Wreck diving is an amazing pastime; but unless you’re diving only shallow wrecks, you probably wish that you could spend more time on the wreck itself and less on deco. Here is a short guide to mixed gases for wreck diving and deeper commercial diving; if you decide to take a technical dive course, you’ll learn even more.
Why Breathe Mixed Gases?
While decompression stops are a necessary part of diving, allowing gases that have saturated a diver’s tissues to be release slowly, using mixed gases can help prevent oxygen toxicity and improve decompression. In addition, using “non-air” gas mixtures can help to prevent nitrogen narcosis. As a recreational diver trained in the proper use of mixed gases, you’ll find that wreck diving is much more enjoyable. A word of caution – breathing the wrong mix can lead to fatal accidents. Be sure your mixed gases come from a reliable source.
Types of Mixed Gas
Common gases used for diving range from standard air, which is actually 21% Oxygen and 78% Nitrogen, plus another 1% of trace gases. Standard air is good for dives up to forty meters, although using mixed gas will extend bottom time. Other common gas mixes for diving include:
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Nitrox – This is an enriched mixed gas which contains more than 21% oxygen. Using Nitrox helps decrease the risk of decompression sickness and accelerates deco. A common misperception is that Nitrox can be used on deep dives; in reality, 32% can be used at a maximum suggested depth of 34 meters, and 36% at a maximum suggested depth of 29 meters.
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Trimix – A blend of oxygen, nitrogen, and helium, often used on deep dives, this mixture reduces the risk for oxygen toxicity as well as the risk of nitrogen narcosis. A variety of blends are designed for use at different depths.
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Heliox – Heliox is simply helium and pure oxygen; it is usually used by commercial divers to completely eliminate nitrogen narcosis. If you ever dive on Heliox, you’ll find that your body temperature drops; commercial divers use special equipment to combat hypothermia induced by this mixture.
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Heliair – A form of trimix blended from helium and air instead of helium and pure oxygen.
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Hydreliox – A blend of hydrogen, oxygen, and helium used for dives below 130 meters
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Hydrox – A mixture of oxygen and hydrogen used for deep dives. The US Navy has tested Hydrox at depths below 500 meters; the hydrogen content combats high pressure nervous syndrome. A diver named Theo Mavrostomos dove to 701 meters on Hydrox in 1990.
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Neox – Neon and oxygen; sometimes used in commercial diving, but with a reputation for the “neox bends,” a particularly severe form of DCS.
The Mixed Gas Advantage
Advanced wreck divers and technical divers put the ability to focus at the top of the list of advantages, particularly since deep wreck penetration requires intense caution and heightened awareness. Courses in mixed gas diving are often taught at depths upwards of 55 meters. For example, as part of the PADI Tec Trimix Diver Course, you will learn to plan and execute dives using mixed gas, use decompression software to create custom dive plans and dive tables, and finally, you will make training dives to as deep as 90 meters. Once you have completed the training, you will have access to sites very few divers have ever seen.
Mixed gases can help prevent narcosis induced wreck penetration; they help divers make sound decisions rather than errors in judgment. They help to eliminate overconfidence and confusion, allowing for a greater safety margin and better diving overall. While you will definitely pay a bit more for mixed gas, you’ll find that it is a worthwhile investment.