Can You Scuba Dive With Pure Oxygen?

Last Updated: September 18, 2023

Scuba diving is a popular recreational activity with a lot of health benefits for the mind and body alike. With the world moving more and more towards environmental sustainability and the concept of using pure materials in products, one might assume the same for scuba diving with regards to the use of gases in the tank.

So, can you scuba dive with pure oxygen in the tank? Short answer: no, not under normal circumstances, as the human body is not designed to handle 100% oxygen for extended periods of time and might undergo health hazards such as oxygen toxicity otherwise.

There are some special circumstances, where pure oxygen can be used, such as treating a diver suffering from decompression sickness.

Read on to learn about various reasons why pure oxygen isn’t used in the scuba tank, under what circumstances it is appropriate and safe, and other information related to the topic.

Can You Dive on 100% Oxygen?

scuba diving with pure oxygen

The main purpose of a scuba tank is to replicate the experience of breathing the air we breathe on land, underwater. The air we breathe isn’t pure oxygen though, but a mixture of gases, including 21% oxygen, 78% nitrogen and small amounts of other gases.

This is the scientific reason why it’s practically impossible to dive on 100% oxygen, especially in a depth greater than 20 ft – it’s much beyond what the human body can handle and may cause health issues such as nausea, vomiting, and even drowning.

You do have various mixes of gases used in scuba tanks for various scenarios, with increased or decreased quantities of oxygen or nitrogen, but 100% O2 is never used for normal circumstances.

Why Do Scuba Divers Never Use 100% Oxygen in Tank?

Apart from the scientific aspect we’ve discussed and the health risk behind it, there is another big reason why scuba divers never use 100% oxygen in the tanks, and that is, cost.

The scuba equipment includes the compressor, which uses the air we breathe every day, and removes pollution and contaminants from it, thereby just pumping it into the tank. Because air is readily available, it is very cost-effective to just use compressed air rather than using pure oxygen, which is expensive since it requires a lot of other technical factors to be fulfilled.

In order to use pure oxygen, you need special equipment such as oxygen generators, large oxygen tanks and a regulator to be able to safely dive on 100% oxygen for extended periods of time. All these processes are costly and basically, unnecessary for recreational diving.

You’re better off just using compressed air for that.

What is Oxygen Toxicity?

Central nervous system (CNS) oxygen toxicity is a health risk associated with breathing pure O2 in depths greater than 13 feet or 4 meters. It can cause health risks such as dizziness, convulsions, blurry sight and in worst cases, drowning. The higher the concentration of oxygen, the shallower would it be safe to breathe by the diver underwater.

It’s not so much about the cost of using pure oxygen in scuba tanks – the health risks associated with it are so high that it is avoided in recreational diving and only considered for special circumstances such as technical diving or when first-aid is required.

The depth of 13 ft is very shallow anyway, and can be easily exceeded, making it even more impractical to use pure O2.

Is it Possible To Just Use More Oxygen Instead?

scuba diving oxygen toxicity

Yes, and this is what is usually done. Using 100% oxygen is unsuitable for normal circumstances, but there are various gas mixes used in scuba tanks in order to make it possible to dive deeper and longer.

The thing is, decreasing the percentage of nitrogen makes it easy to dive deeper and longer without having to go through health risks such as decompression sickness. This is where gas mixes such as nitrox and trimix come to play.

Nitrox, for instance, has a lower nitrogen content but a higher oxygen content, making it possible to dive for longer. It isn’t the ideal solution when deep sea diving though, because increasing oxygen also increases the risk of oxygen toxicity, which makes it a double-edged sword.

Trimix is a safer option, and what makes it safer is the fact that while decreasing nitrogen, it adds a third gas to the mix (that’s where the name tri-mix stems from) – helium. Being an inert gas, helium decreases the risk of various health problems such as nitrogen narcosis and decompression sickness.

How Deep Can You Dive on Pure Oxygen?

On pure oxygen, you can dive in water as long as you are within 13ft / 4m from the surface, and even for that you need special equipment such as regulators and a dive computer.

This is similar to how oxygen is sometimes used in hospitals to save patients in life-threatening circumstances. It is carried out by health professionals and for specific periods of time – any longer exposure to it can cause health risks even on land.

Under What Circumstances Can Pure Oxygen Be Used in Scuba Diving

The most common situation is where a diver is suffering from the bends – pure oxygen is provided to them so that they have sufficient air to be able to survive.

It is supplied by health professionals of the crew in case of such emergencies. It doesn’t really serve as a final solution per se – it is a temporary solution to save the diver from life-threatening health risks and increase their chances of a full recovery later on.

It is important to note if there are risks and injuries that are more life-threatening, they are treated first, and then oxygen is provided in order to alleviate decompression sickness.

Apart from being used as a first-aid tool, gas mixes with high concentrations of oxygen are also used in technical diving, in which trained technical divers basically need to speed up decompression and extend the depth at which they can dive.

The conclusion is that pure oxygen can be used by scuba divers, but only in certain justifiable scenarios.

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