Exhaust gas does not sound and smell should be caused by improper diet, indigestion, intestinal flora disorders, constipation and other reasons, if the usual diet intake of vegetables, fruits less, eat a lot of high-protein meat or soy products, these foods in the stomach is difficult to digest, usually there is indigestion of patients due to the decline in gastric function, gastric dynamics, gastric motility is too slow to ingest food can not be effectively digested and absorbed, the food stayed in the stomach for a long time caused by delayed gastric emptying, the food stayed in the process of fermentation to produce a large amount of indole gas, which led to exhaust gas odor. Food stays in the stomach for a long time causing delayed gastric emptying, and the fermentation of food in the stomach produces a large amount of indole gas, which leads to exhaust odor. Patients with intestinal flora disorders due to the proliferation of harmful bacteria in the intestinal tract, the harmful bacteria react with the fermentation of food residues, resulting in a large amount of gas discharge, leading to particularly smelly exhaust. Patients with constipation may release sulfur-containing gases due to poor bowel movement and accumulation of feces in the intestines for a long period of time, resulting in foul-smelling exhaust.