Rebreather questions

[john j]

Even though the closed circuit systems have redundant sensors and redundant electronics, they can fail. Certain types of failures can cause too much oxygen or too little oxygen in the breathing mixture. If the user dosesn't catch this and deal with the problem swiftly, it can be fatal. The training classes are intense and drill the student over and over on these problems, how to see them and what to do about it. My instructor drilled us ruthlessly during the class which is excatly what he should do. When a person dives on a closed circuit rebreather, he must frequently check the oxygen level by looking at the computer display. This is one way of making sure the oxygen level remains correct during the dive, but there are other ways too.

There is also a significant amount of set-up and calibration to do before the dive as well as more maintenance after the dive than you would be used to from open circuit. I always say that if you want to be the first one in the water, don't dive with a rebreather. What you get in return is extended bottom times and the ability to do multiple long dives without having to change tanks and get fills. Also no bubbles with a closed circuit system. I used to think so what? Now that I am used to not having bubbles I can really appreciate it.

There is a good book called "Simple Guide to Rebreather Diving" by Steve Barsky which I recommend. It explains a lot about semi closed and fully closed rebreathers and is at a level where the non-rebreather diver can understand.