Hydreliox – A Deep Diving Breathing Gas


Hydreliox is a specialized breathing gas mixture that contains hydrogen, helium, and oxygen. This blend is specifically designed for deep diving applications where divers must descend to extreme depths. As a result, it is particularly useful for scientific, commercial, and technical divers working in challenging underwater environments. Hydreliox has several key properties that make it advantageous over traditional breathing gas mixtures, such as decreased narcotic effects, reduced work of breathing, and minimized decompression times. This article will explore the composition, benefits, and limitations of Hydreliox as a deep diving breathing gas.


Hydreliox is a carefully formulated mixture of three gases:

  1. Hydrogen: The lightest element and most abundant in the universe, hydrogen accounts for 49% of Hydreliox. Its low density and molecular weight contribute to reduced breathing resistance at depth.
  2. Helium: This noble gas makes up 50% of the Hydreliox mixture. It is known for its low solubility in tissues, making it a preferred gas for minimizing decompression-related complications. Additionally, its low density reduces the work of breathing.
  3. Oxygen: The remaining 1% of the mixture is oxygen, which is essential for maintaining life and facilitating metabolism in the human body. It is carefully monitored and adjusted to maintain a safe partial pressure for divers at depth.


Hydreliox offers several advantages over conventional breathing gas mixtures like air, nitrox, and trimix. These benefits include:

  1. Reduced Narcotic Effects: Hydrogen and helium both have lower narcotic potentials than nitrogen, which is the primary constituent of air. This means that Hydreliox has a significantly reduced risk of nitrogen narcosis, a condition that can impair a diver’s cognitive function and decision-making abilities at depth.
  2. Lower Work of Breathing: The low density of hydrogen and helium significantly decreases the work of breathing, especially at great depths. This reduced resistance helps divers maintain their physical performance and conserve energy during long and challenging dives.
  3. Minimized Decompression Times: Helium’s low solubility in human tissues allows for faster off-gassing during decompression, reducing the time needed for divers to ascend safely. This aspect is crucial for deep divers, as extended decompression times can lead to increased risks of decompression sickness and other complications.
  4. Enhanced Thermal Insulation: Due to its low thermal conductivity, helium provides better insulation against the cold, helping divers maintain their body temperature during extended exposure to cold water environments.

Limitations and Considerations

Despite its benefits, Hydreliox also presents several challenges and limitations:

  1. Flammability: The presence of hydrogen, which is highly flammable, raises concerns about the potential for fires and explosions. However, this risk is mitigated by careful gas blending and strict safety protocols, ensuring that the hydrogen concentration remains below the lower explosive limit.
  2. Availability and Cost: Hydreliox is more expensive and less readily available than other diving gases due to the cost of production and the specialized equipment required for blending and storage. This factor may limit its use to specific applications or well-funded diving operations.
  3. Specialized Equipment: Divers using Hydreliox must have access to specialized diving equipment, such as regulators and cylinders designed to handle the gas mixture. Additionally, they must undergo thorough training in handling and using this unique breathing gas.
  4. Voice Distortion: The presence of helium in Hydreliox causes divers’ voices to become distorted and higher pitched, which can make communication challenging. Specialized underwater communication systems can help mitigate this issue.


Hydreliox is a unique and innovative breathing gas mixture that offers significant

advantages for deep diving applications. Its reduced narcotic effects, lower work of breathing, minimized decompression times, and enhanced thermal insulation make it a valuable asset for divers operating in extreme underwater environments. However, its use also presents certain challenges, such as flammability concerns, availability and cost, specialized equipment requirements, and voice distortion.

As a specialized breathing gas, Hydreliox has found applications in various deep diving fields, including underwater research, marine archaeology, salvage operations, and commercial diving. Its unique properties have allowed divers to reach depths and durations previously unattainable using conventional gas mixtures, opening up new possibilities for scientific discoveries and underwater exploration.

To ensure safe and effective use of Hydreliox, divers must undergo comprehensive training and certification. This education encompasses not only the technical aspects of diving with Hydreliox but also the physiological understanding of how the gas mixture interacts with the human body at depth. Additionally, divers must be well-versed in the specific safety protocols associated with handling and using hydrogen-based gas mixtures.

The development and application of Hydreliox as a deep diving breathing gas showcase the advancements in diving technology and the continuous efforts to push the boundaries of human exploration in the underwater world. As further research and innovation continue, it is likely that even more advanced and specialized gas mixtures will be developed, enabling divers to reach even greater depths and overcome new challenges in the underwater realm.

In conclusion, Hydreliox has proven to be a game-changer for deep diving operations, enabling divers to reach depths previously thought impossible or highly dangerous with traditional gas mixtures. Its unique combination of hydrogen, helium, and oxygen offers numerous benefits while also presenting certain challenges that must be managed effectively. As diving technology and research continue to evolve, Hydreliox and other innovative breathing gas mixtures will play a critical role in unlocking the full potential of human exploration in the underwater world.