up to Adv. Trimix with END 30 m

[ElBacio]

Hello,

Two potential students asked me if it is possible to go through the education ladder at TDI from Nitrox to Adv. Trimix while keeping END below 30m. (The limit comes from their existing DIR training and philosophy).

I looked at the standards:

Nitrox - no problem to do the course while keeping END below 30m
Adv. Nitrox - no problem to do the course while keeping END below 30m
Decompression Procedures - at least two dives must be below 30m on air (!)
Extended Range - at least two dives must be below 40m on air (!) and four dives below 30m (!)
Trimix - at least two dives must be below 40m, but with the proper TMX mix END could be kept below 30m
Adv. Trimix - at least two dives must be below 70m, but with the proper TMX mix END could be kept below 30m

According to the standards, the Extended Range course could be skipped if the (basic) Trimix course is in the list of to do.

If I am right, the only legal problem would be Decompression Procedures course, where the student must go below END 30m and this course cannot be skipped.

Is there any way to do the course according to the standards, while fulfil the student's philosophy of not going deeper than END 30m.
If not, would Agency issue a waiver if he applies for the instructor at Decompression Procedures Course not to go below 30m on the course, but reach only 30,0m.

El Bacio

 

[Steve SDI/TDI HQ]

Number One: Extended Range is certainly NOT a requirement in your student's path through TDI's curriculum; so disregard it completely.

With regards keeping the END to 30 metres or less during their trimix training, my personal modus operandi is to set 30 metres as the maximu; so that's no problem.

Decompression procedures does, as you have identified, stipulate that two dives should be deeper than 30 metres. It does not say how much deeper and therefore 30.1 would meet requirements according to the 'letter of the law.' Given the vagaries of the instruments we wear to gauge depth, it seems silly to allow divers to think that 29.9 metres is OK and 30.9 is not.

However, depth is not just about narcosis. Situational Awareness is influenced by many factors and its management, a key tool for technical diving, demands many more things besides tracking the partial pressure of nitrogen. Please do not allow your students to fall into the trap that with an END of 30 metres or less, SA is taken care of. Deviation from focus seems to begin for many divers as soon as their heads go underwater. In addition, you will have to spend considerable time at 30 metres to earn an appreciable decompression obligation during their deco class. While it is certainly and clearly not necessary to have students at this level function under an onerous decompression obligation, there are some psychological stressors that you must look for in your charges; and these tend to show themselves only under the shadow of a 'real decompression situation' rather than a pretend one.

Hope that answers your questions.