A rebreather is SCUBA that allows you to re-breathe the exhaled gas you have already consumed, unlike open circuit scuba, you breathe directly from the cylinder and then vent all the gas into the surrounding atmosphere.
We only actually metabolise around 4% of the inspired oxygen, the balance is exhausted along with CO2. The rebreather captures the exhaled gas and re-uses it by removing the CO2 and re-circulating the oxygen, it also adds fresh gas to the system to keep it at a life sustaining level.
There are three different types of rebreather; SCR semi closed, CCR fully closed and oxygen rebreathers. The semi closed works on a principle of consistently adding fresh gas to the loop while re-using the exhaled gas. These units also vent a portion of the gas into the atmosphere, and even though this happens the gas supply lasts significantly longer than open circuit. A closed circuit rebreather is a fully closed unit that doesn’t vent any gas and re-circulates all the gas, and rather than constantly adding gas the unit monitors the level of oxygen in the unit and only adds oxygen at the time the unit needs it to maintain the preset or desired partial pressure of oxygen PPO2. An oxygen rebreather works on the same principle as CCR but the use of pure oxygen limits their use to 6m in depth.
The added benefits of rebreather diving include; bubble free quieter diving making them great for underwater research and photography, moister warmer breathing and easy buoyancy control.
Modern rebreathers are reliable and safe as long as the user fully understands the unit and its possible hazards. Each unit requires specific training and it is very important if you are considering diving with a rebreather that you seek training from an experienced rebreather instructor affiliated to a reputable rebreather centre. Once you start diving on a rebreather you many find it very difficult to come back to the dark ages of open circuit diving. |
