The oxygen requirements for all aircraft in BA's LH fleet are mandated by the maximum possible number of passengers. The highest BA 747 has 337 seats now but the oxygen is sufficient for well over 500 people in the event of a decompression.

The theraputic oxygen is often required for passengers in need. The CC plug the tubes in, and then call the flightdeck for us to switch it on. Before top of descent they call us again and we switch it off.