Alternate Air Sources - split from Minimalistic

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Alternate Air Sources - split from Minimalistic

Postby ChuckyBob » Tue Sep 25, 2012 12:55 am

MikeB wrote:Yes - I understand that would be the plan. But sharing gas off a short primary hose, even in a recreational setting is far from ideal. The divers are forced to be pretty much on top of each other, which can result in even higher stress levels (adding to those of the current OOG situation). In this case, the diver would need to donate from the mouth to the OOG diver. I think this is great, but is would be better to do it with a hose of a suitable length.

Simple fix to that is to use a 7ft hose on your primary. I should have mentioned that. Its one of those instances where more is less! More hose but routed nicely so less mess! :lol:



The donating diver then has to switch onto the combined inflator/octi. I don't really have any personal experience with these, apart from seeing a few incidents caused by them (Greg do you remember that incident with a RB diver at the cowshed a while back? Think Phil was diving with him at the time...). I don't really understand why you would remove a potential third regulator from your arsenal.


I dont recall any incident where the octi inflater was to blame ( maybe I miss understand your statement).
How many regulators do you need? There comes a point where they just get in the way and cause more issues than what they can solve.
eg. I dont have OC access to my on board O2. I could add a 2nd stage but where would it go? I could bungy it around my neck. But the hose routing to it would be a right pain. It would also get in the way when I remove the loop from my mouth. At best it may give me access to 600l of O2 but more than likely it will only be 300l. At worst the regulator could free flow and I could lose all that O2.
Having a second gas source can sometimes add a sense of security that isn't warranted. Most of these devises when used by recreational divers are positioned in a way that they are not easily accessible, and they are often poorly maintained.

Dont forget not filled properly.
Do there spare airs have gauges? I think some have button gauges but they are far from accurate. Can you turn them off or do they stay on all the time ( and slowly leak out). Unless you are filling it before every dive then how do you know whats in it?
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Alternate air

Postby divepirate » Tue Sep 25, 2012 8:53 am

Dont forget not filled properly.
Do there spare airs have gauges? I think some have button gauges but they are far from accurate. Can you turn them off or do they stay on all the time ( and slowly leak out). Unless you are filling it before every dive then how do you know whats in it?


The button guage is not letting you know content, but it does say full or not.
I find the best thing when using it is to do a 30 sec pre-dive topup as part of getting ready to dive, then you know it's full.

I carry the spare air under my right arm where DIR would recommend a light canister.
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Re: Minimalistic.

Postby MikeB » Wed Sep 26, 2012 11:50 am

Simple fix to that is to use a 7ft hose on your primary


Definitely agree!

I dont recall any incident where the octi inflater was to blame ( maybe I miss understand your statement)

Hmm - maybe you weren't there that weekend. The octi inflator certainly wasn't the cause (I believe it was CO2 buildup in the modified loop), but it certainly added to the "incident pit" when his buddies tried to help.

How many regulators do you need? There comes a point where they just get in the way and cause more issues than what they can solve.

For a conventional OC setup - Two, with a standard inflator as well. I think your setup is outside of the realms of this discussion.

Unless you are filling it before every dive then how do you know whats in it?


Firmly agree; they are the worst idea ever...
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Re: Minimalistic.

Postby divemaster » Wed Sep 26, 2012 12:26 pm

Mike would you say it is better to dive without a second air (backup source) than to to have a device that will allow you to perform a slower ascent to the surface.

Bear in mind that this setup is for non-tech diving.

I know guys that use the spare air an d they wouldn't dive without one.
In contrast to divers that leave their pony in the garage because they find them too clumsy for recreational diving.

All of the people that I know using these devices perform a reg test charge, (I.e. breathe test, then balance fill) before diving.
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Re: Minimalistic.

Postby ChuckyBob » Wed Sep 26, 2012 12:28 pm

Ah, I think you may have been referring to a CO2 hit on a inspo diver.

There were at least contributing factors to that.
1. Mouth piece was fitted up side down on BOV. It was one of those comfy bite ones where there is a piece that is supposed to run across the roof of your mouth. It didnt.
2. The loop was twisted and in certain positions restricted the gas flow leading to an increase WOB.
From what I recall he did have a SP octi inflater and the issue was that the other diver wasn't sure which was the inflate button. It was never used to breath off in this situation.
I am pretty sure he has now removed it and most people will agree they are not suitable for that level of diving.

But for simple single tank rec diving ( and also where there is a pony tank slung) I think they are fine.
In over 500 dives I have never had to donate air. In reality it is not a common occurrence. And if it is then there are probably steps that need to be taken to reduce it.
So use of a octi inflater that helps eliminate clutter on every dive isnt a bad choice IMHO. The only real down side I see is that when you do need to use it you are a little restricted in your head movement due to the hoses coming off the octi inflater. But considering you will only be using it for a max of 7 minutes ( 40 meters ascend @ 10merters per minute + 3 for a safety stop) its not that big of a deal.

