How is oxygen flow initiated on the Boeing 787 when deployed?

• A. By a person breathing into any one of the deployed masks in the group
• B. Automatically when cabin altitude changes
• C. When the flight deck intercom is pressed
• D. When the oxygen panel is opened

Answer: (A)

Oxygen flow in the Boeing 787 emergency system is demand-driven. Once masks deploy, the flow starts when the wearer begins to breathe through the mask. The mask has a valve that opens with inhalation, delivering oxygen as soon as you take a breath. This is why it’s not automatic at altitude, nor activated by pressing the intercom or opening the panel—the oxygen only flows when you inhale through the mask. This design helps conserve oxygen and provides it exactly when needed.