Scuba diving can be an amazing experience. If you are like most people, the moment you made your first dove, you were hooked. That’s how we felt at least. We wanted to dive everyday once we finally had our open water certification.
But, like many things, normal diving eventually becomes repetitive after a hundred dives. So, we began branching out. We got into wreck diving and became interested in underwater photography. But, there was a definitive next step we had to take in order to really move on to the next level. We needed to be able to dive for longer and down to more challenging depths.
Luckily, there is a way to do this. It’s called mixed gas diving. If you’re ready to take the plunge and increase your scuba skills, we’ll go over everything you need to know.
First, we’ll discuss what mixed gas diving is. Next, we’ll take a look at some of the safety considerations that you should be aware of. Then, we’ll take a look at the equipment you need for mixed gas diving. Finally, we’ll examine the top five dive sites around the world requiring you to use mixed gasses.
What Is Mixed Gas Diving?
Normally, when you go scuba diving, the air you breathe is the regular air that you breathe every day. This is usually composed of around 78% nitrogen, 21% oxygen, and 1% other gases. This air has been run through a special compressor made especially for diving. The compressor purifies the air and dehumidifies it to make it safe for breathing.
The air you normally use when recreational scuba diving allows you to go up to 40m (130ft). Any deeper and you risk a host of complications that can potentially lead to serious injury or death. These complications include:
- Decompression Sickness
- Nitrogen Narcosis
- Running out of Air
There are certainly people who do exceed this 40m (130ft) limit. But, most diving organizations have set this as the standard for regular air diving. As a new diver, you should make sure you are sticking to all of the regulations for depth limits. As a new open water diver, this means you should not go past 18m (60ft). For advanced divers, you are recommended to not go past 30m (100ft). Going past these limits puts you at a significant risk of something going wrong during your dive. Especially, if you are only using air.
What if you want to go deeper though?
This is where mixed gasses come in. Mixed gasses are often used when you start to get into technical diving . The exception is recreational Nitrox diving which is usually not considered technical diving . Mixed gasses have different gasses such as Oxygen, Nitrogen, and Helium. Different mixtures are created for different dive profiles. The purpose is to decrease the risks that deep-diving presents.
Usually, the first mixed gas that you will use is Nitrox. You will need to take a course on using Nitrox in order to become certified in this type of diving. Nitrox allows you to dive with a reduced risk of decompression sickness. It can allow you to dive for longer periods at a similar pressure level. For this reason, it is used much of the time for activities like cave diving and wreck diving. But this is only one of the different types of mixed gas that are commonly used by advanced divers and technical divers.
Let’s take a deeper look at the different gas mixtures in more depth:
Nitrox Diving
As we stated before, this is the most common type of mixed gas used by divers. Especially for recreational divers and those new to mixed gas diving. Nitrox is often the first mixed gas many divers will use and become certified with.
It is a mixed gas composed of oxygen and nitrogen with higher concentrations of oxygen than normal air. This helps slow the absorption of nitrogen into the bodies tissues. It also decreases decompression requirements as well as the risk of decompression sickness. This in turn increases underwater dive times.
There are two primary mixtures for Nitrox for recreational diving. The first is a mixture with 32% oxygen and the second is 36% oxygen. Technical divers will often use oxygen mixtures much higher than this.
Trimix Diving
This is a mix of Oxygen, Helium, and Nitrogen. Trimix is not used for normal recreational diving so as a new diver you are not likely to come across it. Instead, this is used for technical diving and advanced recreational dives. It is primarily for deep dives during the deeper phases. In many cases, Nitrox is used during the descent and Trimix is used during the deeper parts.
The Helium is added in order to help decrease the risk of both nitrogen narcosis as well as oxygen toxicity. The downside of Helium is that it is very expensive. For closed circuit rebreather divers, who are recycling their air mixes, this is less of an issue. However, for open circuit divers, this can make Trimix and Heliox (helium and oxygen) much more expensive. There are also fewer Trimix filling stations which makes obtaining tanks logistically more of a challenge.
Helium mixtures have been in use since the early 1900’s. There are a few standard mixtures which makes filling tanks easier. But, gas mixtures are often optimized based on the depth of each dive.
Heliox Diving
This is a mixture of oxygen and helium without nitrogen. Heliox is more often used in commercial saturation dives due to the expense of helium. It is primarily used for deep sea diving to help lessen the chances of decompression sickness.
As with Trimix diver, scuba filling stations that handle helium are less common than normal air filling stations. This adds significantly to the cost of each tank and makes obtaining tanks and fills logistically more challenging.
Heliox tanks can run hundreds of dollars for single fills. A typical Heliox mixture is usually around 10% oxygen. The low level of oxygen helps to prevent oxygen poisoning.
