By Clare Hudson
Within a decade, technical diving has moved from being the preserve of extremists to becoming a main stream, yet specialized, field. The rationale behind technical diving has been reached only after passing through a series of challenges and scrutiny in the past. In the late 1980s the International Association of Nitrox Technical Divers became the first specialized technical training centre, marking a revolution in diving. For the recreational Scuba diver, the diving depth limit is 40m and the diver should surface directly in up an unrestricted course. However, technical divers enjoy unlimited diving depth and the diver may need to resurface along a more restricted route such as in technical cave diving. Wreck diving also challenges the diver's ability to cope with unstable conditions and the maze-like corridors in a wreck. After a deep dive, the diver's body has absorbed a large amount of inert gas (mainly nitrogen). There is a life-threatening danger in surfacing without following a proper decompression process during the ascent.
Technical diving is a relatively risky activity; therefore, the training course follows stricter rules when admitting students. The instructor has the right to refuse non-suitable candidates onto courses such as technical cave diving and re-breather diving. Generally, students participating in basic technical diving courses should have at least two to three years of diving experience, perhaps even as certified recreational diving instructors.
The main difference between technical divers and recreational divers is not their experience or courage, but their mind set. Recreational divers are happy to swim over coral and fish, while technical divers are eager to test their limits. At a depth of 300 feet, the diver's personality, clear mind and technique are under massive stress. Even a minor mistake can lead to uncontrolled results in this environment. Therefore, psychological fitness is even more important than physical fitness for a technical diver.
How should you choose a technical diving training agent? There are about five international training centres in Hong Kong, including the founding agent IANTD and PADI. Several points should be considered when selecting a training centre: equipment availability and standard, insistence on reasonable and correct training procedures, the experience of the technical diving instructors, and the opinions of ex-students. Though cost could be another point to consider, the difference of a hundred or a thousand dollars is meaningless compared with the value of your life.
The course structure of a technical diving course is similar to a recreational one in that everyone starts from a basic level, even if you are a qualified instructor or experienced diver. The technical deep dive course comprises three different levels under the IANTD and PADI systems. The basic course is named Advanced Nitrox Diver (IANTD) or Apprentice Tech Deep Diver (PADI). It teaches the student the benefits, hazards and proper procedures to dive to a 45m depth using high content oxygen for rapid decompression. This is deeper than the recreational diver's limit. It is important to strictly follow the time and safety stops procedures for surfacing, otherwise decompression sickness (the Bends) could result. If a diver spends 30mins at a depth of 45m, they will need an extra 40minutes for decompression. After finishing the basic course, the student can move on to the Technical Nitrox Diver (IANTD) or Tec-Deep Diver (PADI). In this course, the student dives as deep as 55 meters with two oxygen-rich tanks (one is pure oxygen) for decompression. The 30-minute deep dive practice at 55m will necessitate another 50 mins for decompression. Apart from the deep dive practice, the student thoroughly studies the high pressure impact on the diver and psychological changes and works on improving posture and buoyancy control technique.
The final course is Trimix Diver. The diver uses a combination of low oxygen, low nitrogen and high helium gas mixtures for an 80m dive. This gas mix is essential for such a deep dive as ordinary pressurized air places negative impacts on the diver's body at depths of more than 55m. The 21% in air after 55m depth will cause the diver to conrulse and even lose consciousness - this is oxygen toxcity. Inappropriate usage of the trimix gases, however, will also cause problems; therefore, specialized training is a must.
All the technical diving courses include lectures, pool work and deep water practice. The ratio of instructor to student is much lower than in recreational diving courses in which one instructor handles 3 to 4 students and the ratio is even stricter for certain courses, to account for the more complicated nature of the course.
Technical Diving is still a risky activity, the technique and experience learnt from technical diving can feed back into recreational diving to improve the safety standard for the whole diving industry.
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