Of course I am sure we both agree that by simply using a 7ft hose and a necklaced octi ( instead of a octi dragged behind or having its poor hose folded in two and pushed into a D ring) is probably a better solution over all. But lets face it, the vast majority of divers will not do this. They get taught bad habits during OW and carry them with them for the rest of their diving.
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Re: Minimalistic.

Postby ChuckyBob » Wed Sep 26, 2012 12:44 pm

divemaster wrote:Mike would you say it is better to dive without a second air (backup source) than to to have a device that will allow you to perform a slower ascent to the surface.

Bear in mind that this setup is for non-tech diving.

I know guys that use the spare air an d they wouldn't dive without one.
In contrast to divers that leave their pony in the garage because they find them too clumsy for recreational diving.

All of the people that I know using these devices perform a reg test charge, (I.e. breathe test, then balance fill) before diving.


I know this was directed at Mike but I will give my opinion for what its worth.
Given the choice of using a spare air or not I would choose not. I think they give a false sense of security. The available gas in them is too limited and a small free flow incident on one could go un noticed and you could end up depending on something that isnt of use.

If someone finds a pony too clumsy I'd suggest it simply isnt set up properly. For recreational diving I'd say a 3 litre tank is bare minimum (Make that 2.7 litre since I have 2 for sale! :twisted: ) But a 30cf ( 4.5l) or 40cf( 5.7l) is probably a wiser investment if looking at doing any deco diving in the future. Oh and if you use a 80cf tank instead you have defacto doubles and then you are not limited in your dive time by your SAC rate.

How many of you out there with Spare Airs have tried doing an ascent with them?
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Re: Minimalistic.

Postby binklebonk » Wed Sep 26, 2012 1:02 pm

The problem I see with the "spare air" is this.

We have a tendency, once we adopt a device to mitigate risk, to increase the risk of the activity to the point whereby the mitigating steps are no longer valid. A bit like how we tend to adjust our level of spending to match a pay rise.

The amount you are likely to increase your risk if you are using a "spare air" will probably be greater than the device can mitigate.

A suitably sized pony or better buddy protocols are preferable IMHO.
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Re: Alternate Air Sources - split from Minimalistic

Postby divepirate » Wed Sep 26, 2012 1:08 pm

Good explanation.
There is no mitigation, and useage of these devices needs to be in circumstances where dependance is not required.

I would like to hear from someone that is teaching the 'independant' diver spectialty, to see what their take on this is.
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Re: Alternate Air Sources - split from Minimalistic

Postby binklebonk » Wed Sep 26, 2012 1:10 pm

Andy teaches independent diving but I don't think he's on here much at all nowadays.
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Re: Alternate Air Sources - split from Minimalistic

Postby binklebonk » Wed Sep 26, 2012 1:17 pm

This is a very good read, ignore that the subject is avalanches as it is relevant for all risky activities.

http://avtrainingadmin.org/pubs/McCammonHTraps.pdf
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Re: Minimalistic.

Postby MikeB » Wed Sep 26, 2012 1:26 pm

Good discussion.

ChuckyBob wrote:
Of course I am sure we both agree that by simply using a 7ft hose and a necklaced octi ( instead of a octi dragged behind or having its poor hose folded in two and pushed into a D ring) is probably a better solution over all. But lets face it, the vast majority of divers will not do this. They get taught bad habits during OW and carry them with them for the rest of their diving.


Yip - I think the 7 foot hose and necklaced backup is ideal for open water (and of course more challenging environments). People just need to have their eyes opened to the idea, and be shown how beneficial it is. Poor open water habits are unfortunate, but inevitable in the current diluted state of diver training. I for one, would really like to see the quality of training lifted (in NZ and internationally).

I agree with bink about people increasing the risk of their dives because they think the spare air will save them. This is one of the many reasons I am against them.

For recreational (depth<30m), "non deco" diving I don't think an alternative air source is necessary if you are diving with a suitable team obey conservative gas conservation rules such as "Minimum Gas".
Last edited by MikeB on Wed Sep 26, 2012 1:29 pm, edited 1 time in total.
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Re: Minimalistic.

Postby MikeB » Wed Sep 26, 2012 1:28 pm

divemaster wrote:Mike would you say it is better to dive without a second air (backup source) than to to have a device that will allow you to perform a slower ascent to the surface.


Sorry I don't really understand what you are asking here...

I would rather not have a "spare air" and instead have properly trained buddy.
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Re: Alternate Air Sources - split from Minimalistic

Postby ChuckyBob » Wed Sep 26, 2012 1:44 pm

divepirate wrote:
I would like to hear from someone that is teaching the 'independant' diver spectialty, to see what their take on this is.


I think Andy would ask you to do the maths :twisted:.
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