diving logbook - 3
The Diving Logbook, Why Is It So Important?
April 6, 2021
Adventure dives (1)
Top 5 Adventure Dives to Get Your PADI Advanced Open Water Certification
April 15, 2021
Show all

5 Types of Mixed Gas Diving or Gas Blending

mixed gas diving - 2

If you are a follower of this blog, you already know that there are different mixed gas diving possibilities. In this article we are going to review them, to delve into their properties and we will also see new mixtures we had not yet told you about.

Recreational Mixed Gas Diving

  1. Compressed air. This is the most common mixture, the mixed gas diving percentage is 21% oxygen, 78% nitrogen, and 1% other trace gases. The use of this gas blending does not require training beyond that obtained in the Open Water course. This is not the case with all other mixed gas diving.
    This gas blending is only usable up to 40 meters / 130 feet, which are the limits of recreational diving. If you want to delve into this topic, we recommend the article Open Water Depth Limits: Everything You Should Know. The main problem is the nitrogen contained in this mixed gas diving. Beyond 40 meters / 130 feet depth, there is a danger of nitrogen narcosis. Also, as we know, nitrogen dissolves in the body and you need a slower ascent rate and decompression stops to safely remove it. This is the reason why other mixes are used.
mixed gas diving - 4

2. Nitrox or enriched air EAN. This mixed gas diving allows you to increase underwater time, but it does not allow you to dive deeper. Why? As we already told you in the article. 5 Reasons to become a PADI Enriched Air Diver there are different Nitrox gas blendings.

  • EAN32 or Nitrox I: 32% oxygen and 68% nitrogen. This is the mixed gas diving that you can find in Dressel Divers and enjoy for free.
  • EAN36 or Nitrox II: 36% oxygen and 64% nitrogen.
  • EAN40: 40% oxygen and 60% nitrogen.

As you can see, the percentage of oxygen is higher in any Nitrox gas blending than in the compressed air. This poses a risk due to the toxicity of oxygen at high pressures. The more oxygen the mix has, the less depth you can go. This is why Nitrox divers must be trained as they need to learn how to calculate what their exposure to oxygen is going to be, based on the pressure and duration of the dive.

Technical Mixed Gas Diving

3. Trimix: We already told you about this mixed gas diving in the article: ” Trimix Diving or How to Go Deeper ” In Trimix, oxygen, nitrogen and helium are mixed in different percentages depending on the diver’s needs. By substituting part of the oxygen for helium, we reduce the risk of oxygen toxicity or nitrogen narcosis. Therefore, this mixture of diving gases allows us to descend deeper. Of course, anyone who intends to dive with Trimix needs additional training.

The basic problem with Trimix is ​​that Helium is very expensive and its price rises more and more.

4. HeliAir. Actually, this is the name given to a kind of Trimix mixed gas diving, since it mixes the three gases; oxygen, nitrogen, and helium. But It receives a special name for the way in which it mixes them. While in the Trimix oxygen and helium are first mixed and then completed with compressed air, in HeliAir, helium is added first and then compressed air, which results in a physiologically poor mix. HeliAir is hardly used anymore, except at remote sites that don’t have the equipment to make custom Trimix mixes.

5. Heliox. Heliox, however, is not Trimix, because this mixed gas diving does not contain nitrogen, only helium, and oxygen. Heliox mixed gas diving is used mainly in the professional world, which is performed at great depths, generally with rebreathers. When doing this mixed gas diving, the oxygen ratios vary depending on the depth, but usually never exceed 21% of the total mix. This gas blending is extremely expensive, however, for deep dives with a rebreather, it is quite convenient, because it does not present any risk of nitrogen narcosis. In contrast, it is a rapidly diffusing diving gas mixture and it requires longer decompression stops.

Do you want us to answer a question about mixed gas diving? Contact us!

mixed gas diving - main
mixed gas diving - main

4. HeliAir. Actually, this is the name given to a kind of Trimix mixed gas diving, since it mixes the three gases; oxygen, nitrogen, and helium. But It receives a special name for the way in which it mixes them. While in the Trimix oxygen and helium are first mixed and then completed with compressed air, in HeliAir, helium is added first and then compressed air, which results in a physiologically poor mix. HeliAir is hardly used anymore, except at remote sites that don’t have the equipment to make custom Trimix mixes.

5. Heliox. Heliox, however, is not Trimix, because this mixed gas diving does not contain nitrogen, only helium, and oxygen. Heliox mixed gas diving is used mainly in the professional world, which is performed at great depths, generally with rebreathers. When doing this mixed gas diving, the oxygen ratios vary depending on the depth, but usually never exceed 21% of the total mix. This gas blending is extremely expensive, however, for deep dives with a rebreather, it is quite convenient, because it does not present any risk of nitrogen narcosis. In contrast, it is a rapidly diffusing diving gas mixture and it requires longer decompression stops.

Do you want us to answer a question about mixed gas diving? Contact us!

Leave a Reply

Your email address will not be published. Required fields are marked *