The FAA has opportunities for a chamber ride to actually experience rapid
decompression, and we have to do it periodically in the Air Force while on
flying status. On of our classmates volunteered to take off his oxygen mask
at 25,000 feet. He turned green immediately and started seizing, and despite
being prepared, he was unable to gang load his oxygen regulator and put his
mask back on. I wonder how many brain cells he killed.

The rapid decompression was pretty uneventful- there was kind of a loud pop,
and a lot of fog. This is the result of condensation due to cooling of the
air from expansion, not moisture from our bodies.

If you ate a lot of Mexican food the night before the pain from the gas
expanding comes on the ascent, not on the descent. Likewise, ear blocks
(feels like sticking an ice pick in your ear from personal experience) comes
during descent only, as the increased ambient pressure pushes inward on your
ear drum.

The most valuable part of the ride was the ability to recognize symptoms of
hypoxia, like decreased color vision, etc. A

Anyone who ever flies over 10,000 feet (or less at night) should consider a
chamber ride a valuable and potentially life saving experience.