Have you ever wondered how nuclear submarines create oxygen for their entire crew for long periods at a time?
You would probably think that in order to supply the entire crew of a nuclear submarine with sufficient oxygen you would just load op a good couple of oxygen tanks and then be on your merry way. However, tanks are incredibly heavy and they will inevitably run out as nuclear submarines are designed to stay submerged for as long as possible.
First of all, oxygen in a submarine is more valuable than gold, so every compartment is carefully monitored by a system called CAMS (Central Atmospheric Monitoring System). It detects which compartments require more or less oxygen depending on how much carbon dioxide is present. If more people occupy a compartment, more carbon dioxide is released and detected, therefore more oxygen is released into that compartment and vice versa.
Nuclear submarines also have an oxygen making solution onboard. Oxygen is made by the use of electrolysis. All you need, fundamentally, is saltwater and electricity. But, in order for the electrolysis apparatus to not produce any toxic byproduct, the system becomes a whole lot more complicated. The salt water needs to be distilled before use by means of reverse osmosis and, on top of that, a lot of electricity is needed to produce the required amount of oxygen. But, hey, these submarines have a nuclear reactor onboard, so that isn't necessarily a problem.
Take a look at the video below by YouTube channel, Smarter Every Day, on How Do Nuclear Submarines Make Oxygen?- Smarter Every Day 251