[libh8er]

Is it different if you're on the ground?

Yes. Lungs are more efficient at absorbing oxygen where the pressure is higher (eg ground). To absorb the same amount of oxygen at altiude (lower pressure) you will need to breathe oxygen rich air. It's why mountaineers carry O2.

Commercial airplanes do NOT provide air with oxygen levels higher than normal inside the cabin. Cabin pressure at cruising altitude is the equivalent of 8000 ft above sea level which is just fine if you are sitting idly.

[Bounced2X]

Yes. Lungs are more efficient at absorbing oxygen where the pressure is higher..

Thanks. Got a similar response from someone else.