that a lighter was always on the table, ready to burn off the flatus in a rooster tail of flame as soon as someone bent over and hollered "Light me!" Sure, we ended up with a few singed shirts, but it was either that, or suffocate. Too bad that flatulent Dalmatian never stood still long enough. It's also why my friends' wives have a stash of candles on hand for poker night. The flames burn off some of the volatile gases. that circulate through the room after flatus is emitted.