What is Trimix? What is Helitrox?

While Nitrox refers to any breathing gas mixture where nitrogen and oxygen are the primary components, Trimix is a blend of three gasses. Most of the time trimix refers to a gas mix containing oxygen, nitrogen, and helium. Trimix 16/40 refers to a gas that is 16% oxygen and 40% helium. The fraction of nitrogen is not expressed. Helitrox is a specific blend of trimix: 26/17 (26% oxygen, 17% helium).

What do I Learn in the NAUI Recreational Helitrox Class?

In this class we discuss:

• A review of basic Nitrox concepts.
• Equipment configuration.
• Advantages of alternative breathing gasses.
• Helium gas properties.
• The physiology of deep diving.
• Decompression models and RGBM.
• Helitrox diving protocols and safeguards for use.
• Gas management for deep dives.
• Individual and team dive planning and execution.

There is significant work on in-water skills as well.

What are the Benefits of Diving With Helitrox?

The primary benefit of using Helitrox on deep dives is a reduction in the narcotic properties of the breathing gas. Nitrogen, at high partial pressures of three atmospheres or greater, has an anesthetic effect. You feel dopey, drunk, with impaired thought processes and reflexes. Most divers encounter this effect at about 100 feet when diving on air.

For recreational diving helium is added to the breathing gas to dilute the nitrogen and lessen the effects of narcosis. Consider an air dive to 110 feet:

• The partial pressure of nitrogen in the gas is 3.4 atmospheres; well above our limit of three atmospheres.
• For a Helitrox 26/17 mix the partial pressure of nitrogen in the gas is 2.4 atmospheres; well below the limit of three atmospheres.
• The result: During a dive to 110 feet on a 26/17 mix your head is clear, your reflexes are sharp, and you will feel better than the other air divers after surfacing.

Helitrox 26/17 should be the breathing gas of choice for any recreational diver diving deep.

Why do I Feel Better After a Dive on Helitrox?

Helium is a light, colorless, odorless, tasteless inter gas with low narcotic potency and low density. It is easy to breathe and it's diffusion speed is 2.7 times faster than nitrogen. It is one third as soluble and helium bubbles are smaller than nitrogen bubbles. Upon surfacing your body is "cleaner" than it would be if you were diving a high nitrogen mix.

Why is Additional Training Required to Dive With Helitrox?

A thorough understanding of the advantages and disadvantages of a breathing gas is absolutely necessary before using it in the water. Exceeding the operational limits of a gas can cause problems with either nitrogen narcosis or oxygen toxicity.

Helium has it's disadvantages. Helium does cost more than oxygen and nitrogen. Not a lot more -- but more.

Diving skills need to be better than those of your average diver. Precision buoyancy control is very important as well as the ability to control your ascent rate, ascend slow, and stop when required.

What is Oxygen Toxicity?

Oxygen toxicity is exactly what it suggests; oxygen poisoning the human body. There are two types of oxygen toxicity; central nervous system (CNS) toxicity and pulmonary toxicity. CNS toxicity is caused by short term exposure to high oxygen partial pressures and can result in convulsions. Pulmonary toxicity is caused by long term exposures to moderate oxygen partial pressures and leads to pulmonary problems. These two topics are discussed in detail in the Helitrox class.

What is Nitrogen Narcosis?

Nitrogen, at high partial pressures of three atmospheres or greater, has an anesthetic effect. Nitrogen narcosis is a state of stupor; or impaired thought and reflexes. In an emergency an impaired diver may make the wrong choices which can lead to disaster. Narcosis is sneaky because of its euphoric feeling. It increases gradually as you dive deeper.

Do I Have to Buy New Equipment to Use Helitrox?

No. The sole exception would be if your local dive shop mixes Helitrox by partial pressure blending. In that case, your tanks and valves need to be cleaned because pure oxygen is used in the blending process.