We still don´t know if there was a real despresurization, or it was a mask malfunction. One of the few emergencies I had was taking off from STN on a charter airline B737-300, some years ago.

On climbing, the masks fell off, but we didn´t have to use them, and we landed normally shortly after. Crew told, no real despresurization.

I wonder if they were told, that descending quickly was part of the regular procedures.