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aerobrain
27-09-2013, 04:18 PM
Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds)

My manual is at home and we will soon be on the beer so need to solve before we get handbags out :-)

kingfisher
27-09-2013, 06:54 PM
Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds)

My manual is at home and we will soon be on the beer so need to solve before we get handbags out :-)

If you are diving as a pair, it is double.

Enough for you to complete your own deco requirements using your deco gas and enough for you to also give your deco gas to your buddy so he can complete the same deco requirements - i.e you both complete the deco times on the required gas (plus you will be using your back gas when your buddy is using your deco gas so you will both be adding conservatism.

gobfish1
27-09-2013, 07:39 PM
I'm so happy I never bother with all this gas planning bollox

JPTaylor
28-09-2013, 07:23 AM
...

Mark Chase
28-09-2013, 08:36 AM
Buddy OC gas reserves on deco gas????

All fine and dandy till you get to 70m+ then it all goes to rat s#it

Its hard enough to carry your own gas needs

ATB

Mark

Dammyla
28-09-2013, 11:44 AM
To be fair mark, by the time you are doing 70+M, you should know enough to make your own mind up

I was taught to go with x2 at the andp level but as most of the people I dive with are same ocean, same shot line buddies, I worry about myself first and them later

I stick to x2 ish for proper buddy diving

The Duck
28-09-2013, 08:38 PM
Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds) ...

At the risk of actually answering the question ;) ...

My TDI Deco Procs book (2000) does not contain [any] recommendations for reserve gas.

In fact the only reconmendation for deco gas reserves is in "Extended Range Diving & Trimix" (2002), which is x1.5, thought this reads more of a recommendation and not a hard & fast rule.

In my old worked examples 1.5 was used.

iamyourgasman
29-09-2013, 10:33 AM
On my ANDP and Trimix course we used 1.5x for deco gas planning.

Woz
29-09-2013, 05:27 PM
Easier to work out the max deco you can do on the deco cylinder you own then plan dives that need less than this. Tada! One gas calc does all your planning forever. Well until you go diving stupidly deep with Chasey.

Mark Chase
29-09-2013, 06:00 PM
I am assuming all these people who carry deco gas reserves for their buddy have deco stages with two regs on, preferably one a longer reg?

In the real world, you can easily loose back gas but itís pretty hard to loose deco gas. That said there have been incidence such as Captain Deco who switched to his 50% to find it was 50% oil and un-breathable.

In such circumstances I have herd and\ read it said you should deco out on back gas????? What utter rubbish.

The safest course of action is to plan deco normally and then plan deco on a single gas option. IE if your carrying 32% and 80% you should be able to finish deco on either gas. The operational window for this strategy is very small. (do the deco numbers on 32% and you will see why) but it is a stop gap option from that to a drop tank

The most sensible course of action always being a drop tank and yellow bag protocol.


ATB

Mark

Janos
29-09-2013, 06:21 PM
Remember that TDI Deco Procedures is a single deco gas course.

I don't know what the TDI answer is, but when I was doing 40m dives with a cylinder of 50%, I found it helpful to plan through failures. So I would work out what would happen if I had a catestrophic failure at the end of my dive, then spent an extra 5 minutes sorting it out and putting up a blob / returning to the shot. How much backgas would I need? What would my new deco stops requirement be? How much 50% would I need to do that, etc etc.

I planned through a few scenarios, including a lost 50% scenario, and that told me the time and gas pressure I'd start my ascent on - whichever came first.

Do that for 40m, 35m, and 30m, and remember those numbers (and write a slate with the deco times on) and the job's a good-un for whatever dive that comes up.

Janos

Chris Brown
29-09-2013, 06:55 PM
Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds)

My manual is at home and we will soon be on the beer so need to solve before we get handbags out :-)

Here is a link to the standards. You will see that there is no set requirement as protocol may vary in different areas based on local environments. In Florida I taught 1.2, however at this level, with an Al40 and say 15 - 20 minutes of deco, you will have roughly double anyway. I will likely change it to 1.5 for the UK.

TDI Advanced Nitrox | Decompression Procedures Course Standards (http://www.chrisbrowntechnical.co.uk/tdi-advanced-nitrox-|-decompression-procedures-course-standards)

Have a debate with your buddies and come up with a number based on experience, RMV and the support you have available on a dive.

Iain Smith
29-09-2013, 07:53 PM
I am assuming all these people who carry deco gas reserves for their buddy have deco stages with two regs on, preferably one a longer reg?

No. But our "lost gas" plan doesn't rely on both divers breathing the deco gas at the same time. (FWIW, it's add 50% to the stop times and alternate who breaths the deco gas at each stop).


In the real world, you can easily loose back gas but itís pretty hard to loose deco gas. That said there have been incidence such as Captain Deco who switched to his 50% to find it was 50% oil and un-breathable.

