Quote: (Originally Posted by carlthecat)
Hello all. This is my first post to this site. I am an experienced OC diver who is now getting into true OC tech diving (>130' & gas switches). Recently, I watched 2 shows, one on Discovery ("Deep Sea Detectives" - when they used rebreathers to get deep into a Cozumel cave system to determine how the Mayans got pottery and human sacrifices so far into the cave system) and the other was on Discovery HD ("Florida Underwater Caves" - when a man and his support team mapped some underwater caves in north Florida). On one (or both) of the shows, someone mentioned that the rebreather gave them somewhere between 10 to 13 hours of breathing gas. That leads to my first question:
1) Does/Can a rebreather give a diver 10-13 hours of breathing gas? If so, what is the maximum (ball park is ok)? Is the amount of breathing gas variable with depth like OC systems? Which rebreather models provide the highest breathing capacities?
Jeeez... my first question turned into 4...
So, after being intrigued, I came to rebreaterworld.com and read a bunch of the "new to rebreathers" material. During my reading, the author mentioned using 2 diluents on deep dives. This leads to my second (or 5th question):
2) How can a CCR diver change from one diluent to another in the middle of a dive? All the CCR rigs I have seen have one bottle for O2 and the other for the diluent. Do they change the dilutent bottle under water or is a 3rd bottle added to the rig?
After these 2 questions are answered, I will continue reading and learning about the interesting world of CCRs.
Thanks for all responses in kind,
Carl the Cat
For question 1 (or 1-4):
In theory yes but in practice I would say 4-6hours. It is easy to extend the gas range but the scrubber (remover of CO2) will eventually stop working.
CCR uses more gas when you go deeper. That is because you have to maintain a volume big enough for breathing. So going from 10m --> 20m you would add say 3-4 litres of gas (depends on your normal tidal volume).
2: The diver has a stage/sling tank that he connects to the breather and flushes the breathing loop with the new gas. The tank can also be mounted on the main rig.
Hope this helps a bit.
JH