Tank-venting system
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2016 BMW 760Li, 2015 BMW 760Li, 2014 BMW 760Li, 2013 BMW 760Li, and 2012 BMW 760Li. However, it is still accessible from the selected car via links, so may be relevant.
The tank safety valve is a closed system that is bled via a carbon canister. The carbon in the canister is stored as granules. The large surface of the granules traps the fuel vapor, that occurs in the fuel tank. The carbon canister needs to be refreshed regularly in order to be able to continue to store fuel vapor. This is done by flushing it with fresh air from the intake pipe. This process is controlled by the engine control unit.