Why can farts be set alight?

You know you've always wondered why farting on a lighter causes a brief burst of flame. Believe it or not, there is rarely any methane in farts, and so methane is not what’s burning when farts are ignited. Find out what does, and why some farts ignite and others don’t.


It’s a commonly-held belief that farts contain methane, which is why they smell and they can ignite. And this would be true, if people were cows. Actually, the gut bacteria of humans generally don’t produce methane. There are certain kinds, which live in a certain percentage of the population, that do produce methane, but it’s far from in the majority of farts.

What actually makes it through your body will depend on many things, including what you put in. Eggs, cauliflower, and meats are often more sulfur-rich and so add a little hydrogen sulfide to the final, ah, product. As for the rest, the largest component is often nitrogen, which is already a good portion of the atmosphere, and so doesn’t ignite all that readily.

What will? Mostly it’s the hydrogen in the hydrogen sulfide that’s released. Occasionally, if the person does have the lucky gut that produces methane, it will burn along with the hydrogen. In order to get the most flammable fart, people will generally eat sulfur-rich foods. It’s not a good idea to hold them in and store them up, as to those who have tested the technique a held-in fart is less likely to catch fire.

Oh, but don’t go for the matches just yet. About a quarter of the fart igniters get burned in the process. There is no way to stress how little anyone likes to get burned in that area. Worse, the ignition of the released fart can ignite gasses higher up the intestinal tract, and sometimes, high in the intestinal tract, there will be swallowed oxygen. Oxygen is swallowed daily, but generally doesn’t make it out of the body because it is so readily absorbed into cells.

Oxygen is also likely to ignite explosively if heated, and this has happened during surgical procedures carried out in the intestinal area – though there is no record of it happening when someone tried to ignite their farts. Still, it’s a bad idea to take even the most remote chance on an internal Hindenburg. Just let this knowledge seep into your mind, and keep your downstairs area well clear of it.

Via Fart Sounds




I have to wonder, when did the first homo sapiens try to light a fart on fire? Was it before the rise of hunter-gatherer societies? Did a crude ancestor try it with a pre-lit branch that had been struck by lightning before humans had mastered fire? So many fart-lighting questions!