Some 737 O2 discussion here on Pprune
http://www.pprune.org/tech-log/29883...le-oxygen.html
This link indicates that at least one portable bottle is pressurized to 1800psi with a flow rate variable to deliver between 7 and 70 minutes.
Are all ten or so portable bottles the same specification?
It raises the issue of hypothermia on the flight deck and instruments freezing (?) if the plan was to keep cabin depressurized beyond the endurance of the emergency O2 supplies available to cabin crew.
Or does 777 have cockpit heating that overcomes the issue, if so can it work for an hour or more?
Mickjoebill