Main article aside, I have to take the article to task for the section where they talk about an airplane and the oxygen masks that deploy when the aircraft depressurises and the passengers find it "hard to breathe".
Having gone through a depressurisation chamber as part of my flight training, at 35,000 feet (the normal cruising altitude for most passenger aircraft), it isn't actually hard to breathe. In fact, it feels quite normal. Your body just doesn't get enough oxygen into the bloodstream because the density of O2 in the stuff you are breathing in is so low, which causes onset of hypoxia.
The very reason why we do the sessions in the chamber - so that we can detect the symptoms of hypoxia particular to our own bodies, because there is normally no way to tell that you are no longer in an O2 rich atmosphere until you notice your fingernails turning blue and flashes of lights on your retina as well as feeling slightly tipsy (my own symptoms).
At higher altitudes (50,000 feet and up), then yes, there are issues because your diaphragm cannot create enough pressure differential against the outside air pressure to make you inhale and fill your lungs. My flight instructor was a test pilot in the 50's and 60's and he said when they were at that altitude, they were literally force fed liquid oxygen through their masks. They couldn't breathe it in, so they just had to open their mouths every few seconds and LOX would be shoved in (at freezing temperatures too, which used to dry out their nose, mouth and throats according to him).
> so that we can detect the symptoms of hypoxia particular to our own bodies
Destin of SmarterEveryDay (with astronaut Don Pettit) recorded his experience with that training, which included a demonstration of the effects of hypoxia on his decision making ability. He doesn't notice the rapidly increasing symptoms:
>> [Destin fails child's shape toy test, saying the cross was a square] "Alright you're starting to have a little shake there, you know from your lack of oxygen. You need to start thinking about getting back on oxygen now Destin."
>> "How would you correct for that? Can you correct for hypoxia for me?" [Destin just sits looking confused] "Alright sir if you don't get on oxygen, you're going to die. Go to your regulator, get all three switches on your regulator..." [Destin looking even more confused: "I don't want to die"]
>> [they get him back on O2, fixing everything in seconds]
Ah, that brings back memories. That was the exact stuff we did, except that my exercises was to count backwards from 1000 by 13's.
We were told that we could possibly make it 3 to 4 minutes at FL250 before having to go back onto oxygen. I managed to get to 5 minutes, but was was pretty much useless after the 3rd minute. I started to feel a real out of body experience, and it was like I was watching my own body do stuff but I couldn't really control it. I managed to get my own mask on and gangload the 3 switches, but I remember watching my colleagues in the chamber struggle and they had to be assisted by the RAAF team. The guys outside the chamber kept a hawk eye watch on all of us, and the guy in the chamber were quick to assist those of us who were in trouble.
What amazed me was as soon as we 'gangloaded' the switches to go back on full O2 with the masks on, recovery to full lucidity was super quick - within 1 or 2 seconds. It wasn't gradual, it was as if someone just whipped a heavy blanket off your brain!
Side story - before we went into the chamber, we had to be fitted for our helmets and masks, and I was seated in the 'fitting chair' in the crew room as 3 RAAF specialists slapped a bone dome and mask on me. Unbeknownst to them, that mask had just come back from a test facility, and thus it still had the wax seal on the end of the O2 hose to the mask.
Normally, there is no seal, so when the mask is clipped on during a test, you can still breathe normally as the valve at the open end just opens and shuts with your lung pressure. With the wax seal on it though, NO air gets through.
It was a few seconds of odd feeling when they snapped the mask on and I tried to breathe in but nothing happened. I remember feeling really freaked out at the sensation of wanting to breathe, but feeling and experiencing absolutely nothing. I started to grapple with the mask release, but they thought I was just uncomfortable with the fit and they kept slapping my hands away and adjusting the side straps.
I went into panic mode, and I am not sure what prompted me, but I started reeling in the trailing hose from my mask and lifted it up to see the seal on the end. One of the crew saw it and exclaimed before grabbing the hose and ripping the seal off. I gulped down lungfuls of air. Not the best start to my first chamber session!
I watched this a few months ago for the first time - it blew my mind. Made it completely clear why you're instructed to put your mask on first before helping others.
Having gone through a depressurisation chamber as part of my flight training, at 35,000 feet (the normal cruising altitude for most passenger aircraft), it isn't actually hard to breathe. In fact, it feels quite normal. Your body just doesn't get enough oxygen into the bloodstream because the density of O2 in the stuff you are breathing in is so low, which causes onset of hypoxia.
The very reason why we do the sessions in the chamber - so that we can detect the symptoms of hypoxia particular to our own bodies, because there is normally no way to tell that you are no longer in an O2 rich atmosphere until you notice your fingernails turning blue and flashes of lights on your retina as well as feeling slightly tipsy (my own symptoms).
At higher altitudes (50,000 feet and up), then yes, there are issues because your diaphragm cannot create enough pressure differential against the outside air pressure to make you inhale and fill your lungs. My flight instructor was a test pilot in the 50's and 60's and he said when they were at that altitude, they were literally force fed liquid oxygen through their masks. They couldn't breathe it in, so they just had to open their mouths every few seconds and LOX would be shoved in (at freezing temperatures too, which used to dry out their nose, mouth and throats according to him).