Reef Oasis Dive Club

Rebreather für alle

What is a rebreather?

The primary difference between rebreathers and open-circuit units is that rebreathers reuse some or all of the gas you exhale. There are two basic types of rebreathers: closed-circuit rebreathers (CCRs) and semi-closed rebreathers (SCRs).

Advantages of Rebreathers ?

Efficiency advantages

The main advantage of the rebreather over open circuit breathing equipment is economical use of gas. With open circuit scuba, the entire breath is expelled into the surrounding water when the diver exhales. A breath inhaled from an open circuit scuba system whose cylinders are filled with ordinary air is about 21% oxygen.

When that breath is exhaled back into the surrounding environment, it has an oxygen level in the range of 15 to 16% when the diver is at atmospheric pressure. This leaves the available oxygen utilization at about 25%; the remaining 75% is lost. As the remaining 75% of the breathing gas (mostly nitrogen) is inert, the diver on open-circuit scuba only uses about 5% of his cylinders' contents.

At depth, the advantage of a rebreather is even more marked. The diver's metabolic rate is independent of ambient pressure , and thus the oxygen consumption rate does not change with depth.

The production of carbon dioxide does not change either since it also depends on the metabolic rate. This is a marked difference from open circuit where the amount of gas consumed increases as depth increases since the density of the inhaled gas increases with pressure, and the volume of a breath remains almost unchanged.

Feasibility advantages

Long or deep dives using open circuit scuba equipment may not be feasible as there are limits to the number and weight of diving cylinders the diver can carry. The economy of gas consumption is also useful when the gas mix being breathed contains expensive gases, such as helium. In normal use at constant depth, only oxygen is consumed: small volumes of inert gases are lost during any one dive, due mainly to venting of the gas on ascent. For example, a closed circuit rebreather diver effectively does not use up any diluent gas after reaching the full depth of the dive. On ascent, no diluent is added, however most of the gas in the loop is lost. A very small amount of trimix could therefore last for many dives. It is not uncommon for a 3 litre diluent cylinder to last for eight 40 m dives.

Training

The PADI Rebreather and Advanced Rebreather Diver courses use Type R units to introduce divers to rebreather diving within recreational dive limits. Type R rebreathers are electronically controlled and provide a back up for all the major systems and simplify training and use.

All rebreathers used during PADI courses must be third-party tested and manufacturers must ensure they meet a comprehensive list of requirements.

Because each rebreather model is different, you will need to qualify on each rebreather model. However, once you are qualified you will not need to repeat the entire course to earn your certification with a different Type R rebreather model. The PADI Rebreather Qualifier focuses on the knowledge and skills needed to use a different Type R rebreather model.