Carbon Dioxide and the Rebreather Diver

Abstract

Humans produce carbon dioxide during the metabolism of oxygen and nutrients. Since exposure to high concentrations of this metabolic waste product can be fatal, the normal human body eliminates excess amounts of this poisonous gas through exhalation from the lungs. Survival depends upon proper carbon dioxide elimination and the avoidance of exposure to high carbon dioxide doses.

During open circuit SCUBA diving, the chance of becoming exposed to dangerous levels of carbon dioxide exists but is relatively limited for normal, healthy individuals using properly serviced, modern equipment. This is because the open circuit diver expires this waste gas into the water from the SCUBA unit.

Rebreathers, on the other hand, recirculate expired gas back to the diver for inspiration. Were it not for a carbon dioxide absorbent component of the breathing loop, the rebreather would also recirculate carbon dioxide back to the diver, allowing the accumulation of this toxic gas to dangerous levels.

While the overall design of rebreathers has improved much over the years, their ability to remove carbon dioxide from the breathing loop is not without limits nor is the equipment that performs this task infallible. The diver should consider these factors when electing to dive using a rebreather, and the diver should observe practices that limit the risk of carbon dioxide toxicity.


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