A stupid question. I once met a rebreather diver who did not have his deco or advanced nitrox cert. He told me that shops would only fill his 13cu ft rebreather tank with O2 as he was not certed for anything else. For what ever reason he was in my open circuit advance nitrox/deco procedures class.
How does this normally work? The guy was not the brightest bulb so i declined to ask him any more.
Looking at some online descriptions I gather he had his MOD1. I am unsure why with the supposed hours he had on his unit, that he did not take a MOD 2 course instead of taking the OC adv nitrox/deco.
Take a quick step back. Have you ever noticed how us CCR Divers tell you to carefully select a CCR based on your requirements, unit specifc uniquenesses (quirks!), and yet theoretically there is only one golden training road to get to a CCR? I don't think so...
With the right instructor, student motorskills & intelligence, there's really no fundamental reason one even needs the mythical Adv. Nitrox/Deco "experience" on OC. Let's be honest, there's not exactly a seriously comprehensive CCR textbook, and much of every class is highly customized by the instructor to meet the student's needs for a CCR Class. Almost everyone attempting a CCR has a different diving resume from Zero to Hero. Hell, Richie Kohler wasn't ready to switch to a CCR until he saw enough people return alive to satisfy his skepticism - now he teaches on the big yellow box!
There is not any one instructor for all students, just as there is not any one CCR for any buyer, there is not one hard and fast progression path. Personally, I had no need for doubles and expensive fills - no thanks. I skipped Advanced Nitrox and Deco OC and went straight to the CCR for dives requiring those skills. NOW - That required a larger chunk of change & time than the $1,500 generally quoted for Mod 1.
If I were to desire to complete decompression dives on OC, realistically I should be standing in-line for the OC version of Advanced Nitrox and Deco. But...Frankly, for what it costs to run the rebreather versus doubles, you won't see me in line with a broken back with a set of Double 104s anytime soon. Ya Dig?
From a practical perspective, it's not unusual for CCR divers to run an Air Dilluient, however I choose to run 21/25 Trimix, which forces deco "early" as compared to Air, but deco seems to vanish from the handsets as I make my way to the surface. It generally costs me about $7.50 for a fill of 21/35 and I can get about four hours of diving out of it (if not more). Factoring Oxygen, I'm running a gas cost of under $4.00 an hour. I can't top an Aluminum 80 with Air for that price (unless I'm running the fill station). If you want a fair comparison, add in $7.50/hr for scrubber, and $0.75/hr for batteries.
Moral of the Story - Rebreather training is easily and commonly tailored to the CCR student. If you want to use more interesting Dil than Air, or be able to run a Deco Schedule, just ask your instructor. I'm quite sure with an additional day or two of training you'll be able to give you the knowledge you're "skipping" on Open Circuit.
Basically if you can calculate the MOD of a gas to make sure you don't exceed peak PO2 numbers for bailout or dil, you're going to be just fine for the basic class.
As for the hapless CCR diver. Take a look at a 60-foot dive on the Constant 1.2 PO2 Table. I don't have one handy, but it must take at least two hours to get into deco. Most boat drivers will be pretty pissed if you show up an hour after the recall time.
