I have never seen an Air 2 on a necklace. I have never considered that, primarily because I suppose, to dump air, I normally raise the air 2 and press the deflate button. If it was constrained to my neck, this option would be lost.
How do you normally dump air?
I agree with
@scubadada. I always use a butt/kidney dump 99.99% of the time. I'm in horizontal trim even on ascents to the surface until the last 3 ft, so it's not a problem. I picked up the habit from my tech instructor and using the xDeep tec 2.0 sidemount bcd. In the most streamlined position, the inflator sits on your chest so you can't dump it on ascent anyways.
In an air sharing, ascent scenario with a normal BC, a diver who does not use a pull dump, will need to locate the BC inflator (with their single free hand) and then raise it and press the deflate button to vent air.
With an Air 2, in an identical situation (with no alternative dump options being used or available) .. Then the diver has to grab the AIR 2 from their mouth, raise it, press the deflate button and simultaneously exhale for a duration of less than 4 seconds.
I really see VERY little difference in the two scenarios AND it could probably be effectively argued that it is easier to locate an AIR 2 (that is in your mouth) than a standard BC inflator that can be floating around somewhere. But I do completely agree, that a diver should practice ascending with their AIR 2 many, many times - until it becomes trivial.
I am surprised you reference poor performance with the AIr2. I recently started using an Atomic SS1 and I am somewhat embarrassed to say, it is tuned BETER than my primary second stage that is 30 years old- it breathes better at depth LOL. In any regard, the poor performance "issue" is addressed by tuning of the device.
Lastly, your comment about the sticky deflate button. That is 100% on point. It really seems to be a weakness in the design. It can make it difficult to orally inflate the BC, especially if you have weak hands or your strength is compromised by cold.
On the other hand, a Q-tip, vinegar and some silicone spray has kept my Air 2's working for years and years without replacing parts on the deflate mechanism.
TBH my opinion is that divers should not use their inflator to vent as they ascend PERIOD. If you ascend slowly and in control, this should never be a problem. You can vent with any dump you want and a quick pull of the butt/kidney/shoulder dump every 5-15 ft is a much easier and efficient. If it's a run away ascent, you probably trying to kick down anyways so you have to use your kidney or butt dump. I guess if an OOA diver is forcing you up and your in the upright position holding onto them and don't have a shoulder dump or can't pull your inflator hose, then you must use your inflator.
In regards to ascending and dumping with an AIR2, if you specifically have scubapro's AIR2, I'm assuming you can also pull dump the corrugated hose. When you pull the corrugated hose, it will dump via a spring like a OPV. The AIR2 itself won't be affected in anyway is what I believe. You can also breathe the wing air (make sure you keep it clean) as it deflates if you need to take a breathe. But I think this is over-complicating it. Just slowly ascend. Stop, dump some air via any dump or even pull the inflator out of your mouth and dump it for 1 or 2 quick presses. Then ascend and repeat until you hit the surface.
I agree with your experience with a properly maintained integrated octo. My SS1 has not ever gotten close to sticking either.
I don't think this is a question of what is adequate or not. Full disclosure, I have <100 dives and consider myself far from an expert. I appreciate everyone's opinion and input. With that said, I think everyone needs to decide for themselves an acceptable balance between safety, complexity, ease of use, number of potential failure points, what kind of diving they plan on doing etc. I'm on the fence as to what my opinion is. I think having one less hose one less thing around my chest area has merits. At the same time, I see value in having both my primary and backup being the same type of device and possibly even the same model. I can also see the value in not having to get proficient at trying to use the thing to breath and possibly control buoyancy. I think this is all an equation each person needs to solve for themselves.
For right now, I am leaning towards getting a duplicate reg as my backup and doing the necklace deal. Full redundancy, no learning curve, identical maintenance and features etc. But that's me. I plan on doing drysuit diving in my area and have not done the necklace setup. Has anyone found that having the backup in front of the chest to ever be an issue getting in the way of adjusting the drysuit with the supply valve, or bumping into your primary reg in your mouth etc? Thanks.
I agree there is less of a learning / training curve without an integrated OCTO. If you are learning new things like drysuit, I'd definitely would go your route. Get proficient with drysuit then add the next. If your in trim, your bungee reg will not be in the way of of your primary or drysuit inflator. If your vertical, I don't know if it will or not. The bungee should be adjusted tight and streamlined around your neck so it doesn't hang a lot. Furthermore, when you go to inflate your drysuit, you will hit your chest and run your hands to the inflator so it shouldn't be a real problem in practice.
So what happens if you have a stuck exhaust on the wing? In other words, you can't keep it inflated. I assume if it's the butt dump, you go head up to mitigate how fast the air can come out. When you get to the surface, do you just keep inflating it to counter act the leak to keep the kit from sinking until you can get out of the water? Hopefully, that isn't a stupid question. Do exhaust valves ever get stuck open? Or do they typically fail shut?
Your specific scenario is a damage on the bottom of the wing system (bladder or OPV). I rinse and check my OPVs every week so I never had an issue, but I've only had 200 dives.
If I was to have that specific issue, my goal would be to stop an uncontrolled descent and get to my buddy. If my buddy is above, I would be vertical and swim up and grab them. More likely, my buddy is 5-20 ft away at roughly the same depth. Then I would not be vertical, but horizontal with only much as an upright lean as I needed. Once you reach your buddy, there BCD would be used for both of you. You can choose to end the dive and drop your weights when your at the surface if you don't have enough positive buoyancy at the surface.
A more advanced skill, you would choose to pull out a DSMB or lift bag and use that as your BCD at depth. You can also do that once you reach the surface with your buddy if you need more positive buoyancy and don't want to dump your weights.
