Episode
Why Are Farts Smelly?
- Published
- Jun 13, 2026
- Duration seconds
- 244
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Summary
Here's something nobody tells you. Most of a fart has absolutely no smell. So what's actually making everyone pinch their nose? Dr Matt Agnew investigates the science of farts. How do smells actually work? What is a fart made of? And why do some foods make the whole situation so much worse? What you'll learn: Smells are tiny invisible particles floating in the air that your olfactory receptors grab and send to your brain A fart is gas made by bacteria in your intestines while they break down food Most fart gas has absolutely no smell... nitrogen, hydrogen, carbon dioxide, oxygen and even methane are all odourless The real culprit is hydrogen sulfide... just 1% of a fart but enough to clear a room Foods like beans, eggs, broccoli, brussels sprouts, garlic, onion and cheese all produce more hydrogen sulfide Most people fart between 10 and 20 times a day... farts are natural, healthy, and a sign your body is doing its job Astronauts on the International Space Station have to think carefully about farts because the gas can be trapped and even flammable Key Science Ideas: Olfactory receptors: The tiny parts inside your nose that detect smell and send signals to your brain Bacteria: Tiny living things in your intestines that help break down food... and make gas while doing it Hydrogen sulfide: The gas responsible for that rotten egg smell... and basically every bad fart ever Intestines: The long tube where food gets broken down after leaving your stomach Microbiome: The community of bacteria living inside your body doing useful work every day Fun Experiment: The Food Fart Tracker Pick two days this week. On day one eat a meal with plenty of broccoli, beans or eggs. On day two eat a meal without any of those. Pay attention to what happens a few hours after each meal. That dif…