It is reassuring to know that such farts aren't really lost, just delayed. However, you should be aware that people get injured igniting flatulence. Not only can the flame back up into your colon, but your clothing or other surroundings may catch on fire. Ignition of flatulence is a hazardous practice. There have also been cases in which intestinal gases with a higher than normal oxygen content have exploded during surgery when electric cautery was used by the surgeon.
Farts tend to burn with a blue or yellow flame.
Any fart that rough I would hesitate to call a fart. Also, farts have the same temperature as the body from which they emerge, and aren't hot enough to initiate combustion. This book provides an entertaining and thought-provoking history of the fart in literature, language and society. Ben Franklin's classic Fart Proudly is still in print. Most of the photos come from old movies and political shots.