What indicates that an oxygen mask provides proper oxygen flow?

• A. The mask changes color to green.
• B. The aircraft automatically supplies oxygen regardless of mask.
• C. There is a whispering sound when wearing.
• D. A steady oxygen flow indicator, proper mask seal, and comfortable fit with the mask delivering oxygen when worn.

Answer: (D)

Ensuring proper oxygen delivery from an oxygen mask relies on three things: a steady oxygen flow indicator showing that oxygen is actually flowing, a seal that fits well around the nose and mouth to prevent leaks, and a comfortable fit so the mask stays in place and you can breathe through it properly. When these are present, you can be confident the mask is delivering oxygen as worn. Color changes aren’t a reliable sign of flow, and the system may supply oxygen even if the mask isn’t seated correctly. A whispering sound isn’t a dependable indicator either, since it can occur for reasons that don’t guarantee proper delivery. Focusing on the steady flow indicator, a good seal, and a comfortable fit directly reflects that oxygen is reaching you through the mask.