Science Buddies: "Ask an Expert"

Is pure oxygen fatal to breathe? If so, what's the science behind it? I've heard that it is, but I also know that the astronauts on Apollo 1 had a pure O2 atmosphere in their spacecraft, and were breathing pure O2 (that's why the fire spread so quickly). Why wasn't it fatal to them?

Hey,
Breating pure oxygen is bad for your body because it will make it hard for your heart to pump oxygenated blood throughout your body because your disturbing it's homeostasis. Also, when you inhale pure oxygen, your body will try and release all the carbon dioxide from your body, which is extremely dangerous. For more information go to:

http://www.sciencedaily.com/releases/20 ... 213022.htm

Apollo used pure oxygen because of the pressure in space. If you were to use "normal air" there would not be a sufficient amount of air to breathe.
For more info check out;

http://yarchive.net/space/apollo/cabin_atmosphere.html

Why did NASA keep using pure O2 in space even though they had discovered the fire hazards associated with it? Also, why doesn't pure O2 cause brain damage to the astronauts? Do they still use pure O2 on the shuttle?

Hi!
Great question! As the previous expert mentioned, pure oxygen is extremely useful in space missions, and sometimes it is important to weigh the benefits and the consequences. Pure oxygen was used in the case of the Apollo I because the alternative of using mixed gases did not allow for a breathable atmosphere. In addition, the fire safety checks assumed that there would be no flammable hazards that could pose any threat to the astronauts. Typically, the inhalation of pure oxygen can be harmful but only temporarily because it speeds up heart rate and other functions. In the context of space missions, however, it is more a matter of pure oxygen vs. no oxygen due to the pressure that is exerted once the mission enters space. Hope this helps!

Hi there,

I like the way you are thinking critically and questioning things! As indicated in your other responses, the effects of breathing pure oxygen have a lot to do with pressure. Breathing pure oxygen under high pressures (for example, while diving in the ocean) can have fatal consequences. I'm not sure how legitimate this source is, but here is a website that helps explain that: http://www.deep-six.com/page79.htm

In space, the air pressure is exceedingly low, even in the pressurized cabin of a spacecraft. That is why breathing pure oxygen in space is not fatal - the partial pressures actually experienced by the lungs are not that different from what they are on Earth at atmospheric pressure. (Atmospheric pressure at sea level is 1atm, or 760mmHg. At that pressure, the partial pressure of oxygen in the lungs is usually about 100mmHg.)

Hope that helps!

Heather