I unwillingly ended up on their "smoking floor": the awful smell pervades the corridors and the rooms. You would expect the smell to disappear quickly by leaving the window open (I stayed there one week), but it does not: apparently, their "ventilation" does not bring any fresh air in but merely tries to equalize the stench in all the rooms. Also, when they do the room, they systematically close the window I had carefully left open.
They may be aware of the problem: they provide an "air freshener" and suggest we use it to mask the smells...