Nitrox in recreational diving

14/06/2021

In the world of diving it is not strange to hear about Nitrox, Enriched Air or EAN. However, do you know what it is and what uses it has?

We will briefly explain it to you below.

What is Nitrox?

In general, when diving we say that the air contains 21% Oxygen and 79% Nitrogen.

In the case of Nitrox, also called EANx or enriched air, the concentrations of these gases vary, with an increase in the concentration of Oxygen, which leads to a decrease in Nitrogen. In this way we can obtain various mixtures. The most common in recreational diving are:

  • EAN 32: contains 32% Oxygen and 68% Nitrogen
  • EAN 36: contains 36% Oxygen and 64% Nitrogen
Nitrox mixes

Why do we use Nitrox?

One of the main limiting factors in recreational diving is the No Decompression Limit, which is determined by the amount of nitrogen present in the body. By using EANx we decrease the amount of this gas breathed, increasing the no-stop time, which means that we can do longer dives.

In addition, the effort made by the body to expel Nitrogen after a dive causes us a state of fatigue. This is also reduced when we use enriched air.

Nitrox diver

What are the differences in the usage procedures?

When diving, procedures and equipment do not change from when diving with normal air. However, this is only valid for mixtures of up to 40% oxygen, which is the maximum allowed in recreational diving.

The only difference is the need to do 3 steps before diving with this type of gas. These steps must always be carried out personally. They are:

  • Analysis of the tank: before diving we must make sure we know the percentage of oxygen in the tank that we are going to use. This is checked by means of specific analyzers that are placed in the gas outlet of the bottle while a small amount of gas is allowed to flow to the outside.
  • Computer configuration: once the mixture has been verified, the computer must be configured to mark the specific depth limits for that percentage.
  • Fill in the forms: when you dive with Nitrox you must sign some papers in which you state that you have analyzed the bottle and you know the percentage of oxygen it contains and the maximum depth that you can reach with that value.

Another consideration to take into account is that the bottles used for this type of gases must be correctly marked. They usually have a green and yellow sticker on the body of the bottle where it says: Nitrox, Enriched Air or EAN.

Nitrox

Considerations when diving with Nitrox

The greatest risk of diving with enriched air is hyperoxia. This occurs from a depth determined by the percentage of oxygen present in the mixture you are using. A partial pressure of 1.4 bar in recreational diving has been set as the limit for Nitrox diving. For instance:

  • With EAN 32: 1.4 / 0.32 = 4.4 bar approximately. This pressure is reached at a depth of 34 meters, therefore that will be the maximum depth.
  • With EAN 36: 1.4 / 0.36 = 3.9 bar. Pressure that is reached at 29 meters, which will be the depth limit.

The biggest danger in exceeding the specific limit for the gas we are breathing is that you can have seizures. These aren’t dangerous in and of themselves, but they often cause you to spit out the regulator, knocking you out of air for several minutes.

Nitrox table

Another characteristic to take into account when using enriched air is the risk of fire, due to the high combustion capacity of O2. This risk is not very high with concentrations lower than 40% of oxygen, for this reason in recreational diving this is the maximum percentage used.

Due to this considerations, to dive with Nitrox it is necessary to take a specific course, such as the PADI Enriched Air Diver, in which we teach you the correct handling of these gases.

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