Good poop, Okie and syc I guess the pressurization profiles are close to what airlines use, i.e. 8,000 or so until "x" versus the old pressure differentials I grew up with. Have to review my Sluf manuals, but at 40K we had about 14K cockpit pressure. Our old schedule was about a 5 psi differential , so my Sluf numbers look about right. The 8K pressure is about 10 psi, and I live with that at my mountain cabin and used to go fish and hike and ski at higher alt - think 10,000 to 11,000 feet. So I guess the new folks in the b idness need more help than we had. Secondly, the oxygen concentrators like I use for COPD start to run out at 9,000 or 10,000 feet. So the OBOGS has to use bleed air, filter it, then get rid of the nitrogen and then....., or.... we could go back to the oxygen tanks most of us grew up with and all that would entail.
The local rags here in the Panhandle have several stories about the OBOGS complaints, and at one time some of the crews "went on strike", wrote letters and......
So I cannot rule out an OBOGS problem or another cockpit issue besides the oxygen system but maybe CO or other fumes. And I take it that the masks and regulators are similar to what we used in that you are not under pressure all the time and get ambient atmosphere plus oxygen until up around 25K, then get pressure.