The Ohio-class nuclear submarine was designed for extended strategic deterrent patrols. Each submarine is assigned two complete crews, called the Blue crew and the Gold crew, each typically serving 70-to-90-day deterrent patrols.
The only limiting factor to make patrols 90 days in length is food supplies. If food were not an issue, the submarines could stay submerged for years without surfacing. The submarines bring in seawater and distill the seawater into distilled water.
This water is used for showering, drinking and food preparation. Some portion of the water is converted into hydrogen and oxygen.
The hydrogen is expelled from the boat and the oxygen becomes part of the air to breathe onboard. The excess carbon dioxide is scrubbed from the air in the boat and expelled.
