Oceandvr:
Astute.
I don't think the philosophical discussion can be cleanly split in technical and recreational domains. Recreational divers have more freedom of movement and perhaps more haste when problems arise and technical divers are often more constricted in their freedom of movement but tend to be (as a group) a little more at ease dealing with such issues under water.
There are couple of things to consider:
1) where is my octopus? In that sense the AIR2 (et al) is a good solution because you always know where it is. There are other ways of ensuring that the octopus is always where they thought it was but either way it's a big improvement over the "back-there-somewhere" type of treatment many beginning divers seem to give to their octopus.
I should know. I was one of them. In 1985 I was nearly drowned by a rescue student with my "back-there-somewhere" octoups. Lesson number one (take if from me) is that if you don't know where your octupus is then you're asking for trouble.
This seems to be a big argument in favor of the AIR2 and it is.
2) Ease of donation. An AIR2 means that when it's raining s**t that *THAT* is the moment you need to take your regullator out of your mouth (if it isn't snatched) and fumble around for your secondary. The primary reg usually has a short hose and it means that when you could use a little room it isn't there. Moreover, most beginners aren't trained like this and rank beginners (the group most likely to encounter an OOA) who are the most ill at ease in the water really don't need confusion, extreme close proximity and extra steps when it's raining s**t. Swimming with this knotted up mess is creating two problems (craming, difficulty in swimming) and not even solving one.
3) Control over trim, buoyancy and ascent. This is where the AIR2 kind of sucks. Simply put, it complicates ascending under control. When it gets to the point that you need to use it, the next step is probably going to be to ascend. The AIR2 complicates that task.
So that's it. Octopus location....Ease of donation and control over ascent. On the first two the AIR2 scores at least as well as other options, but on the third point it creates a problem without solving any
For technical divers there is maybe one other issue, which is that you tend to have a little clutter on the left side anyway and having anything else on that side that's "in the way" is a bit of a pain. If you're poorly configured, your AIR2 could potentially become wedged between stage bottles or at the very least form a distraction. it's an issue because the inflator hose has to be long enough to service the AIR2 function, which would leave it dangling in the way or between your stages. So for technical divers, another solution was necessary.
The Hogarthian configuration sorts out this issue, plus it addresses the three points above adequately without creating new problems or solving problems that aren't there (like eliminating one hose.....which isn't an issue). The AIR2 doesn't do that. to me, Hogarthian is still optimal in 2005. You know where the octo is, donation is easy and control for both you and your buddy is as good as it's likely to get given the circumstances that make you want to share air.
Which begs the question, why isn't everyone going Hogarthian? Well, many divers are; either Hogarthian or DIR, which has its roots in the same soil. For tech divers this is a no-brainer, but for "recreational divers" the same 3 issues apply (where is the octo, ease of donation, control in an AAS situtation). The consequences of sloppy control etc aren't as severe for rec divers as they are for tek divers so you can get away with more but the issues are the same, none the less.
So why did we ever use the AIR2?
Ports.
My first reg had two LP ports. I had a primary reg, octopus, LP inflator and a drysuit. I was the first kid on my block with a drysuit that had a modern power inflator.... Lots of drysuits back then were still orally inflated and had an inflator hose like a BCD does today. Eliminating one hose meant having a *significantly* cleaner config and you could put your primary reg on it's *own* LP port. Part luxury and part necessity, especially in the cold waters in British Columbia, where I learned to dive.
This was the real forte of the AIR2 and needless to say this problem simply doesn't exist anymore.
So on point 1 above, the AIR2 is perhaps superior to a modern octopus but on points 2 and 3 it's not. Furthermore, alternatives such as the Hogarthian config address all three points adequately, which makes it, in my mind a better solution to the issues at hand.
R..
