diving trimix

Diving Trimix

If you are new to Technical diving or looking at getting into it, there is a word that you would have heard getting thrown around quite a lot. Trimix, and if you have already started your technical diving career then you probably have some basic understanding of what it is. However some divers may be unsure of why we use it, and it’s advantages and disadvantages.

diving trimix

What is Trimix?

To put it basically Trimix is a breathing gas with 3 main gasses in it. These are Nitrogen, Oxygen (standard breathing air) and Helium. It comes in endless different blends, all of which have their own use in technical diving. The main reason divers use Trimix  is to extend their depth. Using air the deepest that you can go is around 60M (however most training agencies say 50m or 55m). This is because as you go deeper the partial pressure of Oxygen gets too high and it would be unsafe to go any deeper. So to go deeper we must get rid of some of the Oxygen from the breathing gas. This is where Helium comes into the mix. Once we start to add some Helium the percentage of the other gasses begin dropping. This means we can start to go down further.


The main advantage of Trimix is that it allows us to go to places where we cannot go using air. There there is also one other major advantage. As you are probably aware, when we start to go deeper than around 30m we begin to feel the effects of ‘Gas Narcosis’ kicking in. Helium however is non-narcotic so when we start to add the Helium we reduce those narcotic effects. This is great if you are doing anything that is more complicated than just swimming around a wreck. For example, penetration or complicated navigation. Some training agencies will start to use it for going deeper than 30m, so narcosis doesn’t even become an issue.


There are however some disadvantages to Trimix, the main one is the price. Helium is not a cheap gas, and this is why rebreathers are becoming more and more popular. You can use trimix in a rebreather, which recycles the Helium because your body doesn’t use it. This can save considerable amounts of money!

If you are interested in extending your bottom depth then we can teach PADI Trimix 65 and Full Trimix (which maximum depth is 90m) or TDI Advanced trimix (which maximum depth is 100m). It is great training even if depth isn’t your thing as you will learn to deal with many problems all at once (with the surface not being an option)

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