For background, if you're unfamiliar, hypoxia is when you don't get enough oxygen in your system so you start shutting down. It happens in low pressure (high altitude) conditions and is associated with feelings of euphoria, drunkenness, numbness, air hunger, nausea, confusion, slow reactions, etc.
For the chamber, you're subject to 25kft pressure without your mask and given easy math/logic questions to answer. You'll hear the aircrew in the video tell the subject to gangload the regulators (switches up for max O2 output) + put his mask back on when his symptoms start getting bad.
If you're a cadet and there's an altitude chamber around that you can get to, I definitely recommend doing it because then you can hitch fam rides at local bases (esp around training bases) a lot more easily + it's just a crazy experience.