Helitrox: What’s in a Name?

Label on helium tank for helitrox

Scuba has more than its share of acronyms, banter, and confusing jargon, but Helitrox may take the cake. So what is it and why do you need it?

I call helitrox “Trimix Lite.” Like trimix, helitrox is a mix of oxygen, nitrogen, and helium. The difference is, helitrox may only contain up to 20% helium and no less then 21% oxygen. So it’s like taking the air we’re all used to breathing and replacing some of the nitrogen with helium. But why?

Why Helitrox?

Here’s the deal with helium, it’s much less narcotic at depth than nitrogen. Take a moment and let that soak into the gray matter. Helium is virtually non-narcotic at depth. As divers, we’re always concerned with narcosis. We know that under pressure, nitrogen affects our mental processes. It becomes difficult to concentrate, you may experience perceptual narrowing (like tunnel vision), you may even forget to keep track of depth, bottom time or how much gas you have left. Obviously these are potentially life-threatening circumstances. Narcosis is a concern for all divers, more so for technical divers who venture beyond recreational limits. Narcosis is an even bigger threat for Great Lakes divers, where cold water and limited visibility may exacerbate the effects of nitrogen narcosis.

So if we want to manage narcosis, we need to manage nitrogen. We need to replace some of the nitrogen in our breathing gas with something that isn’t as narcotic. Voila, helium! By adding 20% helium to our gas, we get a mix called helitrox. As noted earlier, helitrox is a limited version of trimix. I’ll spare you the math, but the bottom line is that when you breathe helitrox at 150′, you experience a similar narcotic effect as breathing air at 100′. In the Great Lakes, that’s a huge advantage.

No More Adv. Nitrox/Deco Procedures

The TDI Helitrox Diver course is identical to the Decompression Procedures course with the addition of some academic work to cover breathing helium-based mixes and a couple extra dives. I’m offering the Helitrox Diver certification to all my incoming Adv. Nitrox/Deco students. With a combination program consisting of Adv. Nitrox, Deco Procedures and Helitrox Diver, my students will be able to:

  • plan and execute dives requiring staged decompression to a maximum depth of 150′ (Deco Procedures)
  • use Helitrox as the bottom gas to mitigate the effects of nitrogen narcosis and maintain an Equivalent Narcotic Depth of 100′, and
  • use oxygen-rich mixes (including pure oxygen) as decompression gasses to optimize decompression strategy (Adv. Nitrox)

When contemplating making the jump to technical diving, ask potential instructors if their entry-level technical diving course includes the use of helium. If it doesn’t, ask them why not. If you think managing narcosis is important and want to learn about using helium right from the beginning of your tech diving career, contact me for your course. It you are already certified as an Adv. Nitrox/Deco Procedures Diver, we can do a stand alone Helitrox Diver course or it may make more sense just to go straight into Trimix Diver. Again, get in touch with me to discuss options.