W140 activated carbon filter

Does anyone have experience? How do you notice that the large activated carbon filter is “congested” for ventilation? Do all the smells of the street then come inside or smell stuffy, as with “hemps in the sofa”? I have recently had such a sweet scent from the ventilation, as if it had swallowed a vanilla scent tree and did not manage to choke it out again… Thanks for hints.