$\endgroup$ – … The reason for this is interesting. We breathe air that is 21 percent oxygen, and we require oxygen to live. Pure oxygen is very harmful to humans at pressures higher than ground level, with the effects becoming worse the higher the pressure - ie. Astronauts on the International Space Station breathe air almost identical to the stuff we breathe on Earth. But to reduce the probability of decompression sickness extended prebreathing of pure oxygen over 3 to 4 hours is helpful. We breathe air that is 21 percent oxygen, and we require oxygen to live.

So you might think that breathing 100 percent oxygen would be good for us -- but actually it can be harmful. It's a little bit analogous to putting a burning tissue into an atmosphere of pure oxygen, I would think. Likewise, if you inhale pure oxygen at lowered pressure, … breathing 100% oxygen does not kill you. However, the space suits have a different pressure in them, so the astronaut can't have any nitorgen in his system when inside, or he will get the bends!This is why the astronaut has to breathe in pure oxygen during the hours leading up to a spacewalk. I don't know exactly what causes the toxicity, but I'd guess that it's related to that increased rate of oxidation. Source. I believe that, during Apollo 1, the astronauts were actually in spacesuits filled with low-pressure 100% oxygen, meaning there was no toxicity risk. This pre-breathing of pure oxygen eliminates the nitrogen from the astronaut's blood and tissues, thereby minimizing the risk of the bends. This is how the Apollo space program was able to give the astronauts 100% oxygen for an extended period of time. So, the short answer is, pure oxygen is generally bad, and sometimes toxic.

As a certified SCUBA diver, I learned that breathing pressurized pure oxygen leads to oxygen toxicity, which can be fatal.

If they didn't get rid of the nitrogen, the astronauts might get gas bubbles in their body when they walked in space. The International Space Station (commonly called the ISS) is a manned satellite that orbits our planet at an altitude of more than 200 miles. Breathing only oxygen gets rid of all the nitrogen in an astronaut's body. Dr Karl explains where it comes from. if not how they breathe impure oxygen?

The result is that free oxygen binds to the surface proteins of the lungs, interferes with the operation of the central nervous system and also attacks the retina.

At the low pressure the plasma in the blood will hold a lot less total molecules than you and I, but nearly all of them will be oxygen, unlike us air breathers with nearly 78% of the total dissolved molecules being nitrogen. Where does the oxygen come from in the International Space Station, and why don’t they run out of air? If you breathe air with a much higher than normal O2 concentration, the oxygen in the lungs overwhelms the blood’s ability to carry it away. So you might think that breathing 100 percent oxygen would be good for us -- but actually it can be harmful. So, the short answer is, pure oxygen is generally bad, and sometimes toxic. So you might think that breathing 100 percent oxygen would be good for us -- but actually it can be harmful. (For reference, the air we breathe has 21% oxygen) The use of 100% oxygen is indicated in many scenarios in the clinical setting. 10 hours at a partial oxygen pressure of 1 bar may cause a 2 % reduction of the vital capacity. Breathing in pure oxygen under normal pressure for a short period will not impact at all. However, the interior of the cabin was also pure oxygen at a little more than 1 atm of pressure; I quote a source that describes why a bit further down.
The astronaut breathes out carbon dioxide. Contrary to popular myth, hyperventilating air at ordinary pressures never causes oxygen toxicity (the dizziness is due to CO2 levels dropping too low), but breathing oxygen at pressures of 0.5 bar or more (roughly two and a half times normal) for more than 16 hours can lead to irreversible lung damage and, eventually, death. Carbon Dioxide. This will increase the amount of dissolved oxygen in your blood. For the Apollo astronauts the time when breathing pure oxygen at a pressure above 0.5 bar was limited to a few hours. To understand why, you need to go into some detail … See Full Answer. 2. At any given time, it hosts 5-6 astronauts performing a number of experiments, conducting studies and research, and doing a bunch of other stuff to enhance our …

Breathing pure oxygen i.e. Therefore, to go into a pure oxygen space suit, a spacewalking astronaut must "pre-breathe" pure oxygen for some period of time before suiting up. Ask for details ; Follow Report by Swapchatt 30.05.2018 Log in to add a comment What do you need to … 10 hours at a partial oxygen pressure of 1 bar may cause a 2 % reduction of the vital capacity.