Opinions on the Spare Air by SSI

[bpotkin]

I use my spare air with insta buddies and when diving in dense kelp. However I am very aware of its limitations.

 

[Thalassamania]

Matt, the problem is that the spare air provides confidence but not substance. Even 6cfm is woefully inadequate. If your dive really needs a backup (e.g., you're not comfortable making an ESE from the planned depth) then you need a real backup. I submit that a real backup is at least a 30 cfm bottle, I use a 40, with a wink and a nod to approximating the cavers' idea of 1/3 in 1/3 out and 1/3 for my buddy.

 

[DandyDon]

I do have 15,000+ dives at an average of about 8-10 feet deep. Freshwater commercial diver. 6-8 dives per day x 160+ days a year x 18 years. You do the calculations. All these dives were done on surface supplied air. I only have about 30 ocean dives. I tried it out in thirty feet of water today and I got over 5 minutes with it. I know it will be a third of this time at 90 feet or so. It really is just for an opportunity to get to my dive buddy in an emergency.

Ok, there is a big difference between your Surface Supplied Air shallow working dives and ocean diving - which I'm sure you know. Like I said, at least it's a 6 cf and not a 3 - a bit less than 1/10 of a standard 80.

Don't want to do an emergency ascent on it but would if i had to. Trust me, I'm no troll.... I find a large pony bottle to be bulky and cumbersome. I'm not interested in diving caves or deep inside wrecks. I'll go into the wheelhouse or look into the cargo hold from time to time but I never get too far inside. Just a preference of mine. Thanks for the input though.

Caves and wreck penetrations really require much more than a pony. True, my 19 CF is larger and heavier to pack, carry in luggage, carry onto the boat, dive with, exit with, etc. but it's a judgement call. You and your buddy should never be so far from each other that either of you need a SA to get together, but if you hit an emergency - use it as a CESA tool, and avoid overhead obstructions.

 

[vladimir]

I tried it out in thirty feet of water today and I got over 5 minutes with it. I know it will be a third of this time at 90 feet or so.

You breathed 1.2 (6/5) cu ft per minute at ~2 ATA. That's .6 cu ft per minute at the surface (1 ATA), and 2.4 cu ft per minute at 4 ATA (~100 feet). So at 4 ATA it would take you 2-1/2 minutes (6/2.4) to breathe 6 cu ft, or half the time, rather than a third.

 

[DevonDiver]

You breathed 1.2 (6/5) cu ft per minute at ~2 ATA. That's .6 cu ft per minute at the surface (1 ATA), and 2.4 cu ft per minute at 4 ATA (~100 feet). So at 4 ATA it would take you 2-1/2 minutes (6/2.4) to breathe 6 cu ft, or half the time, rather than a third.

...and that's assuming that the SAC doesn't elevate due to the stresses of having to implement an emergency ascent from depth.

SAC rates calculated at ease, rarely reflect the reality of air consumption during an incident. It's not uncommon, unless the diver is seriously as cool-as-a-cucumber, for SAC rate to increase by a factor of 4-10 times. How does that reflect on the gas duration of your chosen redundancy?

 

[darushin]

Personally, I would just spend the money that it costs on a true tank mounted pony bottle.

As pointed out by Devon Diver, that SAC rate you got doesn't factor in the increased breathing from the sudden stress of being out of air. Also a many divers who have done real OOA drills (ex. turning air off at depth) will tell you, the first thing you will do after you clear the reg is gasp a huge amount of air followed by a several rapid breaths of air. These gasps will cause your SAC to spike ten times your normal rate for several secs to a minute and given your limited backup may be the fatal flaw in your self rescue.

Another issue I have with these systems is deployment. When you are out of air your ability to handle task loading is greatly reduced and as such you may not be able to effectively deploy it before the lack of air causes panic and the issues that arise from it. With a tank mounted pony tied to a octo, it is right where you as a OW diver expect it and have trained to deploy it. It may not seem like much, but when OOA seconds count and simplicity rules.

Daru

 

[DivemasterDennis]

I'm with Thallassmania on this. I have never carried a "spare air" canister. If I was doing a cave dive or wreck penetration, I would go with at least a 30cf back up. But on recreational dives, I prefer to plan my dive, dive my plan, with a buddy who does the same, and monitor my air supply regularly.
DivemasterDennis

 

[flots am]

I have had several dreams where I have been at depth (80+ feet) and had an out of air emergency and my dive buddy is nowhere to be found.

I wrote a long post discussing SAC and ascent rates, and just deleted it. What you really need is training, practice and a good, reliable buddy.

SCUBA has little to do with commercial or surface supplied air diving, and your dream is caused by anxiety about diving with no support and a limited air supply. Your brain trying to tell you that you need a way to handle whatever is going to happen, and it's right.

Find a regular buddy and get some pool time in practicing air sharing and OOA ascents. You'll be much happier and safer.

flots.

 

[Spazzy]

Get a Luxfer AL40 and set it up as a stage.

 

[redacted]

You have already purchaed your spare air so, at this point, it is probably best to just focus on its capabilities and limitation. The biggest plus with a spare air is it travels fairly easily so you may be more likely to have it available at fly to destinations. But the capacity is so limited that you should not be carrying it with the idea that you have sufficient redundancy to make a normal safe ascent in an OOA situation.

While the 30 and 40 cf suggestions provide more than enough gas for complete redundancy, they just don't travel by air very easily so there may be situations where it is just too inconvenient. An intermediate sized tank (13/19) may be enough for many divers in most situations and they can fit within current luggage restrictions but still not as easily as a spare air.

I retired my spare air long ago in favor of smaller pony tanks. But I still feel that a spare is is much better than no air as long as you don't use it as an excuse to get stupid. I'm not sure what size tank is required to protect from stupid.