Here's a good one for the PADI trimix instructors

[divezonescuba]

According to padi standards, the prerequisite for TEC 65 trimix is TEC 50. The prerequisite for TEC trimix is also TEC50.

But, TEC 65 trimix requires a total of 5 dives while TEC trimix only requires 3 dives. At the same time TEC trimix does not have the 65 meter limitation of TEC65 trimix. The recommended number of hour is somewhat greater for TEC trimix than for TEC65 trimix. Hopefully this implies more content to the TEC trimix course.

So, the question is, what is the purpose of taking TEC65 Trimix instead of going straight to TEC Trimix? I could understanding taking TEC65 Trimix if it was a prerequisite for TEC trimix, but it is not.

Is there an error in the standards chart?

Thanks.

 

[RainPilot]

In my case, because I want to do some (non-training) dives to 65m before I go down to 90? YMMV

 

[boulderjohn]

PADI trimix is designed to be one course with 8 dives. Those 8 dives get progressively deeper. When you complete the 5th dive, you have completed the Tec 65 requirements. If you wish, you can stop there, but there is no requirement that you stop along the way to get that card. The only times I have issued Tec 65 certifications were for divers who had some good reason to stop temporarily and needed a card so they could do some dives at that level. The others just completed the full trimix certification.

Why would you stop? In each case it was scheduling. It can be tough to get all those dives done in a short time span.

 

[RainPilot]

So out of curiosity, if I had Tec50 could I just do 3 dives to get Trimix, or would it be "3 if you have Tmx65 else 8"?

 

[boulderjohn]

So out of curiosity, if I had Tec50 could I just do 3 dives to get Trimix, or would it be "3 if you have Tmx65 else 8"?

There are 8 dives required for full trimix, and they get increasingly deeper, and there are specific skills to be covered on each dive. You can't just do any old dive and call it good--the specific dives are done in specific order and teach specific skills. The first one is very shallow and is pure skills--it can be done in a pool. (For example, you learn how to handle 4 deco bottles.) Here are the depth ranges for the remaining dives:

Dive 2 27 meters/90 feet to 50 meters/165 feet
Dive 3 30 meters/100 feet to 50 meters/165 feet
Dive 4 40 meters/130 feet to 5 meters/185 feet
Dive 5 45 meters/150 feet to 65 meters/210 feet
Dive 6 55 meters/180 feet to 70 meters/230 feet
Dive 7 65 meters/215 feet to 80 meters/265 feet
Dive 8 75 meters/245 feet to 90 meters/300 feet​

If you have Tec 50, then you have to do all 8 dives to be full trimix. If you have Tec 65, you have to do dives 6, 7, and 8. Some of the requirements repeat some Tec 50 work, so if you completed Tec 50 within the previous 6 months, you can waive those requirements.

The reason for the Tec 50 requirement is that the Deep Diver sequence (Tec 40, 45, and 50) teach information and skill which you are assumed to have mastered in the Tec Trimix course, and that instruction is not repeated in the Trimix course. If you cross over with a qualifying certification from another agency, you have to complete the knowledge through Tec 50, although you do not have to get those certifications.

As is true in all courses, the number of dives is not the key factor. You must demonstrate mastery of the required skills during those dives. For example, you will need to be able to do valve shutdown drills during decompression stops without losing control of your depth or position.

 

[RainPilot]

That makes sense to me, thanks John.

 

[divezonescuba]

So, the standards table has an error in it. It seemed to be too lax to issue the full trimix cert with only three dives to be good for 90 meters.

If you have completed TEC50 within 6 months, what requirements are waived?

Is there a time limit to only do the three additional dives after TEC65 trimix for the TEC trimix cert?

 

[DevonDiver]

John explained it quite well.

After Tec50, a diver can either opt for Tec65 or Tec Trimix.

If they opt for Tec65, they only need 3 further dives to get the full Tec Trimix.

If they opt to do the full Tec Trimix course, it's a minimum of 8 dives.

Tec65 isn't a mandatory level. It's an option.

Basically, you can either do the 8 dives as a single program or you can split them into 2 courses, with Tec65 as an interim.

Having an interim level qualification is beneficial for many students, for many reasons.

This is also why the Tec Deep syllabus was previously split into 3 stages (Tec40/45/50).

At no point can you progress from Tec50 to full trimix in 3 dives. That'd be ludicrous.

I'm not aware of a time limit (I'm not at my laptop to check the manual) for moving from Tec65 to Tec Trimix. I don't believe there is a limit.

However, it's pertinent to remember that the courses are highly performance related. For a Tec65 diver to pass Tec Trimix in 3 dives they'd need to start the course at the performance level expected of a competent Tec65 diver.

Assigning an arbitrary time limit is irrelevant. A diver may have used that time to refine and ingrain skills through active diving at that level... or they may have been idle and allowed their competency to fade post-qualification.

I'd suggest that any tech diver planning full trimix training should already understand the need to enter training with consistently reliable skills and active experience at their existing level....and that remedial dives, or failure to graduate, is a likely result from turning up unprepared and unable.