Question 155, Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

A Descent Must Be Initiated To Prevent The Oxygen Masks Dropping When Zc Reaches 14000ft.
The aircraft has to climb to a higher flight level in order to reduce Zc to its initial value.
DELTA P will rise up to its maximum value, thus causing the safety relief valves to open.
The Crew Has To Intermittently Cut Off The Incoming Air Flow In Order To Maintain A Zero Zc.