Thailand – Australia – United Kingdom

Mixed Gas Trimix Diving Tek Course

Koh Tao, Thailand

Big Blue Tech – Technical Diving Thailand – Celebrates the graduation of Buddhi De Silva Wickramanayake from his TDI Trimix Diver Course and Rodney Gibbs completes his TDI Trimix Instructor Course with TDI Trimix Range Instructor Trainer Ben Reymenants during a week long scuba diving workshop and deep technical diving session off the coast of Thailand on Koh Tao Island.

The term “mixed-gas diving” refers to any activity in which the diver breathes a mixture other than air or nitrox. The main incentive to dive with “non-air” gas mixtures is to avoid nitrogen narcosis. Mixed-gas diving can also be beneficial in improving decompression and avoiding oxygen toxicity. Mixed-gas diving operations require detailed planning, sophisticated equipment and, at times, extensive support personnel and facilities. The fact that such dives are often conducted at great depths and for extended periods of time increases the risks associated with them. It is extremely important for the breathing mixture to be properly identified, because breathing the wrong mix can lead to a fatal accident.

One type of mixed gas diving involves the use of heliox. This (helium 79% and oxygen 21%) mixture is often used for very deep diving. Unlike nitrogen, helium is not known to have an intoxicating effect at any depth; it has a lower density than nitrogen, making it easier to breathe; and in cases of extended submersion, it improves decompression. Still, heliox has its drawbacks. It is expensive, has a limited availability, and its thermal conductivity is six times greater than that of nitrogen. This means that a diver breathing heliox will lose body heat six times faster than someone breathing compressed air or nitrox, making them susceptible to hypothermia. To prevent this, divers often wear special suits filled with hot water that is pumped down from the surface. Heating the heliox before the diver inhales it is another strategy used to combat hypothermia. Either of these procedures require specialized equipment and highly trained personnel.


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