Distillers, and in some cases oxygen generators are located. It's also where the reactor plant, electrical plant, and steam plant are controlled from - the Maneuvering Room (I'll talk about that in a bit).
Oxygen-isotope evidence from ancient zircons for liquid water at the Earth’s sur-face 4300 Myr ago. Nature 2001, 409, 178–181. [Google Scholar] [CrossRef] [PubMed] Knauth, L.P. Temperature and salinity history of the Precambrian ocean: Implications for the course of microbial evolution....
Within the confined environment in the submarine, we measured an average oxygen concentration of 20.24% (19.64 to 20.62%) and carbondioxide concentration of 0.304% (range, 0.058 to 0.647%). Gas concentrations were variable over the day but on average remained constant over the time of deployment...