Deep Air Technical Diving in Thailand
Narcosis, decompression, oxygen, nitrox and addrenaline a tech diver make!
Koh Tao, Thailand
Big Blue Tech celebrates the successful completion of a TDI Extended Range diver course for Ian Jordan and David Tipping by TDI Instructor James Thornton-Allan conducted over 4 days on Koh Tao Island off the coast of Thailand.
Considered by many to be the one of the most challenging experiences for the recreational technical diver, the TDI Extended Range course provides the training and experience required to competently utilise air and Nitrox for dives up to 55msw that require staged decompression.
Extending your range doesn’t necessarily mean diving “deep”, it can simply mean diving for a longer duration. Example: Performing a dive on a wreck in 30msw with a 60 minute bottom time.
This course builds on the fundamental knowledge base developed throughout the Advanced Nitrox and Decompression Procedures courses. You will perform decompression dives that require accelerated staged decompression utilising air, Nitrox and Oxygen mixtures.
One of more divisive subjects in technical diving concerns using compressed air as a breathing gas on dives below 130 feet (40 m).While mainstream training agencies still promote and teach such courses (TDI,IANTD and DSAT/PADI), a minority (NAUI Tec, GUE, UTD) argue that diving deeper on air is unacceptably risky, saying that helium mixes should be used for dives beyond a certain limit (100–130 feet (30–40 m), depending upon agency). Such courses used to be referred to as “deep air” courses, but are now commonly called “extended range” courses.
Deep air proponents base the proper depth limit of air diving upon the risk of oxygen toxicity. Accordingly, they view the limit as being the depth at which partial pressure of oxygen reaches 1.4 ATA, which occurs at about 186 feet (57 m). Helitrox/triox proponents argue that the defining risk should be nitrogen narcosis, and suggest that when the partial pressure of nitrogen reaches approximately 4.0 ATA, which occurs at about 130 feet (40 m), helium is necessary to offset the effects of the narcosis. Both sides of the community tend to present self-supporting data. Divers trained and experienced in deep air diving report less problems with narcosis than those trained and experienced in mixed gas diving trimix/heliox, although scientific evidence does not show that a diver can train to overcome any measure of narcosis at a given depth, or become tolerant of it.
Trimix/Helitrox is a popular course here at Big Blue Tech but for our students the cost of helium back home (Australia and England) made the cost of the divers far greater than the benefit. The choice to dive deep air is personal but also financial as some regions in the world have heavy tax on helium and it can also be very difficult to obtain.
The Divers Alert Network does not formally reject deep air diving per se, but indicates the additional risks involved in an article by John Lippmann, DAN. “How deep is too deep?”. http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=29.
The course covered varied degrees of difficulty from strong current, zero visibility and 4m waves. Koh Tao can be very hospitable at 18m but deeper then 30m a seemingly “cocktail” dive can become quite a challenge for even the most experienced diver.