MOST farts smell unpleasant to an extent, but if yours are consistently incredibly smelly and fill a room with odour, it could be a warning sign, as it can be linked to inflammatory bowel disease or irritable bowel syndrome. Excessive smelly gas can also be due to bowel cancer – although this would also have other symptoms, including blood in your poo, a change to bowel habits, unexplained weight loss, extreme tiredness for no reason and a pain or lump in your tummy.