@TravelGas suggest you have a look at the threads under tech diving about the helium situation. There are a number of them from this year.
EDIT: there are other reasons to go CCR. Warmer/more moist breathing gas so you stay warmer and have less of a cotton mouth, longer dives, better gas logistics, etc.
EDIT: there are other reasons to go CCR. Warmer/more moist breathing gas so you stay warmer and have less of a cotton mouth, longer dives, better gas logistics, etc.