Decompression Course

[alewar]

DuboisP or anyone else, can you specify the CMAS limits for each level of training please?

Edit: alewar, just saw your post, but can't read that table. Can you please clarify? Thanks in advance.

A CMAS* diver is supposed to stay above 21m unless he's is diving with a CMAS** instructor, in which case they can go down to 40m.
I think there is a crossover arrangement with PADI, so it wouldn't be too difficult to go from PADI OW to CMAS**.

CMAS deco is solely based on the holy Bühlmann table I posted above. What you learn is to trust that table...
You can read the table in the following way:

The big black number in each box is the depth in meters. If you have no exact match you use the next bigger number.
The smaller number below the depth is the NDL in minutes.
The blue row with the text "Stopp in" and the white numbers are the depths of the deco stops in meters.
For example, if you were to stay at 42m for 19 minutes, according to the table you have to do a 2 minutes deco stop at 9m, a 4 minutes stop at 6m and finally a 10 minutes stop at 3m. The table works with an ascend speed of 10m/min and air as a breathing gas. The letters in yellow are the groups for repetition dives in case you want to do more than one dive per day (the table has another side with that info and covers down to 60m)

While CMAS**+ divers are free to use that table the way they like up to 40m it's discouraged to go that deep.
Just think about the gas requirements if things go wrong... you don't want to go into deco with one cylinder.

 

[DuboisP]

DuboisP or anyone else, can you specify the CMAS limits for each level of training please?

I will speak for France, we have some little differences with CMAS.
Niveau 1 (CMAS Level 1) : 20 m limit, always supervised. can be autonomous at 12m, but not usual. can share his air with buddy.
Niveau 2 (CMAS Level 2) : 20 m autonomous, 40 m supervised. trained to decompression. can assist his buddy and help him to go up.
Niveau 3 : 60 m autonomous. trained for decompression. can rescue his buddy.
Niveau 4 (CMAS Level 3) : as Niveau 3. Supervisor for Niveau 1 and Niveau 2.

Nitrox (40% oxy max) can begin at Niveau 1.
Advanced Nitrox (100% oxy) can begin at Niveau 2.

We have a couple of intermediate levels since a couple of years, to allow divers to be autonomous or supervised at different depths, without having to be fully certified, as PA40 (autonomous to 40m) and to welcome other certified divers (an AOWD can be recognized as a PA40, for the example, depending the log book, or the visibility, or a check dive...)

Specialities exist, but rarely mandatory. I have not be trained to dry suit or double. For dry suit, i asked another diver to assist me a couple of dives. for double, just purchased and dove.

CCR and Trimix are another matter of training, fully tek.

I can dive to 60m with a 15L full of air.
I prefer to have my double and my oxy pony

in french Polynesia and some other autonomous territories, these depth limits have been expanded, as the water is hot and the visibility good.

 

[rivers]

rivers, you're right; my memory had failed me. Thanks for the correction.

CMAS and BSAC had a falling-out and went their separate ways in the late 90s.

But BSAC was part of CMAS way back in the mid-90s when my buddy got trained and certified in accordance with what were then CMAS standards … standards which allowed "sport divers" to do limited stage decompression diving.

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No problem.
And sports divers can still do deco (and even take ADP to accelerate it). No clue if it's limited though. I know personally, I have done what's amounted to about 25 minutes deco with all stops (15, 12, 9, 6, and 1 metre/min from 6 to the surface), and i'm technically only a sports diver in the eyes of BSAC.

 

[DuboisP]

Just think about the gas requirements if things go wrong... you don't want to go into deco with one cylinder.

things go rarely wrong, if you plan carefully your consumption with some security, have good and redundant hardware.
even when diving one cylinder, i always use 2 separated regulators, have 2 smb.
i never was out of gas, even after a decompression time of 10 or 15 minutes, never has a regulator or hose failure.

 

[alewar]

things go rarely wrong, if you plan carefully your consumption with some security, have good and redundant hardware.
even when diving one cylinder, i always use 2 separated regulators, have 2 smb.
i never was out of gas, even after a decompression time of 10 or 15 minutes, never has a regulator or hose failure.

It can happen that your buddy runs out of air and panics. You have to have enough air for the safe ascend of two divers with high SACs... that doesn't leave you much for the bottom time.

