Rebreather Component 1: Oxygen Tank
Oxygen is needed for any form of life on this planet, so it is no wonder that it ranks as one of the first rebreather components. An oxygen clean tank is located on the right side of the rebreather. The amount of pure oxygen in the tank depends on the duration of the dive, but for the most part a typical rebreather will have a 2 or 3 litre tank filled to at least 140 bar of pressure. Such a tank can supply hours worth of oxygen to a rebreather diver since consumption values are based on oxygen metabolism rather than a respiratory minute volume (RMV). The rebreather either electronically adds oxygen to the loop as the diver metabolizes it via an oxygen solenoid or the diver can manually add oxygen with a manual oxygen inject valve.
Rebreather Component 2: Diluent Tank
As a basic nitrox diver you learn that a partial pressure of oxygen (PPO2) should not exceed 1.4 bar during the working phase of your dive. Minimal exposure to a PPO2 of 1.6 is acceptable during the decompression phase of a dive. A rebreather system with only oxygen can therefore only dive to 6 meters before exceeding these rules. The job of the diluent is to dilute the oxygen to lower the PPO2 at depths greater than 6 meters. The most common diluent used for rebreathers is air. For deeper dives beyond the recreational range varying mixes of trimix are used for the diluent. The diluent is commonly chosen based on reducing the amount of narcosis at depth and acceptable PPO2 levels. All mixed gas rebreathers will have a diluent as one of their rebreather components.
Check back later for more information about rebreather components in future blogs…