Should I get a Spare Air?

[SeaFlea]

Hello everyone. I've read several threads concerning the Spare Air system and while my investigation was prompted by my thoughts of buying one, I would like to ask a question.

I thought the idea behind Spare Air was to give a few breaths to allow a person, in the event of a regulator failure, to ascend to the surface. Is this not correct? Many posters feel that the 3.0 cuft of air isn't enough. Enough for what I ask. I'm sure we would like to include a safety stop on the way up but isn't getting to the surface the end goal? I think 20 or 25 breaths is adequate for a normal ascent from 75 ft or so. One reason I ask is after investigating the price of a 13 or 20 cuft bottle, a regulator, and a decent strapping system, I find the cost to be more than twice the cost of a Spare Air. For 200 usd I can get a new 3.0 cuft SA. At 50-80 ft thats good for at least 20 breaths.

Are my facts right? Is a redundant air supply for a recreational diver that seldom exceeds 80 ft (photographer) overkill? I dive with a ScubaPro Mk25/s600 and have it serviced every year.

Thx for your thoughts.

 

[DA Aquamaster]

I am not a spare air fan. But the problem is not so much with the Spare Air device itself but rather with divers who get one and then develop a false sense of confidence and security that gets them even deeper into unmanageable situations.

The same can be said about small pony bottles, or for that matter large pony bottles and isolator manifolded doubles. Regardless of what you use for redundancy you need to be very aware of the limitations of the system. Spare Air takes a lot of well deserved heat because it's limitations are substantial and the potential for exceeding them is great.

Spare Air is better than nothing only if you stay within the Spare Air's limited useful envelope. There are better systems on the market and a 6 cu ft pony, while widely regarded as being indaequate for deep diving, still offers twice the air of a Spare Air. Spare Air may work for you on shallw dives, but I get worried when I read that it should be good for at least 20 breathes at 50-80 ft. Don't count on it. Especially in an emergency.

For the same $200 US you can buy a 19-30 cu ft pony online and a well maintained quality used regulator such as a Scubapro Mk 3 High Performance or Mk 2 R190.

 

[Drew Sailbum]

but approximately half of the Spare Air units that I have seen divers with on our boats in the Caymans have had some sort of failure.

Most commonly, I see that the unit leaks air at a significant rate requiring refilling between dives. Any air source that cannot hold pressure for an hour or so is one I won't rely upon.

I have also seen failures of the "pressure gauge" mechanism and the fill mechanism.


Edit:
Crud. This was supposed to be a reply to the thread on Spare Air, not a new thread. Any Regulator magic?

 

[ScoobieDooo]

I'd go an AL19... I use an AL40!

If you calculate your SAC rate you'd probably be surprised to find that a Spare Air won't supply nearly enough air in a panicked situation, increased respiratory/heart rate, increased physical exertion, a safety stop, etc. and still allow for any margin of safety.

I've had two experienced tech divers / instructors send me directions on calculating my SAC rate and after looking at depths, scenarios, etc. it was pretty clear that a Spare Air is a joke...

Sure, at most recreational depths (less than 120 ft) any dive is generally a no-deco dive as long as BT's are not exceeded and you could probably ascend w/o doing your safety stop and not get bent - however, why risk that?

For the price of a spare air you can get a AL19 and a simple non-adjustable 2nd reg for close to the price of a Spare Air.

 

[Scuba_Vixen]

Living in a resort location, I see a number of spare airs attatched to vacation divers' bc's, and a near equal number on the workbenchs at the LDS's. They seem like a great idea, but something failed in the execution. Known reliability issues with something you may stake your life on, scares h*ll outta me. You can get a MK2/R190 and a 19cft pony for just a little more. Add a ReefScuba X bracket (mounts on the bc cam band) and a mini spg (bring it over your left shoulder with your bc inflator) and you'll have solid reliability and enough redundant air for almost any emergency you'll see in rec diving profiles. Just hang the second stage in the usual octo location and safer diving.

