Originally Posted by Swedish Steve
This EICAS is low pressure in the flight deck, i.e. the supply valve is closed.
It is not low bottle pressure.
Originally Posted by sleeve of wizard
Swedish Steve that is not correct.
Indications
Oxygen Shutoff Valve/Indicator
The gauge on the cylinder shows cylinder pressure. A pressure transducer also measures the pressure. The information goes to the AIMS. The pressure shows on the status display. An advisory message shows if the bottle pressure goes below 500 psi.
Depends on your viewpoint. The pressure transducer shows pressure in the line between the bottle/s and the cockpit. If the bottle shutoff valve is closed, then it won't read the bottle pressure. At ground/air transition, the line bleed valve is opened and the pressure in the line is bled for 25 seconds (to atmosphere). If the bottle shutoff valves are closed, the pressure in the line will drop, triggering the EICAS message.
Seems like overkill, adding this kind of complexity and still have the crew check the supply during preflights. Then there is the possibility of valve leaks and an increase servicing (= more system disturbance, especially if there is no remote fill port)...
I'm not going to get into the fire debate... This has already been beaten to death in the hundreds of forum pages in the original and spinoff message threads relating to the MAS incident.