Buddy:
You're two courses away from 10/50... you've not even finished recreational trimix yet. You have a LOT to worry about before you worry about hypoxic mixes. Several years of other things to worry about actually. You have loads of normoxic mix diving ahead of you first. And 10/50 is lazy mans gas. When you need 10% you need the other number to be 70.
But to think WAY ahead for you:
The rEvo has as one of it's two main achilles heels the lack of an ADV isolator. The way you would handle it on a Meg would be to let the loop come to 0.7 on the surface prebreathe, shut the ADV isolator, get to 20 feet using only 02 on the 02 bypass valve, and then opening up the ADV. Your ADV is then closed at the bottom (unless you are flushing) and you never have diluent available to your mouth again. Bear in mind that the Meg SOP is for the ADV Isolator to be CLOSED unless you are descending or flushing and that the rEvo way is for the ADV to always be open.
On the rEvo, you cannot isolate the ADV. You can turn off the cylinder but you then lose the wings. One way to remediate this is to run a short hose along the left side of the scrubber to a 2 port Omniswivel port, continue one line to your wings and then add another hose over your shoulder to an isolator, then back down over your shoulder to the plug-in point at the bottom of the rig. You "turn the corner" at the lower point by using yet another Omniswivel 3 port fitting, with the top two ports used for the inlet-with-slider hose and the other for the return to the rig hose. While you are at it you might as well add a QD to the bottom of it and then you can plug in an offboard diluent there and feed the rig with it after isolating the slider feeding onboard gas to the block.
If you do this, you mimic a Meg save for one thing: A Meg has a third add valve, the mixed gas bypass valve. So even with the ADV isolated you can have another diluent plugged into your mixed gas bypass valve. You can mimic that on the rEvo by adding a manual bypass valve with the input into the port on the exhaust valve. That offboard gas add point (which can be used for 02 as well) is a requirement for ANDI mixed gas training, so you will be doing that mod before we dive. Putting in the ADV isolator hosing on the rEvo is not a factory option although it probably should be), so I am on a teeter-totter regarding what I like to see technnically and what is a factory setup which is what I am obligated to teach. Leave it at that.
None of this deals with a BOV either...
You can abandon all of the above and do gas switching from one diluent to another using the system you already are playing with, if you carry appropriate mixes in the appropriate spots. For ocean diving I suggest breathable mix in your onboard so you can have OC when swimming to/from the ladder (assuming that you drop off your stages in the water). Cave diving is a different thing... there is no surface swim. So everything needs to be balanced against environment.
The bottom line is that there are MANY ways to do it safely, but IMHO you need to add some hoses to a rEvo to do it safely. On the Meg... it comes ready to use out of the box.
Now:
Your open circuit options for that first 20 feet can change according to the way you are rigged and the environment, but you will not be carrying 10/50 in a stage bottle. We can discuss all of it on your Level 4 Mix Course but you will not be using hypoxic mix until you are in a level 5 course. For now your best friend will be 18/45 and then 15/55 after that. 10/70 is a long way off.
JJ guys: I found the lack of an ADV isolator very puzzling on the JJ. And the clearances there make the normal Omniswivel shutoff too big to fit. I stuck a 6 inch regulator hose on the ADV, the slider to that, and then shortened the ADV feed hose. Anyone else think about this?
Dave
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