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The Advantages of a SCR Over a CCR Rebreather

A rebreather is a device SCUBA divers use that captures a diver's exhaled carbon dioxide and converts it back into oxygen, which the diver can then breathe. The system that accomplishes this is called a "breathing loop." The process by which the carbon dioxide is cleansed and converted to oxygen is called "scrubbing." Rebreathers come in a variety of designs, including closed-circuit rebreathers (CCR) and semi-closed rebreathers (SCR).

CCR
- CCR stands for closed circuit rebreather. A CCR system is electronically controlled by at least three oxygen sensors. The sensors constantly monitor the oxygen content of the breathing loop. An on-board comuter makes adjustments. The system also includes dials thatmonitored by the diver, can adjust the oxygen content manually.
SCR
- SCR stands for semi-closed rebreather. It is the oldest rebreather system and is less complex than the closed-circuit system in that it lacks the computer system that CCR systems have. With a SCR system, there is a 20% loss of gas from the breathing loop, which is why it is called a semi-closed system. The excess gas must escape the system, which creates bubbles under water. This gas loss does not occur when using a CCR system.
Advantages of Rebreathers
- Rebreathers have several distinct advantages over more traditional SCUBA systems. One of the most important advantages, especially for CCR systems, is its silence. Since the CCR is a closed system and recycles oxygen, there is no loss of gas. Therefore, no air bubbles are created while exhaling, which could potentially alarm marine life. Rebreathers also offer much longer dive times than other SCUBA systems. With a rebreather, a diver can remain submerged for hours regardless of tank size.
Advantages of SCR
- The primary advantage of a semi-closed circuit rebreather is in its simplicity. An on-board computer largely automates the oxygen content of a CCR system. This means that the system is a lot more complex than the completely manual SCR system. The computer and advanced electronics can malfunction or fail. The SCR system puts the diver in complete control of the system's oxygen level. This way, the diver doesn't have to rely on the computer system or be concerned with its possible failure.

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