Farts are indeed flammable and people with more matches than sense try to prove this all the time.
Many of them get their body hair singed, or worse.
One statistic indicates that close to one-quarter of the people who try this get burned.
Methane and hydrogen are both in farts and are both flammable gases.
Word has it that the results tend to be yellow or blue flames, they can’t always be easily seen.