Can Farts Be Set On Fire?

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It is possible to set farts on fire, but you probably won’t be able to create a full-size flamethrower from your backside.

I remember watching cartoons for hours as a child, and oddly enough, some of the parts I can most vividly remember are where the cartoon characters would set their farts on fire!

Now that I have the expertise to scientifically study this hilarious yet dubious phenomenon, I set out to find out if this is actually possible.

Short answer? Yes, it is. You can set your farts ablaze, but could it be enough to create a flamethrower out of your behind?

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What Are Farts And How Are They Produced?

A fart is nothing but gas produced by the gut that escapes out through the bum. There are four possible reasons for such gas buildups in our bodies.

Air

While eating or drinking, instead of air going down our windpipe, it can go down our food pipe and enter the digestive system. This air will follow the same path as the food we eat after entering our mouths and come out from our butts… as farts!

Blood

Sometimes, gases like oxygen or carbon dioxide that flow in our blood can diffuse into the intestine and gradually build up inside.

Digestive Processes

There are two possible moments where gas may be formed in our body during digestion.

First, when food is being digested by our acidic and enzyme-rich gastric juices, they break down the food to release carbon dioxide. This is because, if we eat any basic food (foods with pH higher than 7), it reacts with our stomach acids to generate carbon dioxide. After all, acids react with carbonates (common additives in bread) to produce carbon dioxide as a byproduct.

Gut Bacteria

Second, bacteria that help to digest our food release gaseous byproducts. This is the part we’re interested in: food + gut bacteria + body heat = flammable gas.

Picture a plate of carbohydrate-rich foods – broccoli, beans and cabbage. A common property of these foods is that they contain tough-to-digest carbohydrates. Our gut doesn’t have the equipment to digest certain complex carbohydrates, but our gut bacteria can.

So, undigested, the complex carbohydrates make their way into the colon, where they are snacked on by gut bacteria. The gut bacteria ferment these sugars and give out two gases in particular that answer our main question – Hydrogen and Methane.

The Different Gases In Farts

Now that we know how farts are formed, we should also know what kind of gases are in our farts. One particular study has detailed the contents of our farts.

Researchers fed participants either baked beans or a fiber-free liquid diet and then collected their farts using rubber tubes that were put inside their bums. After they collected the farts, they identified most of the different gases inside them.

The common gases were found to be nitrogen (the most abundant), carbon dioxide and hydrogen. Other gases found in smaller amounts include oxygen and methane.

FUN FACT: Hydrogen sulfide (H₂S) is the culprit for stinky farts. This sulfur-containing gas comes from the breakdown of certain proteins in the food we eat. So, if you want to avoid having stinky farts, the best thing to do would be to cut down on sulfur-rich foods like broccoli or Brussels sprouts.

They also found that people fart about a liter of gas a day!

Along with these gases are the two gases most responsible for such surprising and potentially embarrassing emissions—hydrogen and methane. Hydrogen can make up a significant portion of fart volume (up to 50% in some individuals), while methane is only produced by about one-third of the population and typically accounts for around 7% of the total gas when present.

Flammable Gases

Out of all the gases in our farts, hydrogen and methane are the flammable ones. Hydrogen sulfide, the gas responsible for the stinky smell, is also flammable, though present only in trace amounts. This means these gases can easily be set on fire.

Flammable gases mix readily with oxygen in the air outside our buttocks and can catch fire easily, even at low temperatures. In fact, one of our fart gases – hydrogen – is so flammable that it is actually used as rocket fuel! Note that while oxygen is present in small amounts in farts, it is not itself flammable – rather, it is an oxidizer that supports combustion.

It is mainly the hydrogen and methane content that makes farts so easy to set alight. When lit, farts often produce a blue flame, which is why the act is sometimes called a "blue dart" or "blue angel."

How Many Farts Does It Take To Light A Fire?

Now that you know your farts are flammable, that doesn’t mean you should try letting one rip with a flame near your backside. Trust me, you wouldn’t want to burn your bum.

Even though you produce flammable gases, it isn’t enough to create a flamethrower. Humans can fart anywhere between 25-100 ml at a time. That’s only enough to keep a flame going for a few seconds.

If farts were able to burn any longer, we’d probably be using them to make electricity!

Of course, large quantities of it could help our energy problem, if we could address the large quantity of awkwardness that would come from collecting farts on such a massive scale!

Let’s say that you wished to make a farted-powered flamethrower. The average flamethrower is attached to a 15-20 liter fuel tank. That means you’d have to fart 20 times more than you normally do just to get enough fuel to power up a flamethrower for a minute or two! It could be even less, considering that not all the gases in a fart are flammable.

A woman’s fart once caught fire in the middle of a surgery! In 2016 at Tokyo Medical University Hospital, a patient undergoing a procedure where a laser was being applied to her cervix passed gas. The intestinal gases ignited when they came into contact with the laser beam, and the fire spread to the surgical drape, causing severe burns to her waist and legs.

A Final Word

Plenty of research has focused on understanding how the number and intensity of our farts can vary depending on our diet. It’s quite possible to decrease the amount we fart by eating less gassy food, but I don’t think research has focused on trying to make farts less or more flammable.

While I don’t know if cartoons and movies depict realistic ways of lighting up farts, I can say this for sure – try not to fart too close to an open flame or fire, because YES, farts can light up. Whether or not it’s as easy as it seems in the cartoons, who can say, but I surely don’t intend to try it—and you shouldn’t either!