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Quality Contributions to the Main Motte
Contributions for the week of January 1, 2024
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While not relevant to the death penalty conversation, adding to felis-parenthesis's hypoxia stuff, I'll add first-hand experience. Part 91 regs require supplemental oxygen if you're spending more than 30 minutes at 12.5k feet above sea level, for the crew for any amount of time over 14k feet above sea level, and for all aboard for any time over 15k feet above sea level. These are not the only conditions where judgement and ability will be impaired.
(For pressurized aircraft operating under any FAA class, above 25k feet, you need both the aircraft's supplemental oxygen, and then the pilot flying additionally has to have oxygen on-hand and easily accessed, as well as alarms, because fulminant hypoxia can knock you out in seconds. Above 41k feet they have to be wearing that supplemental oxygen constantly. But you don't see that in commercial aviation unless people goofed up bad.)
10k feet above sea level is easily achieved on many non-turbocharged piston aircraft, and most people can breathe fine in most weather conditions up there. But altitude is not the only thing that impacts pressure. General aviation pilots mostly think about density altitude for takeoff and climb engine performance, as hot tarmac at high surface levels can significantly impact your max takeoff weight and climb rate. But it also changes the amount of oxygen available in every breath of air. Similarly, some levels of shorter-term anemia (and age) make people much more sensitive to density altitude changes, and some people just don't compensate as well (probably mostly genetics? Women tend to be worse-hit on average, but the worst-hit I've seen are male and don't seem to automatically breath deeper as their pulse-ox falls) .
This wouldn't be too bad if you noticed it. But low blood oxygen, especially subtle hypoxia, doesn't feel like you're drowning, or suffocating, or even like being drunk; the warning signs to look out for are difficulty with night vision and memory problems. Felis links to a video of a guy with slowed reaction times and a derpy look and some memory loss at 20k+ MSL with 60% pulse-ox (and I've seen people pass out in those conditions!), but I've seen people lose awareness at 80% pulse-ox, and their fellow pilots not noticing for ten-plus minutes -- at best, their copilots just nodded off, but more often subtle hypoxia goes from fixation on an already-completed task to simply the lights being on, but no one's home. Sometimes they'll realize that they've lost time, but it's sometimes just a headache when they get back to normal oxygen levels.
Most videos will emphasis 18k+ feet, where the impact is more immediate and more obvious to observers, because this range tends to also impact self-assessment and judgement, and because those accidents tend to involve bigger aircraft with more catastrophic impacts, while subtle hypoxia at lower altitudes is extremely hard to diagnose even among recovered or surviving pilots. But even with strict (though not always followed) rules on supplemental oxygen and common dire warnings, there are a lot of close calls and a number of likely hypoxic events at lower altitudes.
Apropos of nothing, but this is similar to what carbon monoxide poisoning survivors report. Most American smoke detectors do not also detect carbon monoxide; if yours do not, or if you're unsure, you can get reputable ones for ~30 USD/per.
If we're on the topic of carbon monoxide detectors, note that the alarms will trigger when you have deadly levels, but they generally won't go off for slow leaks. I had a coworker whose family was getting headaches, waking up tired, everyone just generally feeling cruddy. Many tests and doctors later, no answers, but doctor #3 mentioned carbon monoxide and my coworker went out to buy one with a readout. It was a carbon monoxide leak, at some fraction of the level that the alarms would go off for. He got his furnace fixed and the headaches went away.
That was enough to convince me to add one of the plug-in CO detectors with a display to my house. CO generally spreads evenly through the air, so don't worry about placing it floor level or bed height or whatever. I found a plug that we never used but was in eyeshot occasionally, and there it has sat for many years.
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