Darlene

 

[sheck33]

how about a buddy?

 

[ScoobieDooo]

Buddy?

Thats great in theory but I have seen that fail several times in real life situations to depend on...

 

[MikeFerrara]

Put a dozen spare air's on an ammo belt and where them accross the chest for easy access.

Plan your dive. Manage your gas. If you feel the need for redundancy use it. How about an h-valve? That covers you for regulator failure. If you just want extra gas in case you run out...just dont run out.

In my experience many who feel the need for a spare air or even a pony bottle are doing dive that are a little much for their equipment and skill level and they know it but they won't admit it. I don't like going to 100 ft without redundancy so I don't do it without my doubles.

I all you need is enough air to get to the surface then just go to the surface sooner. If you think there might be a problem that delays your ascent then what you need is enough gas to allow you to solve the problem. A spair air or small pony may not do that.

It's just more crap to hang off you.

 

[ScoobieDooo]

Dealing with twin 98's might not be that fun either though Mike...

 

[Epinephelus]

It's just too much work to reconstruct this to fit photography per se, but you can do that in your mind. Here is my post from another thread re: Spare Air...
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Breakin' out my handy dandy calculator... average no-stress RMV of oh, shall we say .6 CFM.... If I'm spearing at uh, 120' or so... and something interferes with my ability to monitor my gas (as Zen says) "such as seeing a fish and going after it, pursuing it after your strike, and often in hunting you will push your air management to the limits because you have not taken any fish or perhaps you see some action toward the the end of your dive, also, you don't follow a rigid dive plan when you are hunting, because you are hunting and exploring, and you often don't know where it's going to take you," so that I just can't pay adequate attention to my gas and run out and so, decide to calmly make my way to the surface with my "redundant" gas supply in my Spare Air.... Hmmm...
At 30 fpm (we are still going to adhere to normal ascent rates, aren't we? I mean, would we actually plan to put ourselves in extremis and have to make a rapid, high stress ascent? Nooooooo, not us) we'll need 240 seconds, that is, four minutes, to make our ascent. At an average depth of 60 feet during that ascent, that means that we'll calmly use about 7 CF of gas, only four more than I have in my Spare Air (oh, I have a double spare air, so I'm only one CF shy... hooray!).
But let's be realistic. In the scenario where the situation actually causes me to be so inattentive as to run out of gas, there's likely more going on than when I'm breathing at .6 CFM. In fact, from experience I know that in a typical engagement (not a balls-to-the-wall fight, mind you, but a typical spearing, from spear release to subduing and stringing the fish) my air consumption goes up to about 1.2 - 1.5 CFM, and on a balls-to-the-wall engagement it zips up to over 3CFM - and at that rate, even if I make a 120 FPM ascent from 120' (one minute) I'll burn 6CF and increase my chances of DCS by God knows how much - but too much.
For me, then, I require some other option than a spare air. My personal plan is to never allow *any* fish to interfere with my gas plan. When I was young and immortal I'd say to myself "you can shave it a little more" but I have learned a little patience over the years. There'll be another fish another day, and if dinner's in jeopardy there's always Winn Dixie.
Because there can be emergencies that cause gas to go away quickly other than inattention, I do carry independent gas when spearing solo, be it doubles or a pony. If a pony, my personal minimum size is 30CF, which actually will, unlike a spare air, allow a safe ascent, complete with safety stop, in the event of a catastrophic gas loss.
If your diving style allows for the possibilities you've expressed, and therefore a chance that you'll inadvertantly run out of gas unexpectedly because of the way you choose to dive, almost anything other than a Spare Air would be better. Even a good old fashioned "J" valve will give you 8 CF!
But don't just take my word for it. The next time you're out spearing, just after stringing a fish, take your reg out of your mouth and plug your Spare Air in, and make an ascent. If you're happy with the results, great - but I expect you'll find out that we old farts ain't just blowin' smoke when we advise against a Spare Air as a viable "redundant" gas source for a spearo.
E.