page_title: Oxygen mask
section_title: Built-in breathing system
hierarchical_section_title: Oxygen mask / Oxygen delivery to divers / Built-in breathing system
caption_attribution_description: English: Keyport, Wash. (Feb. 8, 2007) - Navy Diver 1st class Mike Barnett and Navy Diver 1st Class Chad Christensen test built-in breathing masks inside a recompression chamber located in the dive locker at Naval Undersea Warfare Center, Keyport. The recompression chamber is used to treat diving related disorders and other medical conditions with hyperbaric oxygen therapy (HBOT). U.S. Navy photo by Mass Communication Specialist Seaman Andrew Breese (RELEASED)
context_page_description: An oxygen mask provides a method to transfer breathing oxygen gas from a storage tank to the lungs. Oxygen masks may cover only the nose and mouth or the entire face. They may be made of plastic, silicone, or rubber.
  In certain circumstances, oxygen may be delivered via a nasal cannula instead of a mask.
context_section_description: Oxygen supply to divers in decompression chambers is preferably through a built-in breathing system, which uses an oxygen mask plumbed into supply and exhaust hoses which supply oxygen from outside the chamber, and discharge the exhaled oxygen-rich gas outside the chamber, using a system equivalent to two demand valves, one upstream of the diver, to supply oxygen on demand, and the other downstream, to exhaust exhaled gas on demand, so that the oxygen partial pressure in the chamber is limited to relatively safe levels. If oxygen masks are used that discharge into the chamber, the chamber air must be replaced frequently to keep the oxygen level within safe operating limits.
caption: US Navy Divers test built-in breathing masks inside a recompression chamber
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