A Brief, Respectful Guide to the Fart

A fart—known to science as flatus or flatulence — is simply intestinal gas making its exit. It may arrive quietly, with a brass-section flourish, or at precisely the wrong moment during a serious conversation. But fundamentally, it is a normal part of being a mammal with a digestive system.

Why do we fart?

There are two main sources of intestinal gas:

  • Air you swallow while eating, drinking, talking, chewing gum, smoking, or drinking fizzy drinks.
  • Gas made by gut microbes. Your large intestine is home to a huge workforce of bacteria. When they feast on carbohydrates that were not fully absorbed earlier in digestion—especially certain fibres and sugars—they produce gases as a by-product.

The body can absorb some gas, release some as a burp, and must evict the rest through the back door. This is not a personal failure, but completely normal.

What is in a fart?

Most of a fart is made from odourless gases: nitrogen, carbon dioxide, hydrogen, methane, and sometimes a little oxygen. The exact recipe varies with diet, swallowed air, and the particular microbial residents of your intestine.

This means that the vast majority of a fart is chemically rather boring. A fart is mostly air.

Hydrogen and methane can be flammable in the right mixture, which is scientifically interesting and practically an excellent reason not to conduct experiments involving candles, lighters, and your own underwear.

Why do some farts smell?

The smell is caused not by the main gases but by tiny amounts of potent chemicals—particularly sulphur-containing compounds such as hydrogen sulphide and methanethiol. These can smell like rotten eggs, cooked cabbage, or a warning from another dimension.

Foods rich in sulphur-containing proteins can make the effect stronger: eggs, meat, dairy, onions, garlic, and some cruciferous vegetables such as broccoli and Brussels sprouts. Beans get much of the blame for fart volume because their carbohydrates are enthusiastically fermented by gut bacteria, but they are not automatically the worst-smelling offenders.

Why are some farts loud and others silent?

The sound is not made by the gas itself. It is made when gas pushes past the anal opening and causes nearby tissue to vibrate—rather like a very small, highly unreliable brass instrument.

Loudness depends on pressure, speed, body position, muscle tension, and the geometry of the exit. A silent fart is not necessarily more polite.

How often is normal?

There is no universally correct fart quota. Many people pass gas several times a day, and around 8 – 14 times daily is commonly cited as ordinary. Some days are quieter; some days the gut orchestra schedules an encore.

More gas can follow a high-fibre diet, carbonated drinks, eating quickly, chewing gum (containing artificial sweeteners as a phenylalanine source), or foods that contain hard-to-digest carbohydrates — such as beans, lentils, onions, wheat, some fruits, and certain sweeteners. Lactose intolerance, constipation, irritable bowel syndrome, infections, and other digestive conditions can also increase flatulence.

https://www.nhs.uk/symptoms/flatulence

Are farts dangerous?

For almost everyone: no. Passing gas is a healthy pressure-release mechanism. Holding it in for a while is usually uncomfortable rather than dangerous, but your body is generally quite determined to settle the matter eventually.

A sudden, persistent change in bowel habits, severe abdominal pain, repeated vomiting, unintentional weight loss, blood in stool, fever, or a swollen abdomen with an inability to poo or fart deserves medical attention.

https://www.nhs.uk/symptoms/bloating

Can a fart transmit diseases?

An ordinary fart is not considered a route for passing on colds, flu, COVID, or other everyday infections. The gas itself is not a disease-delivery system.

The important exception is obvious but worth stating: if actual faecal material is present—for example during diarrhoea or poor hygiene—microbes can spread through faecal contamination. That is a hygiene issue, not a magical property of the fart. Clothing provides a very effective barrier, and washing hands properly after using the toilet remains the main event.

https://www.houstonmethodist.org/blog/articles/2020/oct/flatulence-everything-you-wanted-to-know-about-farting

Can you reduce excessive gas?

Sometimes, yes:

  • Eat a little more slowly and chew well.
  • Reduce fizzy drinks, gum, and other ways of swallowing extra air.
  • Notice patterns rather than blaming every bean indiscriminately.
  • Increase fibre gradually; a sudden leap from “occasionally sees a vegetable” to “full-time chickpea enthusiast” can be dramatic.
  • If dairy seems to be the culprit, consider discussing lactose intolerance with a doctor.
  • Do not be too quick to eliminate healthy foods permanently; the goal is a comfortable diet, not dietary exile.

In short: farts are the audible paperwork of digestion. They can be funny, embarrassing, thunderous, suspiciously warm, or catastrophically mistimed—but in the vast majority of cases, they are simply proof that your digestive system and its microbial staff are still on the job.

Do farts affect climate change?

Not in any meaningful way—at least not human farts. Although intestinal gas can contain small amounts of methane, a powerful greenhouse gas, the quantities released by people are tiny compared with emissions from fossil fuels, agriculture, wetlands, and especially ruminant livestock such as cattle and sheep.

Cows deserve their own climate chapter because their digestive systems ferment vast quantities of plant material; humans do not. Your personal contribution to global warming is overwhelmingly more likely to come from heating, transport, food production, or streaming another eight-part series than from anything emitted beneath your trousers.

So: feel free to blame your neighbour’s fart on many things. Climate collapse is not one of them.

Can you light a fart on fire?

In theory, sometimes. A fart may contain hydrogen and methane, both flammable gases. But whether it will ignite depends on the exact gas mixture, the amount of oxygen present, and several other variables that no sensible person should investigate at close range.

In practice, lighting farts is a bad idea. The possible reward is a brief, underwhelming blue or yellow flame; the possible consequences include burns, singed hair, damaged clothing, setting bedding or furniture alight, and explaining an exceptionally avoidable injury to medical staff.

Also, not all farts contain enough flammable gas to do anything at all. Many are chemically incapable of delivering the promised special effect. The safest conclusion is that your backside is not a Bunsen burner, and should not be treated as one.

Why are farts considered impolite?

Farts don't hurt anyone, while sneezing distributes your germs around you for others to breathe in. Why the first is considered impolite, while the latter causes people to say "bless you", offer you handkerchiefs, and wish you well, is one of society's great mysteries.