Spare Air on deep but no deco dives??

[Colliam7]

No diver with his or her mental faculties intact is going to, in an out of air emergency at 100', going to 1) ascend at a "slow recommended rate which his half of what was taught in open water class" nor will the diver 2) sit at an optional safety stop 15' for 3', it's simply ridiculous to even consider that they would do such a thing in that situation.

This statement reflects an unfortunate, but not altogether uncommon, approach to diving - 'Uh, I guess I will rely on what might be barely enough to get to the surface uninjured, or at least alive, if I am lucky.' Dive that way if YOU wish, but don't present it to others as a reasonable approach, because it isn't.

Any diver with 'his or her mental faculties intact' should do exactly what is suggested in the article - ascend in a normal, controlled manner - instead of panicking and bolting to the surface. It is not 'ridiculous', it it prudent. In the (unlikely) event of an out of air emergency at depth, the whole point of having a redundant air supply, AND TRAINING TO USE IT PROPERLY, is to allow a diver to do just that - it is far better to be able to switch to an adequate redundant air source, and make a normal ascent including a safety stop, than to panic and make a (too rapid) rapid ascent. That too rapid ascent might get you to the surface alive, may even generate a BBC interview (Instructor bent after running out of air at 40m ), but may result in permanent disability. And, no amount of sympathy you might get from the article will change the reality of the injury.

The article also assumes an abnormally high SAC rate which probably does not apply to most divers.

Quite a few divers have a 'normal' SAC rate (or RMV if you wish) approximating 0.7 - 0.8 cfm, and to assume that the rate will increase by 50% in the face of of going OOA at 100 feet, is not at all unreasonable, or unexpected in the face of an acute catecholamine release associated with stress (such as might result from running out of air at 100ft).

The article also doesn't account for the fact that we can stretch a few remaining breaths of air because as we ascend the air in our lungs expands and we can exhale slowly to vent the increasing volume of air in our lungs.

Nor does it account for the fact that you may get 2-4 additional breaths from a rig that was empty at 100 feet, after you ascend to 15 feet, simply because of expansion of air in the system outside of the cylinder, and the change in ambient pressure. But, neither possibility changes the fact that it is far more reasonable to carry an adequate redundant air supply, so the diver doesn't have to depend on 'might' or 'may', and doesn't have to base their survival on the possibility that they can 'stretch a few remaining breaths'.

So once we remove the stupidity from the equation in the linked article, . . . 'Nuff said.

I agree, Nuff said. So, let's remove the stupidity from nonsensical assertions, and consider what is reasonable and prudent. 'Hope is not a strategy.' 'Prior Proper Planning and Practice Prevents Piss Poor Performance.' Divers who are competent, properly trained, and appropriately equipped will keep actually keep their mental faculties intact, and do just what the article suggests they should do.

For the OP, a Spare Air is a good, functional piece of equipment, when used for what it was designed for - shallow air crew egress under emergency conditions. It was not designed for, intended for, nor is it appropriate for, service as a redundant air supply for scuba diving. Is it 'better than nothing'? Possibly, unless carrying it creates a false sense of security, which undermines proper dive planning.

As others have suggested, you are better served by practicing good buddy skills.

 

[Bob DBF]

For the OP, a Spare Air is a good, functional piece of equipment, when used for what it was designed for - shallow air crew egress under emergency conditions.

I was corrected earlier, and figured I would pass this on instead of go look.

Spare Air - Info - Questions & Answers

I'D LIKE TO TELL YOU WHY I INVENTED SPARE AIR...

Larry Williamson, Inventor of Spare Air displays the HEED II and Spare Air back in 1986.

"One night I was lobster diving in the beautiful, clear cool waters off the coast of Catalina Island. After a short time, I realized I had failed to check my air supply. As I went to check it, I took a breath and discovered there wasn't one to be had. I panicked for a moment...got myself together and swam quickly toward the surface with the unnerving sense that it was too far away and I wouldn't make it! In this rush for the precious air far above at the surface, I began to black out...my only thought was... If I only had one more breath of air.

For days after this experience I would awake in a sweat during the night. Then I began to notice a recurring thought I had...it was the last words I recalled as I blacked out.... If only I had one more breath. Why was this coming back to me over and over again? Was I given a second chance to live for a reason? Then it dawned on me. There are others that didn't, don't or won't make it...There are others blacking out and never waking up... if they only had one more breath of air!

