Tuesday, 01 August 2000 00:00

Beyond Nitrox or "Where do we go from here?"

By Richard Taylor TDI Australia

You've done your Open Water course, your Advanced Open Water and now your Nitrox Course! You read every page of Scuba Diver, are up to date with the latest in dive gear, dive wear and dive destinations. So what's next and what is all this fuss about Technical Diving?

Rob Palmer, a pioneering Technical & Cave Diver in the UK, defined Technical Diving as "..the use of advanced and specialised equipment and techniques enabling divers to gain access to depth, dive time and specific underwater environments more safely than might otherwise be possible." Sounds exciting, doesn't it? Well it is, and the training is available now!

Part 1

There are a variety of courses offered by the Technical Training Agencies such as ANDI, IANTD and TDI. Even the traditional recreational agencies such as PADI, SSI & NAUI are moving into Technical Diving. Who knows, one day you may get a PADI or SSI Trimix Rebreather Specialty??

But, after your introduction to Nitrox, you need to decide what continuing courses are for you. So, where to go from here?

Advanced Nitrox
This course is designed to build upon the basic information introduced in the Nitrox Course. Typically you would learn about the more complex factors that need to be considered when using a variety of nitrox mixes. You could expect to be shown how to safely plan and execute a Nitrox dive using two nitrox mixes and then undertake at least four Nitrox dives, usually to a maximum depth of 45m.

The Nitrox mixtures used include those over 40% oxygen, often up to 100% oxygen (as opposed to between 21%-40% oxygen discussed during the basic nitrox course). Multiple CNS Toxicity Percentage Tracking, the Oxygen Clock and oxygen safeguards and procedures are looked at. Though no actual in-water skills may be covered except the checking of basic diving skills the use of a small stage cylinder, or pony bottle, may be covered, as may the use of doubles or twin cylinders, depending upon the agency training standards.

The prerequisites (depending on the certificate being awarded) are Advanced Diver or Open Water Diver with 20 Open Water Dives. The cost is usually between $350 and $450 and is usually run over one weekend. Often this course is combined with a Decompression Procedures or Deep Air course, allowing the diver to use the richer nitrox mix as a decompression gas.

Decompression Procedures, Advanced Deep Air, Technical SafeAir User:
Called different names by the different training agencies this course is designed to introduce you to the fundamental concepts of decompression diving. The planning and undertaking of a staged decompression diveng and the use of the extra equipment needed is covered, usually to a depth of around between 40 to 50m.

Typically equipment requirements and safety procedures are covered, and often this course is used to introduce divers to the use of doubles, or twin cylinders. Drift decompression using a reel & surface marker buoy, dual regulator, manifold use and gas management are usually covered and you will often practice gas bailouts, narcosis assessments and problem solving whilst at depth.

The redundancy ethic is introduced, requiring an increased acceptance by divers of their personal risk. Usually four dives will be undertaken and you may use Nitrox mixtures for safety whilst on decompression if this course is combined with a Nitrox or Advanced Nitrox program. The prerequisites are usually recreational Deep Air or even a Nitrox certification, but you will require practical diving experience, say 50-100 dives with some over 30m. The cost is usually $450 to $550 depending on the course and dives, and is usually conducted over two or three weekends with possibly some mid-week lectures.

Extended Range, Technical Safeair or Technical Nitrox
This course is designed to introduce the concepts of using Nitrox as a decompression gas for deeper or longer dives, using air as the primary deep gas. The use of a stage or sling cylinder for carrying the Nitrox decompression mixture is taught as well as procedures for planning and undertaking extended decompression dives at a depth of around 50m to 60m.

Somewhere between four and eight dives may be included using Nitrox mixtures ranging anywhere from 50% to 80% oxygen for decompression. Some courses use a very low Nitrox mix (say 28%) for the main part of the dive while still requiring the use of the high Nitrox mixture during ascent.

The prerequisites are usually an Advanced Nitrox or Technical SafeAir certificate and a Deep Air or Decompression Diver with at least 100 logged dives including around 20 deeper than 40m. These prerequisites will vary depending upon the course and the diver's experience. The cost is anywhere from $550 to $750 depending upon the course and dives, and is usually conducted over two or three weekends with possibly some mid-week lectures.

Part 2

Entry Level Trimix
This is an introduction to helium based diving down to a depth of 60m using nitrox for decompression. In many ways this is similar to Extended Range (Technical Nitrox) but incorporates helium to reduce the effects of nitrogen whilst undertaking dives beyond 40m.

Usually 4 to 6 dives will be included and the Trimix may often contain 21% and only a small amount of helium, say 20%. Decompression is often undertaken with a mid range Nitrox mix, say 50% - 60% oxygen.

