Advanced Nitrox

[DevonDiver]

The DSAT Apprentic Tec course appears to teach "multiple gas, extended no stop" dives. I interpret this as meaning that you would plan a multilevel dive using one gas at one depth, and another gas shallower.

The ability to plan and conduct multi-level, mixed gas dives and stay within recreational NDLs would be a benefit that came with any Advanced Nitrox course.

To do diving like this, you need the following training components:

1. Gas Switching.
2. Dive planning (including gas planning)
3. Understanding of Nitrox (40-100%)

These are common of every entry-level tech course, regardless of agency or the name applied to the course.

What this means to the diver is that, following the course, they can gain experience in mixed-gas diving, gas switching and dive planning, without exceeding their training and entering the realms of staged decompression diving (which comes in subsequent DSAT courses - as it does with every tech agency).

This could mean a set of indie doubles with mixes like Air+36% or a back gas of 32% with a 40% stage. Quite useful really...and does open up some options within recreational depth limits.

You may find a instructor who would teach TDI Advanced Nitrox in this way. But put yourself in the situation where you are still at depth, and for some reason your backgas runs out - how tempting is it to switch to a higher O2 (ppO2 >1/6) mix? I personally don't like the idea of "multigas extended no stop" diving. The DSAT syllabus is not overly well thought out, to be honest.

This is quite a pathetic point to make.

Running out of gas? This would apply to any situation in technical diving. IF you ran out of backgas, and had no air-sharing options, then the temptation to breath from an inappropriate mix would always exist. The same point could be made of am Advanced Nitrox or Trimix diver....

Remember, the 'Apprentice Tech' (Tech 1) is a TECHNICAL DIVING course... so any, such qualified, divers would also have recieved the appriopriate training and practice in properly planning their dives, including gas management and team/buddy safety drills.

As for "multigas extended no stop" diving - then this is simply the most efficient way to maximise your bottom time within recreational limits. All of the benefits of basic nitrox, plus multi-level....with the added benefit of gas switching....and the refinement of tech standard dive planning, gas managment and equipment configurations.

I think there is a large number of divers out there who use tech configurations and additional air supplies for recreational diving.... so this just underpins that type of diving with some good training.

You'll get a lot more out of doing a full tech class (e.g. Adv. Nitrox & Deco. Proc.) and then you can tailor your diving in light of the knowledge you'd gain in the course.

The "full tech class" you mention is several courses...in the same way that DSAT offer several courses...a modular approach...where the end result of those courses is the same (extended range, accelerated deco).

In actual fact, DSAT is currently re-vamping the tech program. see HERE. The future structure will be...

Diver Levels


Tec 40
The entry point into the technical range, it provides a transition from recreational to tech. Although the use of full tech gear (doubles and wings) is preferred, it does allow modified use of recreational gear in some situations, provided the diver has two separate regulators, with one of the first stages fitted with a long hose. The intended working limit for a diver of this grade is 40 metres/130 feet with up to 10 minutes of non-accelerated decompression while breathing up to EANx50.


Tec 45
The diver now must wear the full ‘standardised’ tech rig, including wings and doubles, plus an additional deco cylinder. (Note that side mounted cylinders are an acceptable alternative to back mounted doubles throughout the TecRec range). The course will allow the diver to go to 45 metres/145 feet and make accelerated decompression dives using any mix of EANx or oxygen.


Tec 50
At the end of this course the diver will have the same set of skills and knowledge as the present Tec Deep Diver. As such it represents a high level of competency for a technical diver. Although the option exists to make the last dive of the course using trimix, it is intended as an air/nitrox rating and by the end the diver can dive to a maximum of 50 metres/165 feet and make extended, accelerated decompression dives.

[ianr33]

The ability to plan and conduct multi-level, mixed gas dives and stay within recreational NDLs would be a benefit that came with any Advanced Nitrox course.

Sure. But whats the point? Why not just do a deco dive and be done with it?

