What’s the most important thing you take underwater with you? If you’re like most divers, you’ll agree that it is your breathing gas. There are many different types of gas; various blends have been developed as diving evolved, and researchers are still working to come up with the perfect breathing blend, since standard air is not suitable for deep, high-pressure environments. Here, we’ll take a closer look at various gases and breathing blends.
Air
Standard breathing air contains 78% nitrogen, 21% oxygen, and 1% other gases. It is the least expensive to procure, as it’s simply compressed atmospheric air with nothing added. Since nitrogen causes narcosis and as the risk of narcosis increases with depth, standard air is typically safe to a maximum depth of just 130 feet or 40 meters. As most beginners and recreational divers stay well within this limit, air is the gas of choice for most.
Nitrox
Nitrox is any air mixture that contains more than 21% oxygen, with content usually somewhere between 32 and 36%.
The main benefit of diving with nitrox is that it helps to prevent the potential for nitrogen narcosis. This problem occurs as nitrogen is absorbed by the body. It generally leads to feelings of wooziness similar to those which come with intoxication, and it can also lead to magnified emotions and perceptions. Some people begin to think everything is funny, and others, particularly those who tend to be anxious, can suffer full-blown panic attacks because of narcosis.
While nitrox is suitable for diving to depths beyond 40 meters, it is also great for diving at shallower depths as it can allow for more bottom time and as it can reduce the need for safety stops. Nitrox is the most basic of all the enriched gases available, and it is normally used by advanced recreational divers as well as some technical divers. In order to use nitrox, you’ll need to take a nitrox diving course. In the event you hope to progress to other mixed or enriched gases, nitrox is the first one you’ll need to learn to use.
Trimix
Trimix is usually used by technical and commercial divers, as it allows for extended bottom time and permits divers to reach greater depths without fear of nitrogen narcosis or oxygen toxicity. This blend is a combination of oxygen, nitrogen, and helium. Its helium content replaces part of the oxygen and nitrogen air and nitrox contain, and it allows for diving to a depth of 100 meters. The standard trimix blend contains 19% oxygen and 30% helium. The remainder of the blend is usually nitrogen.
Heliox
This mixture contains only oxygen and helium; it is only used once a diver reaches depth, with traveling gas being used until that point. Heliox allows for dives to as deep as 300 meters; as the blend contains no oxygen, the chance of nitrogen narcosis is completely eliminated, as are many problems associated with decompression.
Hydrox
This breathing gas is highly volatile, which is the main reason it is used less frequently than other blends. It contains hydrogen and oxygen, both of which are highly explosive on their own, and which are equally explosive when blended. This is unfortunate, since this blend is easy on the body, allowing for diving to deep depths and eliminating much of the potential for decompression sickness as well as other negative side effects.
Hydreliox
Typically used for commercial diving and for scientific diving, Hydreliox contains helium, oxygen, and a small amount of hydrogen. As it contains no nitrogen, the risk of nitrogen narcosis is eliminated; however, hydrogen shows some signs of promoting narcosis at depths greater than 300 meters. Even so, this innovative breathing gas has been tested at depths of up to 500 meters, and is considered to be extremely safe and effective for diving to depths of up to 130 meters; beyond this, the blend carries a risk of high pressure nervous system.
Pure Oxygen
Pure oxygen is not used as a breathing gas for diving; it is typically only used to supplement other blends during short decompression stops. It can also be used after a deep dive; for example, commercial, military, and scientific divers sometimes breathe pure oxygen after deep dives as a method for helping to prevent decompression sickness. While you might think oxygen is safe to breathe on its own, the opposite is true; breathing too much pure oxygen can lead to toxicity.
No matter what breathing gas you are using, it’s vital to test your cylinders for contaminants. If you are filling your own tanks, be sure to do so away from running engines and other things that can contaminate outside air. Just as some gases can be beneficial, others can cause harm and lead to death when present in excessive amounts.
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Carbon dioxide – This gas is produced by the metabolic process and is released from the body during respiration. When breathed in excess, it can lead to carbon dioxide poisoning.
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Carbon monoxide – Carbon monoxide is a product of incomplete combustion. When breathed in excess it can adversely affect health, and it can lead to neurological damage, hypoxia, and even death.
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Hydrocarbons – Hydrocarbons are present in fuels and in compressor lubricants, and they can also be released during incomplete combustion. These compounds can make their way into dive cylinders when air is contaminated, and besides being harmful to breathe, they can fuel combustion. When any mix containing 21% oxygen or more is contaminated with hydrocarbons, it carries an even greater risk of explosion.
The search for the perfect breathing gas isn’t over; in fact, technical advancements are bringing us closer than ever to the discovery of a gas that will allow us to go even deeper while preventing health problems associated with the gas blends we have available today. So if you’re among those who want to head into the deepest, most mysterious reaches of the underwater world, don’t lose hope. Perhaps that perfect breathing gas will be discovered someday soon.