The products concerned were sold between 1 March 2015 and 10 January 2016.
The nature of this defect is that in situations where there is significant snow load on the window, the lock ring may detach itself during opening and consequently the window does not open. If there is no snow load or only moderate snow load, the window will open even with a defective lock ring.
The top sash of your smoke ventilation window has a data plate. To obtain information from the data plate the window should be activated via the comfort ventilation switch on the front face of main control panel. If your smoke ventilation has this defect, you will see the following information in the top left part of the data plate: