How Does a Nuclear Submarine Make Oxygen?

Nuclear submarines can remain submerged for months because they produce their own air. Electrolysis units pass electric current through purified seawater, breaking water molecules into oxygen (piped into the ventilation system) and hydrogen (expelled overboard). Carbon dioxide is removed by chemical scrubbers using monoethanolamine or lithium hydroxide canisters. The nuclear reactor provides virtually unlimited electrical power for these systems. A crew of about 130 on a U.S. Virginia-class submarine consumes roughly 2,500 litres of oxygen per hour, all generated onboard.