Re: How do people capture breathable air and store it for submarines?

Greetings:

References:
1) Sport Diver Manual, Jeppesen - Sanderson Inc., 3rd Edition,
1981
2) Motion picture, Apollo 13.

At sea level the air that we breath is composed of 78% nitrogen
, 21% oxygen and 1% of other gasses including carbon dioxide. Human
breathing takes in oxygen from the air and exhausts carbon dioxide back
into the air. Nitrogen is normally breathed in and back out.

Depending on the amount of air required various techniques are used to store breathing gasses. The most simple technique is to compress ordinary air under high pressure into a pressure tank. This is what scuba divers use for breathing under water for one to two hours of diving time. One of the key components in a scuba system is the pressure regulator that supplies the air from the pressure tank to the diver at the same pressure as the water pressure at the depth were the diver is operating. At high pressures, caution must be taken to keep nitrogen bubbles from getting into the blood causing nitrogen narcosis ( commonly called the bends).

For extended periods of breathing, such as that used by pilots of high altitude aircraft, pure oxygen is stored in high pressure tanks. Because pure oxygen is highly flammable, great care must be taken in delivering pure oxygen to the pilots face masks. Also, breathing pure oxygen for extended periods of time causes irritation in the breathing passage ways in our bodies and can lead to oxygen poisoning.

In commercial aircraft flying above ten thousand feet, chemical oxygen generators are used to supply oxygen to passenger face masks during emergency depressurization situations. You can read about this system in the Mad Sci archives at the following location:

Re: Oxygen masks in aiplanes, what's the process/reaction?
Date: Fri Jun 11 12:45:13 1999
Posted By: Adrian Popa, Directors Office,
Hughes Research Laboratories
Area of science: Chemistry
ID: 928821616.Ch

The original Apollo lunar landing system used pure oxygen in the command module and the lunar landing module; however, after a tragic fire and loss of life during a training mission on the launch pad, the system was redesigned to have nitrogen and/or helium added to buffer the explosive effects of pure oxygen.

Both submarines and spacecraft now use breathing air that is similar to that on earth for long duration missions. Because we do not consume nitrogen in the breathing process it is only consumed and replaced when air leaks out of the submarine or spacecraft when the hatches etc. are opened. However, oxygen is consumed by human breathing which also causes the concentration of carbon dioxide to build up over periods of time. Thus, to avoid carbon dioxide poisoning, carbon dioxide scrubbers are used in submarines and spacecraft to filter and chemically remove carbon dioxide from the breathing air while oxygen is added to the breathing air as it is consumed. During the Apollo 13 mission, when there was an explosion in the service module on the way to the moon, one of the key problems that the astronauts faced was keeping the carbon dioxide scrubbers in operation in the lunar landing module until they could return safely to earth. Carbon dioxide poisoning was also a factor in several submarine accidents.

Best regards, Your Mad Scientist
Adrian Popa