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. The deeper the dive plan, for instance, the amount of oxygen and nitrogen will be lowered and the helium increased to prevent nitrogen narcosis and oxygen toxicity. The math behind the exact percentages is quite precise and complex.
Oxygen and 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 finished 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 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, 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.
Today, trimix is used for pretty much any dive that exceeds 150 ft.
Are there drawbacks?
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.
For one thing, helium comes with additional expense. 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.
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. Once called helium tremors, this condition can sometimes occur for dives exceeding 600 fsw 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 and even preferable to more standard breathing gases.
How can you learn more?
Trimix isn’t something that you would simply put in your tank and dive as normal. There are a lot of factors that go into finding the right mixture, and you should be prepared to take a few classes to get certified in using trimix. Check with your local dive community to learn more about prerequisites and opportunities to join a class.
For PADI certification in Trimix, for instance, you need to have a PADI Tec 65 Diver certification as well as 100 logged dives. You must also be over 18 years old and have medical clearance.
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. An initial class on trimix with PADI would allow you dive to depths 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.
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!