Is the gas in the oxygen cylinder (the kind used for diving) pure oxygen? If not, what gas does it contain? What about the oxygen cylinders used in the hospital?

The oxygen we usually inhale in the air accounts for 2 1% of the air concentration, and everyone knows that there are other gases in the air. People living in such an environment are of course accustomed to such oxygen concentration. The oxygen in the oxygen cylinder is not completely pure oxygen, but the concentration acceptable to human beings. But only the oxygen concentration acceptable to adults. If the baby inhales too much oxygen from the oxygen bottle, oxygen poisoning will occur, and the direct result of poisoning is permanent blindness. A similar medical accident happened in China.