Definition
A small visual indicator built into a supplemental oxygen mask hose or regulator that shows green when oxygen is actually flowing to the user. It provides a positive, at-a-glance confirmation that the oxygen system is delivering gas through that line, distinguishing a working flow from a blocked, disconnected, or failed line.
Plain English
A little window on the oxygen line that turns green when oxygen is flowing. If you see green, oxygen is reaching you. If you don't, something is wrong.
Context Anchor
Seen when checking or using an aircraft oxygen system, especially before or during flight at altitudes where oxygen may be needed.
Why Pilots Care
Confirms oxygen is reaching the pilot, directly preventing hypoxia during high-altitude flight.
Intuition Check
Do not read the green indication as proof that the whole oxygen system is fully safe or that the oxygen supply is enough for the flight. It only shows that oxygen is flowing past that detector right now.
Example Sentence 1
After donning the mask, she glanced at the green flow detector to confirm oxygen was actually reaching her before climbing through 12,500 feet.
Example Sentence 2
During the en route oxygen check, the green flow detector remained visible, confirming continued delivery to both crew masks.