字幕表 動画を再生する 英語字幕をプリント You may have laughed at the idea of 'Silent But Deadly' farts. But is this faint flatulence really more potent than the boisterous wind you let loose? Are silent farts worse? It may surprise you to find out that a large portion of farts are the result of swallowed air. Whether from chewing a lot of gum, drinking pop, or simply from eating food, excess air enters your body and has to go somewhere. And while some is released through burping, the rest ends up in the digestive system and eventually comes out your other end. But when expelled, this gas is made of mostly nitrogen, hydrogen and carbon dioxide -- all of which are odourless. Which explains why some farts are obnoxiously loud, but contain little to no smell. The second half of the equation is gas from the large intestine. After travelling through 25 feet of small intestine, the indigestible portions of food make their way to the colon. Here, millions of bacteria feast on the remaining food, and ferment it. And this is where things can get...stinky! Though the bacteria do release some useful vitamins, they also produce chemicals containing sulfur, which is responsible for the smell in flatulence. Add to that a sulfur rich diet with things like eggs, meat or broccoli, and you're likely to produce some interesting odours. The longer these foods stay in the gut, the more they ferment and smell. Still, this smelly portion accounts for around only 1% of most farts. In the absence of the other odourless gases, however, these farts are concentrated with smell and generally quiet because there is less volume. Silent, but deadly! Having said that, loud gas can be just as smelly as the quiet ones, if the sulfur components are there. Simply put, your loud farts likely contain a higher proportion airborne, odourless gases, whereas the quieter flatulence tends to have a higher proportion of the smell. Got a burning question you want answered? Ask it in the comments or on Facebook and Twitter. And if you want the inside scoop on upcoming episode ideas and behind the scenes, check out our personal Instagram and twitter handles, and subscribe for more weekly science videos.