What are they going to call the "Tec 40" course in the USA?

[Blackwood]

The ability to plan and conduct multi-level, mixed gas dives and stay within recreational NDLs would be a benefit that came with any Advanced Nitrox course.

The ability to plan and conduct multi-level, mixed gas dives and stay within recreational NDLs would be a benefit that came with any Basic Nitrox course.

[dori fish]

Question: If not able to do deco or don't want to, what is the benefit of advanced nitrox?

[ianr33]

Question: If not able to do deco or don't want to, what is the benefit of advanced nitrox?

Knowledge of deco theory. Practical experience using doubles. Otherwise not much

[DevonDiver]

The ability to plan and conduct multi-level, mixed gas dives and stay within recreational NDLs would be a benefit that came with any Basic Nitrox course.

Incorrect. No basic Nitrox courses allows you to dive with mixed gas. 'Mixed gas', does not mean that you have a blended mix (i.e. nitrox) in your tank.... but that you will use a mix of different gases during the conduct of your dive. i.e. you will change the gas that you are breathing mid-dive.

No basic level nitrox course will teach gas-switching procedures and, therefore, will not prepare or qualify you to conduct a dive with more than one mix at your disposal.

Question: If not able to do deco or don't want to, what is the benefit of advanced nitrox?

To prevent entering into formal decompression obligation, by using multiple gases, of the appropriate percentage O2 for the planned levels of the dive.

A basic nitrox course allows you to select a single gas to conduct a dive...and that gas is normally optimized for the greatest benefit at the deepest planned depth. You may then choose to calculate a multi-level profile to further extend your bottom time - but you continue to use the same gas (which is less optimal as you rise from your maximum depth and ascend levels.

An advanced nitrox course, enables you to select two or more gases, where each gas is optimal for the depth at each planned level of you dive.

However, few divers have a need for such long duration dives....and, in reality, the advanced nitrox courses tends to become a simple vehicle for ingraining the basic equipment familarity and drills required in later stages of tech training, whilst also developing the theoretical knowledge required to underpin the decompression dive planning and deco theory that comes later with decompression procedures and extended range courses.

In short, Advanced Nitrox, is most beneficial as a foundational tech course, providing the basic drills and theoretical understanding needed to start decompression diving training.

[Blackwood]

Incorrect. No basic Nitrox courses allows you to dive with mixed gas. 'Mixed gas', does not mean that you have a blended mix (i.e. nitrox) in your tank.... but that you will use a mix of different gases during the conduct of your dive. i.e. you will change the gas that you are breathing mid-dive.

Interesting. I've never thought of "mixed gas" diving as being "gas switch diving."

(In other words I've always used mixed gas to mean anything other than air)

To prevent entering into formal decompression obligation, by using multiple gases, of the appropriate percentage O2 for the planned levels of the dive.

If a decompression gas is required in order to allow a direct ascent (at 30fpm or 60fpm or whatever the associated 'NDL' model assumes), how is that not 'formal decompression'?

[Steve, SDI/TDI HQ]

Question: If not able to do deco or don't want to, what is the benefit of advanced nitrox?

Somewhat marginal on general open circuit dives... very useful tool to divers harvesting shellfish and doing scientific work at shallow depths.

We usually see this taught in conjunction with decompression procedures, but keep it as a stand-alone course mostly for folks doing CCR diving (closed circuit rebreather).

Knowledge of deco theory. Practical experience using doubles. Otherwise not much

Neither of these nuggets are covered in an our advanced nitrox course... certainly NOT decompression theory.

[ianr33]

Hi Steve. I'm sure you know much more about it than I do,but the first time I used doubles was on my Advanced Nitrox/Deco course. Went over loads of VPM,RGBM,Gradient Factors etc. Maybe that would not have been included in Advanced Nitrox on its own??

[peterbj7]

I'm not sure about the TDI course, because although I did all of them through to advanced trimix it's a long time ago. But with IANTD you certainly do use doubles and learn a lot of theory.