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[Enlarge image] Decompression, stage, pony and argon cylinders: usage and rigging   Author: Matti Anttila. Copying etc. prohibited without prior written permission by the author. Comments: matti@antti.la. Last update 5.3.2002. In case the reader of this page has comments, questions etc, I'm happy to receive them by e-mail or web form.

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Contents:

The purpose of this page is to represent few aspects regarding the use of stage, decompression, argon and pony cylinders. This is NOT a self study guide for anyone not trained to dive with cylinders mentioned in this text. Always get proper training! See also: 8. Training.

Decompression cylinder is a gas cylinder which contains your decompression gas. Usually it is 5 to 10 liter cylinder and made of aluminium, containing enriched air (EANx) or oxygen. You must know nitrox and CNS tables and methods prior using decompression cylinders. Take some course to learn right methods and skills. Decompression cylinder is usually made of aluminium and range from about 4 to 10 litres. Some links: http://www.gasdiving.co.uk/pages/misc/kit/stages.htm http://www.diverite.com/resource/stage/ http://www.gue.com/equipment/equip-anatomy.shtml

Decompression cylinder : aluminium, 7 ltr 200 bar, oxygen clean and dedicated to only oxygen fills

Stage cylinders increase the amount of gas that a diver can carry on a dive. Stage cylinders usually look very similar than decompression cylinders, but the purpose is a bit different. Take a look at: http://www.divernet.com/technol/techqa1000.htm An example: A dive begins, and our example diver breathes first from his stage cylinder. After 1/3rd of stage is gone, he switches to his back gas. Then he'll breathe 1/3rd of his back gas, turns, breaths again 1/3rd of back gas (now remaining 1/3rd), swithces to stage, breathes 1/3rd and surface. Diver has now 1/3rd remaining in the stage cylinder, and in the back gas cylinders. Note that this is just an example and there might be zillions of opinions/methods to do this! However, you should definitely get proper training before doing this!

Stage cylinder . Aluminium, 10 ltr 200 bar.

A pony bottle is a little independent air source, almost like a smaller version of your primary scuba gear (tank and regulator). In an out-of-air situation one can switch to the alternative air source instead that one should take his/her buddy's alternative air source. There are some advantages, but also disadantages (for example: price, mass, service etc.). Take a look at: http://www.webspan.net/~hummer/pony.html http://www.gue.com/equipment/tanks2.shtml

Pony attached to the right side of back cylinder.

Small argon cylinders are used to fill dry suit with argon for increased thermal insulation. Argon has about 1.5 times better insulation than air has, and it is used when diving in cold water or when using a gas with high thermal conductivity such as a trimix or heliox in one's back cylinders. Inflating one's dry suit with a trimix (or other helium based mixture) can produce a large degree of body cooling due to helium's high thermal conductivity. A dangerous reduction of body temperature can easily result from the use of helium-based mixtures for suit inflation and divers should avoid this practice. Additionally there is a limited risk of counter-diffusion when immersed in a gas of lower density than one's breathing medium. Dry suit argon bottles usually range from about one to four litres. The regulator contains usually only a small "button type" pressure gauge and an over pressure valve. Welding argon is usually not suitable for suit inflation, because it may contain some (around 15% in the UK) carbon dioxide (CO2), which then has the potential to form carbonic acid in combination with your sweat, irratating your skin after a while (although it may not be very noticable after just one dive), and apparently will rot undersuits after a season or so.

Argon cylinder (aluminium 1,5 ltr * 200 bar).

If the cylinder contains rich oxygen mix (EAN40 or more), it should be oxygen cleaned. Some sources say that you should have oxygen clean equipment if you are dealing any mixture with oxygen more than air (EAN22 or more). What ever proper rule you follow, the point is to have the cylinder free of possible contaminants that could lead to fire or explosion when cylinder is introduced with high oxygen content. The cylinder should have clearly marked MOD (maximum operating depth), your name, and possibly the content (ie. "OXYGEN") with big letters. Take a look at: http://www.gue.com/equipment/tanks-5.shtml. You'll need also a carrying strap (stage strap) with two snaps and a stage clamp or cam band to secure it to the bottom of the cylinder, and a hose retainer. Don't do metal-metal connections between snaps and cylinder (use rope/line that is possible to cut with diving knife)! This page shows you "suicide clipses", which you should definitely avoid: http://www.gue.com/equipment/attachment.shtml. Off course, you'll get more information on any technical diving course! See also: 8. Training.

Image above: equipment needed to rig the deco cylinder. Image on right: stage/deco strap.

Proper entry: "Giant steps" etc. are not very recommended to a diver with very heavy load of decompression cylinders and tech gear. If possible, get in to water first and let your support team handle cylinders to you or then place them to the water (and secure them) before you go (see image).	Image above: Not like this...	Image above: .. but place the stages/decos first to the water (and secure them), and don them in the water.
Deco/stage placement: Is is common to place deco/stage cylinders to your left side. This method allows a diver more flexibility as one arm is unencumbered. The diver may more easily use a scooter and often finds that they can work through smaller areas with stage bottles intact. It is common to place the first bottle to be dropped on the outside where it is more easily reached. If neither bottle is to be dropped the richer mixture is usually placed on the inside or closer to the hip as it is the last to be used. If another bottle is needed one can clip another bottle to a small d-ring on the light canister. See also: http://www.gue.com/equipment/jj-hogarth.shtml	Image above: Definitely not like this...	Image above: the right way to start the dive.

Training agencies for diving with deco- and/or stage cylinders:

GUE (http://www.gue.com):
For example: Tech Diver 1-3 courses.

IANTD (http://www.iantd.com):
Advanced Nitrox Diver, Technical Diver, Normoxic Trimix Diver and Trimix Diver courses.

DSAT (http://www.padi.com):
Tec Deep Diver course.

NAUI

TDI

etc.