divingis a sport that requires not only a lot of preparation, but also a lot of control over the equipment that is going to be used. We cannot forget that underwater we also have to breathe!

Reasons for using mixed gases in diving

What can motivate us to breathe mixtures other than air if our body is perfectly adapted to breathing air from the moment we are born? Well, this is not exactly true. Our body is adapted to breathe air at atmospheric pressure, but when we breathe it at high pressures, in the case of diving, the air leaves of being the best gas that we can breathe.

Know the reasons for mixing gases in diving


If we consider the mixture of breathed gases as any other element of our diving equipment, we will try to make this mixture optimal for the type of dive we are going to practice.

Why is air not an optimal mixture?

  • It has too much nitrogen, which forces us to limit our diving time or make decompression stops in order to eliminate the excess of this gas accumulated in our tissues. li>
  • Below -30 meters the air begins to be narcotic, it reduces our ability to think and makes it very difficult for us to carry out minimally complex tasks.
  • Below -40 meters the effect of the increase in ambient pressure causes a high density of the breathed air, which considerably increases and difficults the respiratory work, which can lead to a feeling of suffocation.
  • Below -66 meters the air begins to be clearly toxic due to the high partial pressure of oxygen.


Practice with nitrox


So, what other gases other than air can we count on to breathe?

Main types of gas mixtures

  • Superoxygenated mixtures, called nitrox or enriched air. To reduce the amount of nitrogen and be able to lengthen diving times without increasing the need for decompression, or as a decompression gas, to accelerate decompression.
  • Mixtures with helium. To reduce nitrogen narcosis, oxygen toxicity and to decrease gas density breathed Also recently and experimentally, mixtures with helium are beginning to be used for decompression. Mixtures with helium have different names, heliox (helium + oxygen) and trimix (helium + oxygen + nitrogen).

Likewise, some trimix mixtures are called by other names such as heliair, which is known as a particular type of trimix mixtures, obtained by mixing helium with air. and, recently, mixtures obtained with helium + nitrox are also beginning to be called helitrox.

In addition, two other gases are used, 100% oxygen for decompression stops of -6 m and -3 m and, occasionally, argon, not as a breathing gas, but as insulating gas to inflate dry suits.

Point out the air cylinders to have them identified

Differences between diving with mixtures and diving with air

In recreational diving, nitrox mixtures with oxygen content between 21 and 40%:

  • Material: all diving equipment can be the same as in air diving, we will only have to adapt the decompression tables or use specific ones, or have a diving computer with a nitrox function. Nitrox bottles must be perfectly marked as NITROX.
  • Before the dive: you must make sure of the oxygen content in the mixture, as well as the maximum depth at which you can breathe and clearly note that depth on the bottle.
  • During diving: with respect to diving with air we only have to be careful not to exceed the maximum depth of the mixture.
  • Decompression: Diving times without the need for stops will be significantly increased, or decompression times reduced. For example, if we do not want to go into decompression, with nitrox 36 (36% oxygen) we can stay 35 minutes at 28 meters, while with air we can only stay 25 minutes. With nitrox 36 we gain 40% bottom time without decompression.
  • After the dive: we must keep in mind that there is no air in our bottle and that, if it is reused by third parties, they must be informed of this.

In sport diving with mixtures, below -40 meters, the differences with respect to diving with air They are numerous and will be discussed in future articles, but basically we can highlight three differences:

  • Different mixtures are used during the same dive, which requires carrying several bottles. Descent mix, bottom mix, decompression mix...
  • When carrying more material, you must use equipment different from that usual in recreational diving that allows you to carry this new material in a simple and effective way.
  • Dive planning takes on a very important role, hence the phrase, "plan your dive and dive your plan."

Practice the necessary diving techniques

Where to get training in mixture diving?

Recreational diving with nitrox mixtures is very widespread today, practically all diving teaching organizations that operate in Spain, such as PADI, SSIo FEDAS , they havenitrox training programs and you can access these coursesstarting at an intermediate level of air diving (two stars or advanced courses from different organizations).

Beyond the limits of recreational diving, in Spain this training is only contemplated by two foreign organizations (IANTD: International Association of Nitrox and Technical Divers) and TDI (Technical Divers International) with numerous levels and specialties. Outside our country there is also another highly prestigious organization, GUE (Global Underwater Explorers), dedicated to speleodiving and mixture diving training.