Ok, after all these years of diving open circuit and shying away from the hastle and expense of diving nitrox...and after becoming very interested in eCCR's my wife and I finally got our basic nitrox cirtification this weekend. My wife has been quite hesitent to get into rebreathers because of the expense and bulk and complexity of gear. Taking the Nitrox class together has made the advantages of a rebreather much more vividly clear to both of us...and thus we are more likely to rationalize the expense and time investment (and ofcourse, it's a pre-rec for CCR).
If there is anyone reading this blog who is like me(or should i say, like i was), interested in rebreathers without nitrox experience but not fully convinced (or who has a wife/dive partner that is scowling at the cost) that rebreathers are the way to go then i suggest taking a nitrox course before going any further...the advantages of nitrox become very clear in the course, and so do it's limitation. As the value of Nitrox became more vivid during the course, even more so did the value of continuous gas blending on the fly to optimize the ratio of O2 and N at each depth to optimize maximum nitrogen displacement and reduce the limits set by O2 toxicity/MOD, as is done by a rebreather. Very quickly nitrox seemed like a rather arcane way of displacing nitrogen, the fixed ratio has significant draw backs like: You can't take advantage of the fact that all the way down to your max depth you can only be breathing a much leaner mix than those shallower depths would allow and What if you want to go deeper than you planned...donditions are better than expected, you see something you want to explore below the MOD...oops, can't do it on nitrox! You've had to choose a specific mix of O2 (the lowest common denominator) based on your maximum planned depth). Or lets say your in a down welling that suddenly picks up and you go below the MOD without choice and your huffing against strong current, or for any reason end up below your MOD?...could be end of story on Nitrox!
Not to say that nitrox isn't worth it... it's more like the advantages seem to be ten fold on a rebreather. And that fill of nitrox goes up mostly in bubbles with each breath, only a small fraction of it's oxygen ever being utilized.
for us, it's pretty likely that fixed ratio Nitrox will be our gas of choice for only a short time...as a gateway to rebreather diving.