Hydreliox Diving
This is another breathing gas mixture used during deep sea diving. It is used similar to Trimix to prevent complications from deep sea diving such as high-pressure nervous syndrome. HPNS can be an issue for divers using Heliox past 130m (430ft). To combat this, either hydrogen or nitrogen is added to the mixture. When nitrogen is added, it becomes Trimix. When Hydrogen is added, it becomes Hydreliox.
The typical mixture for Hydreliox is less than 5% oxygen. This helps to lessen the chance of exploding due to the volatility of Hydrogen. Hydreliox is used during deep technical dives and commercial dives. The risk of Hydrogen narcosis is present when using Hydreliox. This, combined with the risk of explosion, limits the use of hydrogen in diving.
Other Gasses
There are other gas mixes such as Argox, Argon and Hydrogen, and Hydrox, Hydrogen and oxygen. These gas mixes are used very rarely or, in the case of Argox, only theoretical mixtures. The above dive gas mixtures, Nitrox, Trimix, Heliox, and occasionally Hydreliox, are the most common. Unless you get into technical or commercial diving you will only use Nitrox.
Mixed Gas Diving Safety
Mixed gas diving is a high level activity. To even get started doing these types of dives, you will have to take specialized classes. As we mentioned already, you are typically going to start out with Nitrox as the first gas mix you work with. You will be required to take a special class for learning to work with Nitrox specifically.
After you get some experience under your belt you can then move on to technical diving classes. It is imperative that you pay full attention in these classes. Mixed gas diving can be incredibly dangerous when done by inexperienced divers.
The Divers Action Network estimates that around 20 people die each year while mixed gas technical diving . This number is quite high due to the smaller number of technical divers in total. If you factor in non-technical mixed gas dives, such as regular recreational Nitrox dives, this number is likely much higher.
The main thing to remember about diving deaths, especially mixed gas diving deaths, is that they are usually preventable. Most diving fatalities happen due to inexperience or failure to follow safety protocols. This goes for both newer divers all the way up to dive instructors with hundreds of regular and mixed gas dives in their log book.
Some of the main dangers of mixed gas dives include:
- Decompression sickness
- High-pressure nervous syndrome
- Oxygen narcosis
- Nitrogen narcosis
- Hydrogen narcosis
- Oxygen toxicity
The main thing we want to stress to you is that these hazards can be minimized with careful planning. One of the leading causes of diving fatalities, outside of inexperience, is complacency. Especially when it comes to mixed gas diving and technical diving, this can be an issue. By the time you get to these types of diving you will likely have logged dozens to hundreds of dives. After doing so many dives, it is easy to feel too comfortable. You can read many stories of high level divers whose death could have been prevented with a simple pre-dive safety check. They got complacent so don’t let yourself fall into this trap.
Also read: Muck diving tips
If these things can happen to divers with as much experience as a dive instructor, then don’t think it can’t happen to you. Always follow proper safety protocol. Always make sure you know your equipment inside and out and keep everything properly maintained. Make sure you are regularly servicing your dive computer, especially when mixed gas diving. Last, always make sure you are doing pre-dive safety checks for your equipment and checking your air for any issues. These simple and easy to do things will keep you safe. Even when doing complex mixed gas dives.
Mixed Gas Diving Gears
In general, the equipment used when mixed gas diving and technical diving is mostly the same as regular recreational dives. You still use fins, wet or drysuits, a mask, etc. There are some differences that are important to take into consideration. Let’s do a quick toe to head breakdown of equipment to see what you will need:
Mixed Gas Diving Fins
If you are doing regular recreational dives with nitrox, you can pretty much use whatever you are comfortable with. The weight of the tank and setup is going to be similar to what you are used to with regular air.
But, if you are getting into technical diving, you will want something a little different. Dive fins for technical diving tend to be stiffer and more flared out. The tank setup and rig for technical diving is a bit heavier so you want fins that give you good thrust. The general rule is that you want to avoid split fins. Also, if you are heavier toward your head, which most people are, you want heavier fins to help balance you out. If you are foot heavy, you want lighter fins for the same reason.
Try these:
Mixed Gas Diving Wetsuit / Drysuit
When mixed gas diving, the decision to use a wetsuit or drysuit comes down to depth, water temperature, and duration. Even in warm water, deep diving is going to take you to some cold places.
You probably want to have at the very least a 5mm wetsuit for deeper dives. For recreational Nitrox dives, you will be fine with the normal thickness you would wear with regular air. If you’re prone to getting cold, a 1mm wetsuit under your normal suit should do the trick.
If you are doing deep technical dives or cold water dives, then a drysuit is the way to go. Keep in mind that drysuits are a whole different animal. You can’t just hop in and go. They require specialized knowledge to use correctly. Before you get into diving with a drysuit, regardless of whether it is a mixed gas dive, we recommend you take a drysuit specialty course .
