JUST AS THE BRITISH SUB AQUA CLUB membership was in uproar over the potential banning of "hog-rigged" second stages in training, we decided to take a look at the humble octopus rig - the alternative air source (AAS) carried by divers for the benefit of others who might be out of air.
It was Bill Main, a contemporary cave-diver in the USA, who came up with the idea of running from his primary first stage a long hose that passed under the lamp-battery rigged at his right hip, across his chest and round the back of his neck to the second stage in his mouth.
Main's alternative second stage was kept on a short hose and necklace, ready to replace the long-hose version should this be needed by another cave-diver. He called it a Hogarthian rig (Hogarth is Bill's middle name, but it does sound better than a Mainian rig!).
Many conventional divers adopted this as being a convenient way to carry the two regulators. The system assumes that an out-of-air diver will take the second stage from the donor diver's mouth, knowing that it works and has the appropriate gas supply.
However, perhaps with an eye on modern litigation, the BSAC believed that this might pose too big a risk to an unsuspecting donor whose mouthpiece was unexpectedly removed while in use, triggering the recent debate.
So this month we look at alternative second stages on the assumption that they are not the one in the donor diver's mouth, and we take time out to see how easy and convenient they might be to use in a hurry.
One problem encountered with conventional alternative air sources is the small amount of attention they are given until the moment they are needed.
Jumping in with a loose second stage can cause the exhaust-port mushroom valve to get dislodged with some designs, and this will make it flood and be unusable should the time come.
Another common sight is to see a diver dragging a loose second stage across sandy or gravelly surfaces, again rendering it less than perfect. So an AAS needs to be stowed where it is safe from damage, can be instantly spotted by another diver, who might well be in a hurry, and be easily deployed and used.
For the purpose of official approval for sale in Europe (CE-marking), octopus rigs are intended to be used with their appropriate sibling first stage. However, all the models here were tested on a common first stage with a standard intermediate pressure rating. They are ranked in ascending price order.

A rock-solid dry breathe is just what you need if in distress, and this regulator provides it. Its hose was surprisingly flexible, allowing easy use when rigged from either side, although we felt it could have done with being just a little longer.
We found it nigh on impossible to dislodge the exhaust-port mushroom valve, but we considered the venturi plus/minus switch to be so ineffective as to be pointless.
The purge control was surprisingly aggressive, which might be regarded as inappropriate.

It's simple, it has no frills, and it works. What more could you ask for if you're the out-of-air diver on the receiving end of this octopus rig?
The exhaust-port mushroom valve looks a little flimsy, so check that it is located properly before and as soon as you are in the water, so that there are no disappointments when it comes to use.
We also suggest using an octopus retainer that plugs the mouthpiece to keep dirt out.
This octopus would be better deployed at the end of a longer hose.
Its purge proved a little gushy, giving all or nothing.

BUDDY AUTO AIR £83 with hose
A combined balanced regulator second stage and BC inflator, the latest Auto Air gives a good breathing performance and is now designed to be convenient for either diver (donor or recipient) to use. It has a unique direct-feed hose connection.
Users must become familiar with this kit, and should practise using it, because we encountered a problem with possible user-error.
To fill by mouth using the oral-inflation device for the BC, you press a grey panel, which looks rather like a regulator purge button.
The hazard comes from mistaking the real regulator purge button on the end of the device for the oral-inflation button during venting.
If this is used in error to try to vent the BC during a rescue, a reassuring supply of bubbles will be emitted, but the expanding gas within the BC will not be released, resulting in the possibility of an out-of-control ascent.
This is another reason to use the BC dump valves.
You need to treat this device as well as you do your normal regulator.

Cressi gets round the hose-from-the-right problem by means of extra length over that supplied with a primary second stage for its Ellipse Octopus.
It's a neat little unit, with a venturi switch to discourage unwanted free-flows, and proved straightforward to use. However, we found that the exhaust-port mushroom valve could easily be crinkled by poor handling or successive quick entries.
This led to water ingress and a wet breathe that would not be appreciated by an out-of-air diver.
The Ellipse would need to be checked for this before being donated.

Purpose-designed products are usually to be preferred, and this swivelling second stage is a good example. It can be used comfortably from any angle with no upside-down effect, and it can even be used with the hose coming from under the donor diver's arm.
The Octo Swiv has symmetrical dual- exhaust-port mushroom valves that are well protected from damage or being dislodged, and it can be used at any angle, but with the soft purge control on top. Press this hard at your own risk. It is very effective as a purge, but might surprise the unprepared diver.
This unit promises a very dry breathe. We were also rather taken by its magnetic retaining clip, which allows you simply to drag it off the donor's rig, although we did wonder how many out-of-gas divers would waste time trying to unclip it, simply because they were unfamiliar with it.

Trust the Japanese to get it right! This no-frills second stage can be supplied rigged right- or left-handed. Its purge is easy to use and very progressive.
The exhaust-port mushroom valve is well recessed to avoid it becoming dislodged, and the mouthpiece can be instantly replaced if needs be by means of its reusable retaining clip.
What more could you ask for?

