When you swallow food, water, or saliva, you also swallow small amounts of air, which collects in the digestive system - you can have gases. They can also build up when you digest food. The body needs to get rid of the build-up by farting or burping. Some doctors say that it's normal to pass gas over a dozen times a day, and lack of gas may indicate less diversity in lower digestive tract bacteria. But this fanart No Farting Sign Sticker tells that it's forbidden to do it here.