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woodcarver
Contributor
That is a good point. Of course, it may not be universally applicable. Personally, I have both handled one (actually multiple), AND I have used one, actually several, for training purposes. And, I recommend against the use of a SA as a REDUNDANT AIR SOURCE. It simply is not adequate to serve in that capacity. Even 6 cf of air, and certainly 3 cf of air in the configuration primarily available until recently, at depths equal to or greater than 90 ft, is insufficient to make an 'normal' ascent to the surface in case of a catastrophic gas failure. That is reality.
You are certainly welcome to use one, exclusively. That is your choice. The very good news is, catastrophic - abrupt, complete - gas supply failure is exceedingly uncommon . Even though 'Insufficient breathing gas' was cited as the most common 'mechanism of injury' for scuba fatalities reported in US and Canadian divers - accounting for 15% of the incidents - in the 2018 DAN Annual Report (https://www.diversalertnetwork.org/medical/report/AnnualDivingReport-2018Edition.pdf)- which was based on 2016 data, there is no evidence that these incidents were solely the result of catastrophic gas supply failure.
Actually, that is not correct. What IT boils down to is whether a diver is serious about carrying a REDUNDANT gas supply. If they are, then a SA is simply inappropriate. If they are NOT serious about that, the issue of what to carry is moot. Carry a Spare Air. Plan to breathe the air from your BCD. Carry a rabbit's foot. Whatever. It makes no difference.woodcarver:
I couldn't have said it better myself. That is exactly the issue. That is exactly the VALID objection to use of the SA system. And, the fact that the volume has been doubled, to 6cf, is inconsequential. As you so appropriately stated, it is still a 'small tank'. Whether it travels well, or not, is of no consequence. How easily it deploys is irrelevant. Whether it functions as a REDUNDANT gas supply IS the issue.woodcarver:
You are quite correct. Of course it doesn't. But, that was not the OP's question in this thread (70-90 feet was specifically mentioned). If I am carrying a gas supply that is intended to be REDUNDANT, it must function appropriately throughout the dive, not just for part of it. Moreover, if I am at 30 feet, I can reasonably do a CESA - and, yes, I have also 'handled' that procedure, and actually used it once. But, if I am at 90 feet, and my buddy is not accessible, a CESA is really not a viable option, and I am left with an emergency buoyant ascent - a very unappealing option. And, a gas supply that will not get me to the surface without an excessively rapid ascent is little better. Notably, after 'Insufficient breathing gas', the next two most common 'mechanisms' of injury cited in the DAN Report were 'Rapid Ascent', and 'Panic'. You go out of air at 90 feet. You don't have enough gas in you 'redundant' supply to get to the surface using a normal, controlled ascent. You panic, you ascend too fast.woodcarver:
If a piece of gear is not going to meet the need for which it is being carried, don't carry it. Having a regulator on my primary gas supply that will only function from the surface down to 60 feet is of no value to me if I plan to dive to 120 feet. Having a REDUNDANT gas supply that is only adequate to 30 feet, is of no value if I plan to dive to 90 feet. It doesn't mean that the particular redundant supply is 'BAD", rather it means that it simply cannot serve the function for which it is being used.
Several posters in this thread have questioned the appropriateness of the discussion in a 'Basic' forum. The point has been made that we should be emphasizing good buddy technique, good diving procedures. I am quite comfortable with that. But, the OP's question was directed toward what he might carry as a back-up for dives to 70-90 feet. So, let's address that issue.
I have no particular bias for or against a Spare Air, per se. But, I do not delude myself into thinking that is can serve as a REDUNDANT air supply at 90 feet. In the 1934 movie, The Scarlet Pimpernel, there was a very insightful comment voiced by the main character, Sir Percival Blakeney (played by Leslie Howard): 'and nothing in the world is so bad as something which is, "not so bad".' A Spare Air is 'not so bad'. It MAY even be 'better than nothing' - at 30 feet, maybe at 60 feet. But don't say that it is an appropriate REDUNDANT gas supply for deeper dives. It is not.
