What is Trimix Diving? – The Perfect Gas Mix for Scuba?
You hear Trimix and think about mixing ingredients and baking a cake? Chances are, you’re on the wrong website.
Otherwise, if you want to know more about Trimix diving then you’re actually in the right place! Just below the following image will be the boring stuff that describes what trimix is and what it means to go Trimix diving.
What is Trimix?
Trimix, simply put, is a blend of helium, oxygen, and nitrogen that allows divers to reach depths previously thought impossible. The exact percentage of the three will depend on the depth of the dive.
Let’s have a look at what you need to know about Trimix diving so you can judge for yourself whether it is the perfect gas blend when you learn technical diving!
Is there only one Trimix?
Trimix is a mix of gases consisting of oxygen, nitrogen, and helium in varying percentages. It is not a breathing gas that is made for recreational diving. Instead, it’s used by a Trimix diver to dive into deeper depths.
A Trimix diver can dive as deep as 300 feet (around 90 meters) or deeper. You do need to get a Trimix diving certification first and you should use gear, e.g. a dive computer, that is Trimix diving capable. Most gear for recreational diving can handle an Air Nitrox mixture but not necessarily Trimix.
If you plan to dive deeper, then the amount of oxygen and nitrogen needs be lowered and the helium increased to prevent nitrogen narcosis and reduce the risk of oxygen toxicity. The math behind the exact percentages is quite precise and complex. The use of Helium as part of your breathing gas allows you to set your own Equivalent Narcotic Depth (END) to optimize your gas to extend your depth range.
A typical Trimix gas blend for technical diving has around 44% nitrogen and 21% oxygen content. Then there’s Helium added at around 35% to make it a useful and safe Trimix diving gas mixture.
How do you know what percentages of which gas are in Trimix?
The Trimix naming convention consists of listing the percentages of oxygen and helium. Sometimes the nitrogen percentage is also added. If you see for example Trimix 21/35 then the mix has 21% oxygen, 35% helium, and 44% nitrogen.
Many, if not most, mixes are Normoxic Trimix. These are gasses that have around 21% oxygen (minimum is 18%) and varying levels of helium and nitrogen. Normoxic trimix blends are used for deep dives of up to around 200 feet (65 meters).
For deep dives beyond that, Hypoxic Trimix is used. These are blends where the oxygen content is less than 18%. For example “Trimix 10/50” would be 10% oxygen and 50% helium to let you dive deeper than 200 feet.
Why use Helium for Breathing?
Oxygen as well as nitrogen are pretty standard when it comes to breathing gas, so you may be asking yourself why helium was chosen as the third element. For one, helium has a lower density, which is easier to breathe at extreme depths.
With smaller bubbles than nitrogen, diffusion of helium in the tissues and blood is much faster and easier than other gases, lowering the risk for getting the Bends. Helium is also non-reactive with other chemicals and much less narcotic than nitrogen.
Indeed, many divers express that they feel better after finishing a dive with mixtures containing helium rather than solely nitrogen and oxygen, though the claims haven’t been empirically tested.
Unlike some other breathing gas mixes, Trimix is reserved largely for professional or technical divers. Recreational divers generally wouldn’t reach the depths necessary for these special measures. We’ll talk a bit later on why this mixture is reserved for specialized use.
What’s the history of Diving with Trimix?
Trimix is one of the advances in the world of scuba diving that we can attribute to the military. At the end of World War II, the US military and British navy began to experiment with diving technology.
They wanted to see if they could reach new depths. One of the experiments that they conducted was around the use of Helium in saturation diving to reach sunken military equipment.
For a few decades, the results of these studies didn’t branch out of military circles, but by the 70s and 80s, helium mixtures were being used by technical divers for cave diving. A decade later, practices were being standardized in terms of training, making trimix more widely accessible than it was just thirty years before and commonly used for technical diving.
Today, Trimix is used for pretty much any dive that exceeds 150 ft. A Trimix diver uses it to reach those depths safely and with a lower risk of inert gas narcosis or oxygen toxicity.
Are there Drawbacks when you Consider to Dive with Trimix?
Since helium seems to be a cure-all for issues of toxicity and narcosis, it’s interesting that not all tanks are filled with the stuff. But there are a few good reasons why it’s not more commonly used and you don’t have everyone be a trimix diver.
For one thing, helium comes with additional expenses. This is largely due to the fact that it’s not that easy to get and it requires special training. Decompression with trimix is slightly more complicated than traditional mixtures, so divers must be trained on how to avoid decompression sickness.
Take care in ensuring that you will not exceed your decompression limit during Trimix decompression dives!
Another disadvantage to helium is that it lowers body temperature and puts divers at higher risk for a condition called High-Pressure Nervous System or HPNS when they are Trimix diving.
Once called helium tremors, this condition can sometimes occur for dives exceeding 600 fsw (foot sea water) and manifests in fatigue, nausea, shaking, and cognitive disruptions. While very uncommon, researchers still worry about this risk of breathing helium.
Even with these drawbacks, mixes that utilize helium are overall very safe for Trimix diving and even preferable to more standard breathing gases.
How can you learn more about Trimix Scuba Diving?
Trimix isn’t something that you would simply put in your tank and dive as you do normally. There are a lot of factors that go into finding the right mixture, and you should be prepared to take a few classes to take Trimix diver training and get certified to go Trimix diving. Check with your local dive community to learn more about prerequisites and opportunities to join a class on Trimix diving.
For PADI certification in Trimix diving, for instance, you need to have a PADI Tec 65 Diver certification for technical diving as well as 100 logged dives. You must also be over 18 years old and have medical clearance so you get certified as a Trimix diver.
In a class like this, you’ll learn key skills like planning trimix mixtures for different depths, handling multiple decompression cylinders, use of decompression software, and multi-gas computers.
You’ll also, of course, learn how to deal with emergency situations, which is extremely important the deeper you plan to dive. Remember that diving into such depths requires a lot more dive planning upfront to make sure that all scuba divers are safe!
An initial class on trimix with PADI would allow you to dive to a maximum depth of 210 feet (or 65 meters) or less, meaning that there is still more to learn on the topic of trimix before you can think about diving even deeper.
Take your Diving Further and Deeper
For those who are contemplating becoming certified in trimix, it’s a good idea to do extensive research on the ins and outs of how to use the breathing gas. With a solid theoretical base, you’ll be sure to enjoy your certification classes and be safer in the real-world environment as a Trimix diver!
If you want to save money on gas costs yet do want to do a lot of deep diving, consider using a rebreather instead of diving with Trimix as your decompression gas! Dive shops will change a fee to fill your diving cylinder and if you switch to deep diving with a rebreather you can save that fee every time you go diving!
