Oxygen rebreather

Oxygen rebreather is a type of breathing apparatus that absorbs the carbon dioxide of a user's exhaled breath to permit the re-breathing (recycling) of the substantially unused oxygen content of that breath. Oxygen rebreathers are used in environments where breathable oxygen is limited or absent, for purposes such as underwater diving, space exploration, and high-altitude climbing. Unlike open-circuit scuba diving systems, which expel the exhaled gas into the water, rebreathers reprocess the exhaled gas and provide it back to the user, making them more efficient and minimizing bubbles, which is particularly useful for underwater photography, wildlife observation, and military covert operations.

Design and Operation

The basic components of an oxygen rebreather include a breathing loop (mouthpiece, hoses, counterlung), a means of carbon dioxide removal, an oxygen supply, and a method for adding oxygen to the loop to replace the amount metabolized by the user. The carbon dioxide is absorbed by a chemical scrubber, usually containing soda lime, allowing the remaining oxygen to be breathed again.

Oxygen rebreathers supply a constant partial pressure of oxygen and are most commonly used at relatively shallow depths due to the risk of oxygen toxicity, which increases with pressure and hence, depth. They are simpler and lighter than other types of rebreathers, such as semi-closed or closed-circuit mixed gas rebreathers, but their use is limited by the depth and duration due to the aforementioned risk.

Applications

Oxygen rebreathers have a range of applications:

- **Military and Special Forces**: For covert operations where bubbles can reveal diver positions. - **Scientific Research**: For underwater studies where minimal environmental disturbance is required. - **Space Exploration**: In space suits for extravehicular activities, where recycling oxygen is crucial due to limited supplies. - **High-Altitude Climbing**: In closed environments or where carrying oxygen tanks is impractical.

Safety and Risks

While oxygen rebreathers are efficient and have various applications, they come with risks, primarily oxygen toxicity, which can lead to convulsions and unconsciousness underwater. Users must be trained to monitor their depth and exposure time to manage this risk. Additionally, the scrubber's efficiency in removing carbon dioxide can diminish, leading to a buildup of CO2 in the breathing loop, which can cause hypercapnia. Regular maintenance and understanding the equipment's limitations are crucial for safe operation.

Advancements

Technological advancements in oxygen rebreather design continue to improve their safety, efficiency, and usability. Innovations include better materials for CO2 scrubbers, more reliable oxygen sensors, and integrated computers to monitor and adjust the oxygen levels automatically, enhancing both safety and user experience.

See Also

• Scuba diving
• Underwater diving
• Hyperbaric medicine
• Space suit

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