You call that common sense? What's the rest of the discussion been?
Should you have an explosive decompression, even with all engines (and packs) pumping out maximum air supply, you only have a very limited time of consciousness. Therefore you need to rapidly resort to emergency oxygen supplies which comes from your emergency system.....and the gauge is reading zero. Whaddya gonna do? That is what the discussion was about.
Thank you for your 'common sense' and explaining the technicalities, but you are way behind and haven't answered the question!