Where should the O2 mask be stored for emergency use?

• A. 100% Setting
• B. Diluted Setting
• C. Automatic Setting
• D. OFF Setting

Answer: (A)

The key idea is that in an emergency you want the highest reliable oxygen delivery as soon as the mask is used. The regulator that couples the mask has settings for 100% O2, diluted air, automatic regulation, or off. Storing the mask with the regulator in the 100% setting ensures immediate, full oxygen delivery when the mask is donned, which is essential to quickly counteract hypoxia at altitude. The diluted setting would provide less oxygen and isn’t appropriate for an emergency. The automatic setting depends on system sensors and could delay or vary delivery, and off stops oxygen flow altogether. So, keeping the mask ready with 100% oxygen ensures the fastest, most dependable emergency supply.