ReeceXFS

Hi. Sounds like a very strange title but it’s what it is. Was cleaning the car the other day and as I was by the fuel cap and quite load farting noise came from the car. (Mrs actually blamed me for it) Now I can only assume that was a rush of trapped air somewhere. But it done this again last night. Does the XF have some sort of ventilating valve of some sort for the fuel tank to release built up gasses? Any help or idea will be appreciated as I cannot seem to find anything online thanks Reece