Spare Air on deep but no deco dives??

[EireDiver606]

This article proves that a 3 cubic foot Spare Air is enough gas to get a diver to the surface from 100' which is opposite of what it says at the bottom of the article which contains two statements that are just plain nonsensical.

1) For a three-minute safety stop, you’ll need another 2 cubic feet of air.

2) it should take you about 3 minutes to get to the surface if you maintain a nice controlled ascent rate of 30 feet per minute. Yes, it’s twice as slow as what you probably learned when you took your open water class, but for extra safety, 30 feet per minute is recommended.

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.

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

So once we remove the stupidity from the equation in the linked article, and revisit the final statement in the article: which is "You need 8.5 cubic fee of air" we can subtract the 2 cubic feet calculated for the safety stop and half the remainder due to the faster ascent rate and you get almost exactly the contents of the large model of spare air which is 3 cubic feet. Even if we assume an excessive SAC rate and don't account for releasing the gas slowly to conserve it. 'Nuff said.

Sorry

Stating incorrect facts over and over does not make them correct....

The Spare Air was NOT originally made for pilots in the military. It was originally introduced for recreational diving, and introduced for military use AFTER it was seen in the civilian use.

sorry I meant to say they were invented for scuba but now that’s the military use them for.
My apologies.

 

[wetb4igetinthewater]

sorry I meant to say they were invented for scuba but now that’s the military use them for.
My apologies.

Don't be. It isn't relevant. They are unfit for scuba, but found an appropriate niche with the military/aviation.

This was invented for scuba. I hope we can all agree it is a bad idea: Snorkelator® – Easy Dive

 

[tursiops]

The one minute at 100 feet

Time to work the numbers. 100 ft is 4 atm. A unstressed breathing rate is typically 0.7 cuft.min; stressed will double or triple. The Spare Air has 3 cuft, not all of which is available (you can't breath a tank down below the regulator's intermediate pressure). So, how long will the Spare Air last at 100 ft while one is sorting out or looking for a buddy?

The whole discussion reminds me of the guy who was arguing how many jumps it would take to get across the chasm. The argument that a few extra breaths is better than none is like trying to jump the chasm in several jumps.

 

[Sevenrider860]

Divers are being taught by some agencies that if they really screw up and let their buddy get too far away and they are out of air they are to make a CESA or an emergency buoyant ascent. Throw all the math around you want, but if the choice is no air or a few more breaths, they chose a few more breaths. The average diver is not traveling around with a 19 cu ft cylinder. But I see a lot with Spare Air.

Why is it so hard to understand that marketing a small, travel friendly item that gives a person a few more breaths in those two out of air circumstances is attractive to some divers? Nobody is saying it is a safe alternative to a larger backup gas supply or proper buddy awareness...but they feel it is a better alternative to nothing.

You made a joke about drowning, but my question was serious. How many deaths is anybody aware when a Spare Air was used on the emergency ascent? They certainly have a number of testimonials where the result was survival. We can all look at the circumstances and find where the user screwed up and did not do things correctly...but they ran out of air, used a Spare Air, and survived.

This really seems like another AIR2, Split Fin, and Jacket BCD discussion...

 

[wetb4igetinthewater]

Divers are being taught by some agencies that if they really screw up and let their buddy get too far away and they are out of air they are to make a CESA or an emergency buoyant ascent. Throw all the math around you want, but if the choice is no air or a few more breaths, they chose a few more breaths. The average diver is not traveling around with a 19 cu ft cylinder. But I see a lot with Spare Air.

Why is it so hard to understand that marketing a small, travel friendly item that gives a person a few more breaths in those two out of air circumstances is attractive to some divers? Nobody is saying it is a safe alternative to a larger backup gas supply or proper buddy awareness...but they feel it is a better alternative to nothing.

You made a joke about drowning, but my question was serious. How many deaths is anybody aware when a Spare Air was used on the emergency ascent? They certainly have a number of testimonials where the result was survival. We can all look at the circumstances and find where the user screwed up and did not do things correctly...but they ran out of air, used a Spare Air, and survived.

