Argon Set Up

Posted on 21. Jan, 2004 by Greg Mossfeldt in Gear

Argon set ups

This dive tip is an attempt to address most of them in a document that will be easily searched for henceforth.

One of the most commonly debated questions is the benefit of using argon over air. The heat transmissivity of argon is theoretically about 2/3's that of air. In practice, the benefit will probably be less than that. Choosing good drysuit undergarments, such as heavy thinsulate, will do much more for warmth than will adding an argon system to a mediocre undersuit. You should only really consider adding an argon system to your rig if you are already diving a leak-free suit with good undergarments and are still getting cold. If you have good a good undersuit, then argon will provide some benefit, but in any case you must purge the suit with it a few times, articulating your body to work the gas into the fibers prior to the dive for it to be of use. When gas mixes using helium are employed, argon becomes a necessity. The heat transmissivity of helium is over five times that of air, and using a helium based mix for drysuit inflation will rapidly cool the diver.

Eric Maiken wrote an article with a much more thorough explanation of why argon is the gas of choice for drysuit inflation. It is available at the the following link:

One final point with respect to the gas itself: Provided you are using straight argon and not any sort of welding blend or other gas combination (for the reasons explained in the above article), any grade is suitable. You will not feel any difference between the stuff used for welding (99% pure), or the 99.99999% pure research grades. Save your money for the stuff that matters.

Once you make the decision to use an argon bottle, here are a few things to consider:

What size and type of bottle to use?

For short dives or straight down and up profiles (most wreck dives), a 6 cubic foot bottle is a very clean, compact package, and is easily mounted at the waist location (explained in further detail below). A disadvantage to the 6 cu. ft. cylinder is that it doesn't hold a great deal of gas, and if you want to thoroughly purge your suit several times with argon prior to entering the water, you may need a second argon tank just for this purpose in order to have enough gas for the dive.

The other commonly used argon tank is the low pressure (2015 psi) AL14. This holds more than enough gas to do several recreational dives with, or is sufficient for longer and deeper profiles. The major advantage of this cylinder is the low working pressure, which means for the home mixers that it can develop its rated capacity from a straight transfill, without necessitating a booster pump to get the pressure you need. This cylinder is typically used in the back tank-mount position (again, explained in further detail below), but it can be waist mounted when wreck diving or diving tight cave passages.

The argon bottle needs to be connected to your suit, but must not interfere with stage bottles or the effective operation of any other gear. This necessitates mounting it either to the back tanks or on the waist strap. When mounted on the waist, this is accomplished by a belt loop which is large enough to pass over a knife sheath on the same belt (so the bottle can be removed at any time). The bottle should sit as high as possible without interfering with movement of your left arm, and should be held back to your backplate with a loop of bungie cord. In more open passages, or when using the large bottle, it is typically mounted to the back tanks with velcro straps that can be undone underwater by the diver, without assistance. The bottle should ideally be as low as possible, to place it within the turbulence zone already created by your body and back tank(s), minimizing any additional drag created. In either mounting position, the bottle is mounted inverted to enable you to keep it in a low drag position, but still be able to control gas delivery manually by manipulating the tank valve. As there is no second stage on an argon system, there is no inherent overpressure relief mechanism. An intermediate pressure failure at the first stage would result in either a blown hose or damaged suit inflator, and so a separate overpressure valve (OPV) must be installed on the first stage to provide this function. I place the OPV in a port on the inside of the inflator hose so that it will not be damaged if banged. The hose has a strain relief on it, as with all other hoses, and the tank valve is 300 bar DIN with the rubber Sherwood knob for maximum impact resistance. The argon bottle must also be mounted in such fashion as to enable you to remove it without assistance in the event that you get "keyed" (where you can pass a restriction in one direction but not the other), or "ratcheted" (where you can move forwards but not backwards) in a confined space. It must also not have any non-standard fitting, so that the BC inflator and argon inflators can serve either purpose if necessary, and also so that you can donate argon to a buddy for egress on profiles that require adding gas to exit. The intermediate pressure on the argon reg needs to be dropped dramatically. This is so you have time to deal with a runaway inflator before you risk a loss of buoyancy control, and also so you can hold the inflator down without adding more gas than your descent rate requires. I typically set mine from 80 to 90 psi. Some regulators will not allow this drastic an adjustment without custom parts. If you can't do this, set it as low as possible with the reg you are using. The bottle needs to be mounted on the left side for two reasons: the first is that with the valve orifice and reg in the forward (protected) position, the handwheel falls to the left. The second is that if you ever need to reach behind you to clear an entanglement or manipulate your environment at all, you can reach around a light canister on the right side, or the argon bottle on the left, but not both. The hose should be the minimum length necessary to reach the inflator fitting on your suit, without straining regardless of your body position, once all the other factors have been addressed. Some divers like to avoid swivel drysuit inflators, due to the extra failure point, but I prefer them because they tend to alleviate stress at the inflator location as you move your body around, and also because, should I choose to dive with back inflation instead of argon, the inflator hose can assume a more natural position as it feeds from the left post.

These issues need to be carefully considered. In overhead diving (real or virtual ceiling), the argon regulator is the most critical regulator on a dive, as it is the only one for which there is no backup.

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