CREW OXYGEN, PASSENGER OXYGEN AND PRESSURE INDICATIONS
The supplied system separates fixed crew oxygen, fixed cabin oxygen and portable equipment. Crew oxygen uses a cylinder, regulator, distribution shutoff and quick-donning masks; its quantity and regulated supply are different parts of the check. A mask test verifies the specified local equipment response, while the pressure/quantity check assesses the available supply against the applicable requirement. One does not replace the other. The visible panel and mask standard determine the actual controls used; do not transplant a button sequence from a different illustrated unit. [79, PDF pp. 2–10] [23, PDF pp. 1030–1031]
Normal dilution, oxygen concentration and emergency positive pressure are distinct functions on the reference crew mask. Positive pressure concerns the protection provided at the mask, not cabin pressurisation. The source describes specific automatic and manual behaviour at specified cabin conditions, but those figures are not offered as universal Fenix operating thresholds. A full-face crew mask and a passenger oxygen mask have different intended roles. The operating procedure must specify the selection required for smoke, fumes or loss of cabin pressure. [79, PDF pp. 3–9] [21, PDF pp. 92–93]
The reference cabin installation uses chemical generators feeding groups of masks. Container release and oxygen generation are separate events: the source describes electrical opening of the containers, then activation through the passenger’s mask-pull action. Chemical generation produces heat and has a finite operating period. It cannot be treated as an indefinitely supplied crew cylinder or turned into a generic mask-test action. Alternative installations and high-altitude modifications need their own effectivity; this description is not a claim that every physical generator or passenger action is independently simulated. [79, PDF p. 11]
On DOOR/OXY, distinguish cylinder pressure, regulated low-pressure indication and the supply state represented by the label. The source explicitly separates colour/attention thresholds from the requirement to check sufficient remaining quantity. A green figure is not a substitute for the applicable endurance/occupant/temperature requirements. During a pressure failure, pressure-controller information and oxygen indications belong to different systems even though both inform the response. Learn which quantity is being measured, where it is sensed and what continued capability it actually establishes. [79, PDF p. 10] [69, PDF pp. 21–22]