Oxygen requirements - I don't get it!
I think I'm being stupid.
Question concerns supply requirements for supplemental oxygen for passengers in a pressurised aeroplane.
The book says:
100% of passengers: entire flight time when cabin altitude exceeds 15,000 feet but in no case less than 10 minutes.
30% of passengers: entire flight time when cabin altitude exceeds 14,000 feet but does not exceed 15,000 feet
10% of passengers: entire flight time when the cabin altitude exceeds 10,000 feet but does not exceed 14,000 feet after the first 30 minutes at this altitude.
OK so after a pressurisation failure and cabin altitude becomes 14,500 feet who decides which 30% of passengers get the oxygen and which don't?
And how does the operator know in advance how much oxygen to supply if they can't know in advance what cabin altitude the failure will cause?
I think I'm missing something very simple here