The oxygen concentration was still cranked up to a hundred per cent, which, over time, can damage the lungs.

NEWYORKER: Big Med

To get around the problem, a small number of plants have evolved a way to enrich the carbon-dioxide concentration around the rubisco enzyme, and to suppress the oxygen concentration.

WSJ: Harrison H. Schmitt and William Happer: In Defense of Carbon Dioxide

Although jets are pressurized so that the cabin environment resembles an altitude of around 8, 000 feet, some people report that flying (possibly from the changes in pressure and resulting decrease in oxygen concentration) causes symptoms such as headache, fatigue and nausea.

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