Hmmm... since you quoted my post, I assume this was directed at me. Which is strange, because my post did not "denigrate" Spare Air, and did not "advise against it." And to top it off, I have handled and used a Spare Air (although not in an emergency situation.)
My post simply stated that the previous poster brought up a "good point" (ok, THAT was my opinion... but it was an opinion on the issue presented by the other poster), and then made a simple factual statement: that "Unless its secured to the diver somehow, there is a non-zero chance of dropping the thing before it gets in the diver's mouth."
Not sure where you're seeing denigration. I have seen Spare Airs with retention devices, but I don't believe (unless it's a new addition) that they come standard with such devices. If they are marketed to new divers, and new divers expect the SA to be ready to use out of the box, and there is no bungee retention device, it would be useful to advise new divers to consider what could happen (mishandling the SA?) when they go to use the device in an emergency situation.
There is no denigration of SA happening in this thread. If anything, there is a rational discussion of its limitations and how those limitations are noticeably absent in the marketing of the device to inexperienced divers. Unfortunately, it's our job to do the best we can to make up for this deficiency and provide new divers with full disclosure so they can make the best decisions to minimize the risk to themselves and those they dive with. I apologize, on behalf of everyone in this thread, if that offends you.
In defense of Spare Air... the bungee discussion reminded me of something: a situation for which Spare Air is better than a pony.
Until recently, I was on a dive team at the local aquarium for several years. The deepest exhibit there is 28 feet, and most of our time was spent at maybe half that. The dive locker there has a rack of the mini (i.e. 1.7 cu ft) Spare Airs, and it was required that we take one with us on all dives (and they were bungeed to our BCDs.).
Why? Because it kept OSHA happy (or at least it kept them less unhappy.) It was in the regulations, so we did it. I'm sure this is the reason they bought the 1.7's instead of the 3.0's also; the regs didn't specify the size of the cylinder.
We were required to do "training" on them also, just so paperwork was complete. The training was to make an ascent from 28 feet breathing on the SA. It worked... you can get a couple minutes of air from one of those when you're at an average depth of 14 feet.
Until recently, I was on a dive team at the local aquarium for several years. The deepest exhibit there is 28 feet, and most of our time was spent at maybe half that. The dive locker there has a rack of the mini (i.e. 1.7 cu ft) Spare Airs, and it was required that we take one with us on all dives (and they were bungeed to our BCDs.).
Why? Because it kept OSHA happy (or at least it kept them less unhappy.) It was in the regulations, so we did it. I'm sure this is the reason they bought the 1.7's instead of the 3.0's also; the regs didn't specify the size of the cylinder.
We were required to do "training" on them also, just so paperwork was complete. The training was to make an ascent from 28 feet breathing on the SA. It worked... you can get a couple minutes of air from one of those when you're at an average depth of 14 feet.
woodcarver
Contributor
No need to apologize, no offense here.
I was quoting you in regards to the question of whether the SA could be dropped. As I have not seen one that didn't come with the coiled lanyard, it seemed appropriate to point out they are designed to be tethered to the diver. The other quoted was in line with someone recommending against, yet had never used one.
And as discussions of the SA go, this has certainly been one of the more civil. A good thing as this is in the basic arena.
I'll step up here and admit I was one of the suckers who bought one. This was before I understood about min gas and all (one reason why I teach min gas at the open water level - so my students don't waste their money on garbage).
Fortunately I lost it on a dive in Australia and never attempted to use it in an actual emergency. For new divers who don't train with it, I do believe that there is a possibility that they will fumble with it and drain it fast. The level of training in this industry is quite low. My rectal-cranial condition was starting to be treated before I took fundies, but that course provided me the last bit of lubricant necessary to free me of that ailment.
Though I will say, anyone that understands ascent rate, gas consumption under stress, doesn't need to actually have held one to know its a bad idea.
Interesting... maybe the bungee tether is now packaged with new SA's. If so, that pretty much wipes out the risk of dropping it. I haven't seen a new one, in a box, in a while.
Blackcrusader
Contributor
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