Forgive this extremely naive question from a bloke who only flies as a passenger a couple of times a year but should this situation happen to me, once the mask has dropped and I have put it on and pulled the tube, just how would I know it was working properly and O2 was coming through? Would I feel a draught of cold 'air' or something? Or would there be a smell and/or taste?
I would imagine that even if it was practical to make some sort of announcement during the rapid decent a significant number of passengers would be so scared that they would not take it in. I would therefore agree with the suggestions that a rapid descent is very likely under these circumstances with no announcement at the time should be mentioned in the safety briefing.