I would really advise against using nitrox below 40m in the Dolphin for two reasons.
1] Narcosis is a real problem.
2] Doing a loop flush [or even clearing a mask] with 30% in the tank at 60m will raise the pO2 of the mix up to 2.1 bar. What's more because of the amount of O2 in the loop in surface equivalent litres the pO2 will not drop that quickly-even if the supply is turned off.
Using a large [10L] tank and a fast flow rate will give a loop fO2 close to that of the tank fO2. The divers use of oxygen will also vary, so the supply fO2 has to be carefully considered. The supply fO2 also has to give a loop fO2 that can be breathed at all the depths the diver is considering using the rebreather at.
From my studies I think that the Dolphin can be used to 50m with a reasonable safety factor, and beyond this depth the diver's risk level increases considerably.
It must also be considered that the Dolphin scrubber was not designed for extremely deep diving, and the CO2 absorbsion abilities of the unit may not be adequate
Quote: (Originally Posted by
Humuhumu)
Hi,
Put a 28 to 30% Nitrox with a 40% injection and you're good for 60 meters :-) You don't need Trimix for that... (take care to have enough bail out with you: I use a 80 cft with air and limit my dive to 20 minutes botom time)
I know one diver who has tested it to 85 meters with Trimix... But I would say: go m-CCR if you want to do that !
Cheers
Bertrand
P.S.: take care, love you all :-)