15000 feet is a feat worthy of praise just for the fact that he maintained his coherency unless of course he toted a portable oxygen bottle.
Oxygen is required at 15000’ but not at 14999’...I’ve been to 17000 w/o oxygen with 40 others in a DC3. It was a slow forming location as everyone was a little logy for the first half minute of a 90 sec freefall.