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If you are curious about Trimix diving, either you are a fan of technical diving, or you have heard the call of deep diving. If this is your case, or if you are just curious, you are in the right place. In today’s article, we will explain what Trimix is, how it helps technical divers go deeper, and what types of Trimix diving there are. Ready? Let’s get started!
What is Trimix?
As we commented in the article: “5 Reasons to become a PADI Enriched Air Diver”, there are different types of gas mixtures. Trimix is one of them. If the usual mixtures use oxygen and nitrogen, Trimix adds the third gas: helium.
Why add helium to the gas mixture?
1. Trimix diving helps to reduce nitrogen narcosis.
Below 30 meters / 100 feet in depth, divers are exposed to nitrogen narcosis, also known as deep-sea drunkenness. This phenomenon is linked to the increase in the partial pressure of nitrogen. In Trimix diving, your tank has a lower percentage of nitrogen than in the normal ones, so it reduces the possibility of narcosis.
2. Trimix diving helps to reduce exposure to high oxygen partial pressures.
Beyond 65 m/213 ft, oxygen reaches too high a partial pressure and becomes toxic to the central nervous system. To reach these depths, tech divers increase the quantity of helium in the mixture and reduce the percentage of oxygen. As a result, they have less risk of toxicity. Humans could not dive as deep as we do if Trimix diving did not exist.
3. Trimix diving allows you to breathe a less dense gas.
As we know, as far as pressure increases with depth, divers must make more effort to breathe. However, if we could have a less dense gas in our tank, we could breathe more easily. Helium works in this way, as it is a very light gas. Trimix diving makes scuba more comfortable.
Trimix Diving: Why We Do Not Always Dive in This Way?
The reason why we do not introduce helium into the usual gas mixes is simple. Helium is extremely expensive and rare. For example, in many places around the world, technical divers have to order helium well in advance of their diving trips. As a result, filling the tank becomes very expensive. A tank to dive to 60 meters/197 feet in depth can be more than 142 USD.
Types of Trimix diving
We can divide Trimix diving into two big groups, these are normoxic Trimix diving, and hypoxic Trimix diving.
1) Normoxic Trimix diving.
As we have already indicated above, oxygen begins to be toxic from 65 meters/ 213 feet. Above that depth, the concentration of oxygen in our tanks is between 18% and 21%. Remember usual tanks have 21% oxygen and 79% nitrogen. As in normoxic Trimix diving, the mixture adds helium, there is less nitrogen than in the normal ones. Therefore, divers are less likely to suffer from narcosis.
2) Hypoxic Trimix diving.
However, below 65 meters the percentage of oxygen that is compensated with helium must be reduced. Generally, oxygen levels do not fall below 12%
How Do You Know What Percentage of Oxygen and Helium Is in The Bottles?
As divers gain depth, they will change the bottles to adjust the percentage of oxygen and helium to their needs.
To know how to express the percentages in the cylinders we must say that in all the mixtures the percentage of oxygen is indicated, followed by that of helium and not that of nitrogen which, if necessary, is obtained by difference. Thus, in a cylinder with 15% oxygen, 55% helium and 30% nitrogen we would see this expression Tx 15/55.
It is vital to calculate the decompression stops and to consider the change of bottle to prepare the Trimix diving immersion meticulously.
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