In fairness to all, I do not think that is what is actually being said.So as a new diver not yet certified it sounds like if I mistakenly find myself at say 80 ft and ooa BUT I have a 3cf spare air BUT not a 19cf minimum pony, I might as well just take in a big gulp of sea water and be done with it.
If I was OOA at 80ft, I would definitely rather have a Spare Air (1.7 OR 3 CF) than nothing. I imagine most of the posters in this thread would say the same thing. The more important point being made, and being directed at any diver who is serious about planning for a redundant gas supply, is that there are probably several better options than a 3CF Spare Air.
In order to have a Spare Air handy at 80 ft if I go OOA, I have to plan for that - I have to acquire one, make sure it has gas in it, make sure I have it with me on the dive, etc. If I am going to plan those steps, why not plan to have a redundant air supply that allows me to make a safe, controlled ascent from 80 ft?
LP sells 3 CF Spare Airs for ~$165. They sell 19 CF pony cylinders for less than that (~$140). Of course you have to then buy a reg, so either approach is not without cost, and I do not mean to suggest that a 'real' pony is less expensive than a Spare Air. But, if I am going to the trouble to plan to have a Spare Air, wouldn't it make more sense to plan to have a redundant gas supply that is actually useful.
Let's use 100 ft as a more practical example. If I breath ~ 0.7 CFM at the surface, I am going to be breathing ~2.8 CFM at 100 ft. Frankly, if I were to go OOA at that point, my consumption would increase substantially, to at least 4 CFM, if not more (provided, of course that I had redundant gas to consume ). So, if I go OOA at 100 ft, I would prefer to have an immediately accessible gas supply, that allows me to get to the surface in a reasonable manner. I want enough gas to cover 1 minute at 100 ft to sort out the issue (you don't necessarily immediately understand what is happening when you first suck on a vacuum) and deploy my redundant gas supply - that's ~ 4 CF+ right there. I want enough gas to make a controlled ascent - let's say 50 ft/m max - to the surface. Using an average depth of 50 ft for calculating consumption, that's an additional ~ 5 CF I would even prefer to have enough gas to make a safety stop as well. So, at a minimum, I want to plan for ~10 CF of redundant gas, and in reality more than that. Could I blow and go from 100 ft and get to the surface alive on a 3 CF Spare Air? Quite possibly. But, if I am going to go to the trouble to plan for redundancy, I am going to anticipate needing at least a 13 CF pony (if that is my chosen approach to redundancy) - and frankly, I want more.
I don't laugh at Spare Airs, or divers carrying them. At least, a diver carrying one has given thought to redundancy. Kudos to them. If someone asks me what I would recommend as a minimum redundant air source for recreational diving, I usually say a 19 CF pony, and I encourage them to even consider a 30, or better yet consider learning to use doubles - backmount or sidemount. I do not notice a 30 cf bottle clipped on my left side. But, I am used to that and maybe others might find it cumbersome.
So, the point is NOT that Spare Airs are 'bad', or useless, or something to be laughed at. Rather, they simply do not reflect realistic planning for redundancy. (I suspect that a few posters are also of the opinion that having that Spare Air might even give a diver a false sense of security. But, that's another issue.)
Certainly, the best plan is one in which you do not go OOA to begin with, and that is actually my preferred approach.
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