Sunday, May 8, 2011

Deep Sea Diving: What Is Trimix?

By Owen Jones


One of the most important aspects of scuba diving that a diver has to learn is how to set up the breathing tank. Divers do not utilize oxygen in their tanks, they use (or, increasingly, used to use) compressed air. However air is roughly 70 percent nitrogen and 30 percent oxygen and the nitrogen can cause nitrogen sickness under pressure, so more and more people are turning to Nitrox.

Nitrox is not air, but it is still made up solely of nitrogen and oxygen, although not in the same percentages, which you can vary. The problem with increasing the amount of oxygen in the mix is that there is a greater chance of suffering from oxygen toxicity the deeper you go. Therefore, the trade off is that the more oxygen you use, the shallower you may swim.

It sounds like a rough decision, you can suffer from either nitrogen or oxygen toxicity, take your pick. However, there is a third option and it is known as Trimix. Trimix is the 'air' that deep sea divers make use of. It is a mixture of three gases, as its name implies: nitrogen oxygen and helium.

Helium is used as a kind of filler. It does not do us any harm and it does not do us any good either, but it permits divers to take a lung full and it reduces the volume of nitrogen and the volume of oxygen thus decreasing the likelihood of sickness.

The only problem with helium is that it conducts heat five times more than oxygen and nitrogen. This leads some deep sea divers to suffer from a condition known as hyperbaric arthralgia. Hyperbaric arthralgia is a kind of joint pain that a number of divers experience as they go deeper than 100 feet in salt water.

Deep sea divers have to learn about the different Trimixes as part of their curriculum, because one day they will be accountable for choosing the mix they use. The option is not just compressed air, nitrox and Trimix, because there are different ratios of the gases in Trimix to take into the equation as well.

For example, a 10/70 Trimix will be made up of 10 percent oxygen, 70 percent helium (and 20 percent nitrogen). This kind of mix is appropriate for diving to a depth of 330 feet in salt water or 100 msw (metres in salt water). Fresh water is a little lighter than salt water. This does not matter at lower depths, but it does after a hundred feet.

Breathing and gases are merely one aspect of diving that you will have to learn if you would like to go diving. A different aspect of diving that is linked with diving is the rate of ascent. Divers used to get taught not to come up faster than their smallest bubbles, which is around 60 feet per minute. However, many instructors now think that this is still too fast and recommend 30 feet per minute with a three minute wait at 15 feet.




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