Mixed Gas Diving Dive Computer
For mixed gas diving, you need a specialized dive computer which can handle all of the different gasses and tanks you will be using. It is not uncommon during a mixed gas dive, especially deeper technical dives, to have three or more tanks each with various mixes. Your average dive computer simply can’t handle this.
You want a computer that can measure at the very least regular air, Nitrox, and Trimix. It is very rare that you will use Hydreliox during a mixed gas technical dive and you will not be using it for recreational dives. Instead, Hydrogen is primarily used during saturation diving. So, you will not need to worry about Hydrogen when getting a mixed gas computer.
If you are new to mixed gas diving, you want a computer which has a conservative algorithm. This will help you stay safe by limiting bottom time and overestimating decompression times. As you begin to improve your diving skills with mixed gasses you will be able to more liberally calculate these.
Mixed Gas Diving BCD
If you are doing recreational dives with Nitrox, you will be fine with your normal jacket style BCD. But, if you plan on doing technical dives then you need a wing type BCD. This is a BCD where you have a harness with either an aluminum or steel backplate. The air bladder connects to the backplate.
You can use either a twin mount or a sidemount during your dive. Twin mounts are when a diver uses two tanks strapped to their backs. They can also be used with side mounts for cave or wreck diving. This is where your tanks are mounted to your sides allowing you to easily unclip them in the event you need to fit through a tight space.
Mixed Gas Diving Mask
Any quality dive mask rated to the appropriate depth will work. Some mixed gas divers prefer to use a full-face gas mask. But, this is not a requirement for mixed gas diving or technical diving.
Other Mixed GAs Diving Equipment
There is other equipment that you need for mixed gas diving. As you go through the different mixed gas classes, you will learn the specific equipment you will need for each type of dive.
Top Locations For Mixed Gas Diving
Now that you know what mixed gas diving is and what you will need, let’s look at where the best places for mixed gas diving are.
1. Cocos Island, Costa Rica
This is one of the most famous locations for diving around the world. Jacques Cousteau is attributed as saying that the best diving in the world can be found at Cocos Island. One of the main reasons people dive here is the massive amount of sharks. Especially Scalloped Hammerheads, which congregate around the island. This island is only accessible via liveaboard due to its remote location in the Pacific Ocean. You will be doing a large number of dives. Usually over a 6 – 8 day period. This, combined with the depth of many of the dives, means that Nitrox is a must to really get the most out of your trip.
Best time to dive: June to December
2. Darwin Island, Galapagos Islands
The Galapagos Islands are famous for the exotic and unspoiled wildlife on the islands. There are species, such as the marine iguana, which can only be found in the Galapagos. It shouldn’t be a surprise that under the ocean is equally as robust.
While all of the islands can be good for diving, the most famous spot is Darwin Island. Especially, because of Darwin Arch, known for giant groups of hammerheads, whale sharks, and other pelagic species.
It is possible to do many of these dives with regular air. But, if you want a truly great experience, you need to book a liveaboard and do multiple dives each day. In which case, Nitrox is the way to go.
3. Raja Ampat, Indonesia
Divers around the world regard Raja Ampat as the holy grail of diving destinations. This is due to the untouched reefs, robust marine life, and crystal clear waters. There are many islands which each have numerous dive sites you won’t want to miss.
You can see everything here including large schools of barracuda and tons of pelagic species. Because of the large number of dives you will be doing it is highly recommended that you use Nitrox on these dives.
Best time to dive: October to April
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4. The Pit, Tulum, Mexico
Mexico is famous among divers for Cenotes. These are flooded sinkholes which often have crystal clear water running through them. One of the more popular Cenotes is The Pit.
This is a famous location for technical divers due to its extreme depths. You need to be both cave diving as well as Trimix and Nitrox certified to make this dive. The Pit is located near the town of Tulum near the northeast corner of the Yucatan Peninsula.
Best time to dive: May to September
5. Blue Hole, Dahab, Egypt
This is one of the most famous and infamous diving spots in the world. It is entirely possible to dive in the Blue Hole with regular air if you only want to stay towards the top and see the hole.
But, if you want to really explore the cave and, more importantly, swim through the arch, you have to use mixed gas. The reason this site is infamous is because many people have died here who did not have the right experience and were not using mixed gas. They try to swim through the arch and ran out of air. The depth profile of the arch mandates that you use Trimix if you want to safely make the dive.
Best time to dive: July to September
In Conclusion
Mixed gas diving isn’t for everyone. You can probably figure that out from all of the hazards associated with it. But, if you are at the limits of recreational diving with regular air, it could be fore you.
Do you think you’ll be getting into mixed gas diving?
Have you just completed a Nitrox or Trimix course and have some advice?
Let us know in the comments what you think. We love hearing from divers like you what your experiences have been. You also never know how your information can help a fellow diver.