So the story ends with the present. SPARE AIR was born, and out of it my commitment to educate the world about preventable drowning and safe diving. I feel diving is safe, but it can and should be made safer. You, too, can join the quest and become part of the story of SPARE AIR."

Larry Williamson,
President, Submersible Systems, Inc.

 

[Colliam7]

I was corrected earlier, and figured I would pass this on instead of go look.

Spare Air - Info - Questions & Answers

Wow, I stand corrected! THANK YOU, Bob.

In that case, I may move to a harsher stance on Spare Air. IF they were designed for diving, they are simply a poor - inadequate, overpriced, needless complicated - equipment solution for their intended target indication. Far better, more effective and cost-efficient, solutions exist.

 

[yle]

So a 1 cu ft/min slightly panicked OOA diver at 99 feet (4 atm). That means between 99 feet and the surface with no safety stop, your average depth is 2atm. Therefore 2 cu ft/min average consumption...

Average is actually 2.5.

At depth: 4 atm ;

At surface: 1 atm

Average of 4 and 1: 2.5 I think you were using average of 4 and zero, but the pressure at the surface isn't zero.

(and we can use simple average because depth function is linear.)

 

[MaxBottomtime]

I have at least two major takeaways: First, I do agree and think that if I ran out of air at 120 feet or so and couldn't find my buddy or anyone else to grab their octo (I don't dive alone, always in a group), I would NOT be making a controlled ascent and I would NOT be doing a safety stop. I would drop my weights and shoot to the surface as fast as I could, recognizing that I'm likely to get bent. But better bent than DEAD, right?

I'm guessing an arterial gas embolism would probably kill you. I don't dive with any redundant gas but I would hope that I never drop my weights and shoot to the surface.

 

[rsingler]

Average is actually 2.5.

At depth: 4 atm ;

At surface: 1 atm

Average of 4 and 1: 2.5 I think you were using average of 4 and zero, but the pressure at the surface isn't zero.

(and we can use simple average because depth function is linear.)

Oops! You're right. Computing without thinking. Anyway, all the more reason why a Spare Air is a bad idea.
I edited the mistake in my post. Thanks!

 

[doctormike]

It's interesting to read the inventor's experience that inspired the Spare Air.

I would think that having that experience would make you say to yourself "Wow, it is LITERALLY the most important thing that I can do to ALWAYS be aware of my remaining tank pressure, at all times, no matter how many lobsters I see, no matter how beautiful the underwater scenery is, no matter what."

Instead, he came up with a gadget that says "Hey, I fixed the out of air problem with engineering! Just carry one of these things and running out of air isn't such a big deal so you can keep diving the way that you were before, since you now have a parachute."

Tech divers that don't have the option of CESA carry redundancy because they have to do a safe ascent, even in cases of catastrophic gear failure. Why wouldn't recreational divers want the same safety? Especially when diving deep enough so that a CESA just isn't safe, especially considering the amount of nitrogen loading you have even if you haven't gone over your NDL, and the big pressure swing from a deep dive.

 

[BDSC]

Instead, he came up with a gadget that says "Hey, I fixed the out of air problem with engineering! Just carry one of these things and running out of air isn't such a big deal so you can keep diving the way that you were before, since you now have a parachute."

The gadget never said that. You did. Don't be ridiculous.

 

[scubafanatic]

The often overlooked beauty of Spare Air is that's it's a modular system, cave divers could just string a bunch of them on a bandolier, for example.

 

[Compressor]

It's interesting to read the inventor's experience that inspired the Spare Air.

I would think that having that experience would make you say to yourself "Wow, it is LITERALLY the most important thing that I can do to ALWAYS be aware of my remaining tank pressure, at all times, no matter how many lobsters I see, no matter how beautiful the underwater scenery is, no matter what."

Instead, he came up with a gadget that says "Hey, I fixed the out of air problem with engineering! Just carry one of these things and running out of air isn't such a big deal so you can keep diving the way that you were before, since you now have a parachute."

Tech divers that don't have the option of CESA carry redundancy because they have to do a safe ascent, even in cases of catastrophic gear failure. Why wouldn't recreational divers want the same safety? Especially when diving deep enough so that a CESA just isn't safe, especially considering the amount of nitrogen loading you have even if you haven't gone over your NDL, and the big pressure swing from a deep dive.

The Doctor has spoken. Enough about this useless device.