 

[DuboisP]

It can happen that your buddy runs out of air and panics. You have to have enough air for the safe ascend of two divers with high SACs... that doesn't leave you much for the bottom time.

nope.
if i'm the supervisor, my buddy won't be out of air, that's my responsability, and we won't go deeper than 20m or 40m, depending his level, so probably, without decompression, or just a few.
if we're at the same level, we won't be out of gas, and we won't panic.
if we plan some problem, we won't dive, or we will dive without decompression..

plan your dive, dive your plan.

 

[Edward3c]

No problem.
And sports divers can still do deco (and even take ADP to accelerate it). No clue if it's limited though. I know personally, I have done what's amounted to about 25 minutes deco with all stops (15, 12, 9, 6, and 1 metre/min from 6 to the surface), and i'm technically only a sports diver in the eyes of BSAC.

Your a diver qualified to dive to the limites of whatever qualification you hold, your not a BSAC Sports Diver unless your do, and pass, the course.

A BSAC Sports Diver can:
* with appropriate training, dive to 80m on Trimix - or even go down the Rebreather route to the same depth.
* take the Instructor Foundation Course.

The limit of any deco for a SD is the gas(es) that can be carried following a detailed run-time plan, including bailout gas for the buddy.

 

[rivers]

Your a diver qualified to dive to the limites of whatever qualification you hold, your not a BSAC Sports Diver unless your do, and pass, the course.

A BSAC Sports Diver can:
* with appropriate training, dive to 80m on Trimix - or even go down the Rebreather route to the same depth.
* take the Instructor Foundation Course.

The limit of any deco for a SD is the gas(es) that can be carried following a detailed run-time plan, including bailout gas for the buddy.

Ehh, my sports diver course was just me go diving and ticking off boxes, such as "oh look, you put your blob up that dive" or "oh hey, you ran some line" or "hey, I'll throw a random OOA at you mid dive and see what you do". I already had a decent amount of UK experience when I joined my BSAC club, and it was just really ticking the boxes so I had a qualification BSAC would recognise (since BSAC at the national level seem to have a problem with GUE [club level couldn't care]). Even then, it took me over a year to send off for the card, and that was only so I could technically enroll in ADP.

 

[Edward3c]

Ehh, my sports diver course was just me go diving and ticking off boxes, such as "oh look, you put your blob up that dive" or "oh hey, you ran some line" or "hey, I'll throw a random OOA at you mid dive and see what you do". I already had a decent amount of UK experience when I joined my BSAC club, and it was just really ticking the boxes so I had a qualification BSAC would recognise (since BSAC at the national level seem to have a problem with GUE [club level couldn't care]). Even then, it took me over a year to send off for the card, and that was only so I could technically enroll in ADP.

From what your saying you didn't actually do the Sports Diver course. In fact you didn't even complete the distance line and DSMB lessons or undertake the required Alternate Supply or full blown OOG assessments. Sounds like a deviation from BSAC standards.

I was under the impression GUE did all the 'technical' skills you would be looking for in BSAC's ADP course, so why switch agency. You can dive (but not train) within BSAC with your current GUE qualifications, however, the legal requirement to ensure your buddy knows what to do in the event of an OOG situation - is yours.

 

[doctormike]

nope.
if i'm the supervisor, my buddy won't be out of air, that's my responsability, and we won't go deeper than 20m or 40m, depending his level, so probably, without decompression, or just a few.
if we're at the same level, we won't be out of gas, and we won't panic.
if we plan some problem, we won't dive, or we will dive without decompression..

plan your dive, dive your plan.

I guess things are different with other agencies, and other country's dive cultures. This post has a number of statements that are not in keeping with technical diving training as I understand it. Don't want to get into a flame war, but as others have pointed out, I don't think that the difference between recreational and technical diving is simply a quantitative difference but a qualitative difference with a different mindset.

Assuming that the "supervisor" (does this mean instructor or more advanced buddy?) will be monitoring the other diver's gas - as opposed to planning that all ahead of time and for each diver being responsible for monitoring their own gas supply - is dangerous even for a no-stop dive, let alone a dive that requires staged decompression.

With "just a few" [minutes] of decompression, what happens when the newer diver has a problem at depth and the instructor is not available? Since there is no option to ascend immediately, are they practiced at holding stops, and have those required stops somewhere written down?

If you are at the same level but one of you has a catastrophic gas loss due to an equipment failure, what's the plan then? With buddy? Without?