Another compact regulator second stage that's actually bigger than it at first appears to be, the Neo comes complete with a venturi plus/minus and a valve-spring tension adjustment (BRA) that can ensure that it doesn't inadvertently lose any gas by being screwed down.
Both features could, however, add a little complication in an emergency.
The exhaust-port mushroom valve is so well protected that we could hardly see it, and there was nothing we could do to make the Neo leak, so a dry breathe is guaranteed.
It's best used hung from the left side but is not impossible to use from the right side of the donating diver. However, like some other conventional-style second stages, it would be better at the end of a longer hose.

Right- or left-side rigging? Scubapro gets round the problem with a second stage that can be supplied with its hose connected on either side. With simplicity of use in mind, the R295 has no switches or adjustments, and the purge has a long throw on the demand-valve lever. making it very progressive.
We liked the retaining clip supplied with the R295. This includes an attached plug that succeeds in keeping detritus out of the unit, and you can pull the second stage away from where it is clipped onto a BC D-ring without danger of pulling off its mouthpiece.
We did find that the exhaust-port mushroom valve could be dislodged simply by sucking on this regulator when its gas supply was turned off, and this did not auger well for a satisfactorily dry breathe. This feature could upset someone desperately heaving after a period without air.
The hose is slightly longer than for a regular second stage.

This is the Apeks answer to divers attempting to share air and getting in a tangle. It can be grabbed and used any way up, and the purge button falls readily to hand, because it is squeezed naturally when the second stage is held between thumb and fingers.
You can rig the Egress to the right or left (or at the end of a long hose).
It rotates easily, and we show it in conjunction with a super-flexible Apeks braided hose.
Despite trying to make it happen, we couldn't see how the exhaust-port mushroom valve could ever become dislodged, and highly recommend the Egress as an octopus solution.

This is the original combined alternative air source and BC direct-feed control in its fourth incarnation, and some would say it's the best.
The BC direct-feed button, oral-inflation control and regulator purge button are unmistakably different, and the Air 2 has been redesigned recently to be as sleek and compact as possible.
However, the length of the corrugated hose dictates that the donor must use it himself, and offer the second stage that is being breathed from (primary donate).
This adds to the danger of a surprise "take" by an out-of-air diver.
The mouthpiece is angled for best comfort, but it didn't give a fantastic breathe quality, suggesting that this product is intended for the no-stop leisure-dive situation in which participants can always progress directly to the surface should the need arise.
You need to look after the Air 2, rinsing it in fresh water after a sea dive, just as you would your normal regulator.

APEKS XTX 40 £144
This represents a number of similar conventional Apeks second stages that need to be rigged on the diver's left side, opposite the primary regulator hose, for best results. Here it will be less than useful to its owner, but can be deployed conveniently for another diver who faces him or her.
Otherwise it should be at the end of a long hose that is stowed away securely, but in such a way that it can be deployed in a moment.
The XTX 40 has a venturi control that can be set to the minus position to avoid unintentional free-flows when jumping in, and the exhaust diaphragm is well-protected from dislodging by a baffled exhaust-T.

Apeks now produces the world's most lightweight regulator - this thermopolymer second stage intended for use as an octopus in a characteristic yellow octopus colour scheme.
Because it is so small and neat, the Flight may appeal to many divers for use as an AAS. However, its fitting demands that it uses a special hose connection that may preclude it from use with anything other than the flexible braided hose with which it is supplied.
These flexible hoses certainly take the stress out of using a right-hand-rigged octopus with a diver facing the donor.
The Flight has a large, unmistakable purge button and a venturi plus/minus switch to discourage exponential free-flows. The exhaust-port mushroom valve looked well protected against dislodging, unlike the early version we had for DIVER Tests.

The whole idea of an alternative air source (AAS) is for you to donate some of your gas to another diver who might be out of air, so it follows that it must be rigged for easy access by another party in an emergency.
A purpose-designed clip will allow instant deployment, and keep detritus out when the AAS is not in use.

Most training agencies discourage the idea that an out-of-air diver simply helps himself, but the fact is that this is quite likely to happen. Someone who is desperate will not be inclined to stand on ceremony, so it's essential that the AAS is rigged is a place where it is prominent, easily identified and can be deployed without a hitch.

If you use an extra-long hose for your octopus and like to stow this under a couple of elastic straps on your tank, for example, you must ensure that it can be pulled free without snagging. A minority of divers prefer to breathe from a primary regulator on the end of a long hose that is looped around the body for convenience. They anticipate the OOA diver taking this from their mouth while they switch to a second regulator hung on a necklace under their chin.

A necklace is a good place to stow the alternative air source because, should another diver in a hurry grab the one in your mouth, you will know immediately where to find the replacement.

If you prefer a combined BC inflator and alternative air source, be aware that you will usually be donating your primary regulator and using the AAS yourself, so practise using it to ensure that there are no snags if and when you really need it.