This really seems like another AIR2, Split Fin, and Jacket BCD discussion...

Do you think we’ll get actual data on how many people died when using a SpareAir when going to deep and not paying attention to their SPG and dive buddies?

I won’t hold my breath. We hardly ever get detailed information on diving deaths and you think that asking that question is realistic?

The fact that many people buy these means nothing. This device gives people a false sense of security.

While people are trained to do a CESA, a lot of divers still drown. Sure one guy did it from 200 feet, but many don’t make it from shallower depths.

As an instructor, I’d rather teach my students to plan appropriately. For a solo diver course, they get to do some math to prove the point. I’d like to teach it in open water, but then I’d run into interference theory.

CESA is when there is nothing else and it is for poorly trained and equipped divers.

 

[caruso]

If you are carrying a redundant gas supply, why not carry one that will for certain let you do your normal safe ascent? And if you don't think that the normal safe ascent is necessary, why do a safety stop at all?"

Safety stops add an additional measure of safety and perhaps, over the course of many years of diving may save a diver from a case of the bends if they regularly practice safety stops after dives to depths of say 50' or more. That does not mean one blown safety stop in the case of an OOA emergency which may or may not occur once in a divers life will cause the bends.

So when you fly with it, you have to empty it and then have it VIPed when you get there? You don't do yearly regulator service on it? That's not cheap.

Spare Airs are refilled using an adapter on the main tank no need to VIP or have it filled at a dive shop. Yearly regulator service is overkill.

Why is the spare air less expensive? I mean, it's $200. You can put together a cheap used pony bottle and reg for less than that. Maybe you can get Spare Airs used, I don't know. But not that much of a difference.

You are probably right that the initial cost of a Spare Air is the same or even more than a used pony bottle setup. I don't think I posted otherwise.

I'm getting confused here, you seem to be going back and forth. You either feel you need a redundant gas supply or you don't. All I'm saying is if you feel you need a redundant gas supply, get one that will let you do your normal, safe ascent. Also, get one that can't empty in less than six seconds at depth if it accidentally gets purged or free flows.

Me? Speaking for myself- I used a Spare Air for several years then decided I'd be better served with a 19cf pony bottle which I carry on all dives to depth. My posts on this thread are in the context of this thread as it pertains to the original poster.

 

[caruso]

Do you think we’ll get actual data on how many people died when using a SpareAir when going to deep and not paying attention to their SPG and dive buddies?

I won’t hold my breath. .

Cute! If the pun was intended of course.

 

[doctormike]

Divers are being taught by some agencies that if they really screw up and let their buddy get too far away and they are out of air they are to make a CESA or an emergency buoyant ascent. Throw all the math around you want, but if the choice is no air or a few more breaths, they chose a few more breaths.

But that's NOT the choice. That's a straw man argument. You are not sitting at depth with no air and deciding between the Spare Air and no gas at all. You are making the choice ahead of time to have a redundant gas supply adequate for a normal safe ascent, or not having that. Throw all the anecdotes around that you want, but that's the question here.

The choice is - once you decide that you would like to have a redundant gas supply - do you want an adequate one or an inadequate one? Yeah, you can come up with scenarios where a couple of breaths from a Spare Air make a difference, but the point is why not decide ahead of time to have the right tool for the job.

 

[wetb4igetinthewater]

Cute! If the pun was intended of course.

I’ll admit it wasn’t but I’m laughing now

Let’s not forget for what the acronym Boyle’s stands!

 

[doctormike]

Why is it so hard to understand that marketing a small, travel friendly item that gives a person a few more breaths in those two out of air circumstances is attractive to some divers? Nobody is saying it is a safe alternative to a larger backup gas supply or proper buddy awareness...but they feel it is a better alternative to nothing.

Exactly. You are 100% right that it is attractive to some divers, and that they feel that it is better than nothing. It clearly sells. We are not discussing marketing here. We are talking about safe diving practices. The fact that many divers think that this is a safe diving practice doesn't carry much weight in that discussion.