page_title: Rebreather
section_title: Architecture of a rebreather
hierarchical_section_title: Rebreather / Architecture of a rebreather
caption_attribution_description: English: Two 3 litre, 232 bar, DIN cylinders inside a Ambient Pressure Diving Inspiration semi-closed circuit rebreather set.
context_page_description: A rebreather is a breathing apparatus that absorbs the carbon dioxide of a user's exhaled breath to permit the rebreathing of the substantially unused oxygen content, and unused inert content when present, of each breath. Oxygen is added to replenish the amount metabolised by the user. This differs from open-circuit breathing apparatus, where the exhaled gas is discharged directly into the environment. The purpose is to extend the breathing endurance of a limited gas supply, and, for covert military use by frogmen or observation of underwater life, eliminating the bubbles produced by an open circuit system. A rebreather is generally understood to be a portable unit carried by the user. The same technology on a vehicle or non-mobile installation is more likely to be referred to as a life-support system.
  Rebreather technology may be used where breathing gas supply is limited, such as underwater or in space, where the environment is toxic or hypoxic, as in firefighting, mine rescue and high-altitude operations, or where the breathing gas is specially enriched or contains expensive components, such as helium diluent or anaesthetic gases.
context_section_description: Although there are several design variations of diving rebreather, all types have a gas-tight loop that the diver inhales from and exhales into. The loop consists of several components sealed together. The diver breathes through a mouthpiece or a fullface mask. This is connected to one or more tubes ducting inhaled and exhaled gas between the diver and a counterlung or breathing bag. This holds gas when it is not in the diver's lungs. The loop also includes a scrubber containing carbon dioxide absorbent to remove the carbon dioxide exhaled by the diver. Attached to the loop there will be at least one valve allowing addition of gases, such as oxygen and perhaps a diluting gas, from a gas storage into the loop. There may be valves allowing venting of gas from the loop.
caption: Back view of a closed circuit rebreather, with the casing opened
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