The prerequisites are often Decompression Procedures and Advanced Nitrox, though some courses may also require a Technical Nitrox certification. The cost is similar to Extended Range, though the addition of helium adds another $50-75 per mix dive, so around $750 to $900, again over two or three weekends.

Advanced Trimix Diver
This should not be promoted as a dive course to attract students but rather should be run when a diver, with suitable experience and knowledge, wishes to dive to depths beyond the range of air. This is the top technical course offered, with an increased level of risk and is definitely not for everyone.

The Trimix Diver course is designed to introduce the diver to deep diving Helium-based breathing procedures. Advanced decompression procedures and calculations are taught as is a substantial amount of diver physiology and the need for an appropriate attitude. A high level of self planning and responsibility is stressed as is the need for additional equipment and redundancy. You would expect usually four or six (sometimes more) dives, most using Trimix and two different decompression Nitrox mixtures to depths between 60m and 80m.

The prerequisites are typically Extended Range or Technical Nitrox or Technical Safeair with a minimum of 200 dives including around 50 deeper than 50m. Again, these prerequisites will vary according to the agency, and instructor. The cost is in excess of $600 plus gas and usually works out to around $1200 to $1400 depending on the dives. Trimix courses usually require four to eight weekends to complete with possibly some mid-week lectures.

Rebreather Diver
This course is designed to give the student a basic understanding of the use and applications of the specific model of rebreather used on the course. Currently each potential rebreather manufacturer is requesting a model-specific training program. You would be introduced to the design, function and components of a rebreather, which should usually include the preparation and cleaning of the unit. The concept of varying partial pressures depending on breathing rate is taught as well as rebreather dive planning and possible system malfunctions.

Both the benefits of using and any special considerations would be discussed. Diver self-monitoring is an important aspect. Expect between six dives and eight with problem management, such as bailing out to traditional open circuit scuba, and buoyancy being strongly emphasized.

The prerequisites are both a Nitrox and Advanced Open Water certificate with around 100 dives. Some agencies will require a certain number of Nitrox dives. The cost is around $700 to $800 for Semi-Closed systems and $900 to $1000 for Closed Circuit systems, depending on the unit used and the number of dives. Rebreather courses usually run over two or three weekends with possibly some mid-week lectures.

Overhead Environment (or Cavern/Sinkhole)
This course is designed to introduce the student to the concept of diving in restricted spaces where you are unable to ascend directly to the surface and to the use of a diving reel. It should be stressed that this is an introduction to the overhead environment. Further training in advanced penetration skills should be sought if that is the intended direction of the student.

You should expect to cover sessions on the hazards of both the cavern and wreck environments. Low visibility problems including anti-silting techniques, light sources, signals and problem management should be covered as well as the extra equipment requirements and extra psychological stress which may be encountered. Line laying and following, emergency out-of-air and loss of visibility situations should be taught as well as basic cave/site etiquette. Equipment configuration and redundancy should also be covered.

The prerequisites are usually an Advanced Open Water certificate, but if the diver wishes to undertake some initial wreck penetration, then a Wreck Diving Specialty may also be required. The cost is typically $300 to $500 depending on the dives and certification undertaken and usually runs over two weekends with possibly some mid-week lectures.

You Say You Want More?
There are other courses designed to introduce the diver to either more advanced diving skills or to an 'off shoot' of the technical environment. Courses in Advanced Wreck Penetration, Cave and Sump Penetration are specific to the environment for which the training is undertaken and will develop skills in guideline use along with problem management. Courses in Gas Blending and Oxygen Service enable dive store employees (and interested divers), to gain the knowledge and necessary skills for safely mixing Nitrox and Trimix gas as well as servicing equipment suitable for use with Nitrox and Oxygen.

Get Where You Want to Go.
Overall, Technical Diving offers a safe and exciting way to develop new skills allowing you to safely execute dives you might not otherwise undertake. As I have outlined above, not all the courses are for everyone, and completing all the courses does not make you a good diver, Technical or otherwise. A good skill base, plenty of practice, experience and the right attitude are the most important factors when undertaking any type of diving. Technical Diving just helps you get to where you want go ... safely.

Richard Taylor is an Instructor Trainer in Trimix, Semi-Closed Rebreather and Overhead Environment with TDI and is the Director of TDI in Australia & New Zealand. Contact details are phone 0500 834 269 (outside Australia call +61 500 834 269), fax +61 (02) 9958 3795, email: .

Who Teaches Technical Diving?

ANDI Australia
American Nitrox Divers International (Australia)
10 Belgrave Street
Tel: (02) 9976 3297
Fax: (02) 9977 3664

IANTD (Australasia)
International Association of Nitrox and Technical Divers (Australasia)

TDI Australia & New Zealand
Technical Diving International
PO Box 894
Te00 834 269
Fax: (02) 9958 3795