Rebreathers

Rebreathers were the first scuba units ever used. They optimise the use of breathing gas by removing waste and recycling gas. This gives significant advantages over conventional open circit scuba that simply exhausts gas which contains alot of unused oxygen. The deeper the dive the high the ambient pressure and therefore mass of gas inhaled. Our body only requires the same fixed mass or amount of oxygen to metabolize at any depth, so rebreathers optimize the use of breathing gas by recycling. Put simply dive time is independent of actual depth. Also as there is either no or little exhaust “bubbles” both marine life is not scared off as there is little evidence of divers in the water. Rebreathers are also obviously useful for covert military operations, deep wreck discovery and underwater photography.

Operation

The waste breathing has Carbon Dioxide scrubbed away using a sodalime absorbant. Then the used oxygen (and diluent) needs replenished either manually or automatically. Levels of carbon dioxide and oxygen/helium partial pressures also has to be monitored and controlled either manually or automatically. This is all on top of all your normally diving skills, so a significant extra diver task loading creates higher risk of dive accidents.

Types

Recent technological advances has led to fully automated rebreathers purely for recreationial use called Type R as they mitigate many of these additional risks whilst using rebreathers. The manual operation of Type T rebreathers still remain the preserve of Technical Diving community.

Compatibility

All courses basic, advanced and technical are specific to each unit as their operation varies too much. So to dive a different unit you have to cross train with a Qualifier course.