In such circumstances I have herd and\ read it said you should deco out on back gas????? What utter rubbish.

Why? It's a perfectly legitimate strategy, albeit one I would hope to avoid. Remember that we're talking about single deco gas dives here. If you have an unbreathable deco gas you have two options. Deco out on back gas or deco out on your buddy's spare deco gas using whatever plan the pair of you agreed before the dive.


The safest course of action is to plan deco normally and then plan deco on a single gas option. IE if your carrying 32% and 80% you should be able to finish deco on either gas. The operational window for this strategy is very small. (do the deco numbers on 32% and you will see why) but it is a stop gap option from that to a drop tank

If you're talking about 32% backgas and 80% deco gas, then surely that contradicts your suggestion that back-gas deco is "utter rubbish", does it not? If you're talking about two deco gases, then that's not the sort of dive that the OP was asking about.


The most sensible course of action always being a drop tank and yellow bag protocol.

IMO, that's completely OTT for a single deco gas dive. You should be able to get out on your team's spare deco gas or (if you've all had contaminated fills) your backgas. If you're running two deco gases, you should be able to get out on either of your deco gases alone or (as above) share with your team.

Out of interest (and at risk of taking the conversation OT), how do you guarantee getting the drop-bottle to the diver? We had very little success when we experimented with one a decade or so ago, then gave it up as we concluded it wasn't needed (at least within the one or two deco gas range)

Iain

Paulo
29-09-2013, 08:15 PM
then that's not the sort of dive that the OP was asking about.


Welcome to TDF Iain, you must be new here?

MikeF
29-09-2013, 08:34 PM
Out of interest (and at risk of taking the conversation OT), how do you guarantee getting the drop-bottle to the diver? We had very little success when we experimented with one a decade or so ago, then gave it up as we concluded it wasn't needed (at least within the one or two deco gas range)

Iain

I always found that in a rib we'd clip the drop bottle to the smb line and slowly lower it down to the diver, off a hard boat we'd either lob it in somewhere close if the vis was good or get someone on the ladder* to clip it to the smb.

* for woz's benefit a ladder is a bit like a lift but you nimbly walk up it in little tiny steps instead of using a lift to haul you onboard like a harpooned whale being lifted onto a factory ship, ready to be rendered down for blubber.

notdeadyet
29-09-2013, 10:03 PM
I saw Simon TW trying out a system using a hulahoop which seemed to work well. You hoopla the SMB and it guides the bottle down. Seemed to work ok when he tried it out.

Personally, I dont tend to plan for a drop bottle.

Anyway, back to the OP. Decoing on backgas for a single gas switch dive doesn't strike me as unreasonable. I used to dive that way on OC. On air it gets unwieldy quick, on nitrox back gas it is a lot more manageable.

I also tend not to plan any reserves. I like to work backwards, I work out what my time limit is for the gas I've got and dive within it. My "reserve" becomes spare time.

Sent from my GT-I9100 using Tapatalk 2

Mark Chase
30-09-2013, 05:36 AM
Remember that TDI Deco Procedures is a single deco gas course.

I don't know what the TDI answer is, but when I was doing 40m dives with a cylinder of 50%, I found it helpful to plan through failures. So I would work out what would happen if I had a catestrophic failure at the end of my dive, then spent an extra 5 minutes sorting it out and putting up a blob / returning to the shot. How much backgas would I need? What would my new deco stops requirement be? How much 50% would I need to do that, etc etc.

I planned through a few scenarios, including a lost 50% scenario, and that told me the time and gas pressure I'd start my ascent on - whichever came first.

Do that for 40m, 35m, and 30m, and remember those numbers (and write a slate with the deco times on) and the job's a good-un for whatever dive that comes up.

Janos



When I did it we did two gas and three deco gas procedures??


ATB

Mark

Mark Chase
30-09-2013, 05:48 AM
No. But our "lost gas" plan doesn't rely on both divers breathing the deco gas at the same time. (FWIW, it's add 50% to the stop times and alternate who breaths the deco gas at each stop).



Why? It's a perfectly legitimate strategy, albeit one I would hope to avoid. Remember that we're talking about single deco gas dives here. If you have an unbreathable deco gas you have two options. Deco out on back gas or deco out on your buddy's spare deco gas using whatever plan the pair of you agreed before the dive.



If you're talking about 32% backgas and 80% deco gas, then surely that contradicts your suggestion that back-gas deco is "utter rubbish", does it not? If you're talking about two deco gases, then that's not the sort of dive that the OP was asking about.



IMO, that's completely OTT for a single deco gas dive. You should be able to get out on your team's spare deco gas or (if you've all had contaminated fills) your backgas. If you're running two deco gases, you should be able to get out on either of your deco gases alone or (as above) share with your team.

Out of interest (and at risk of taking the conversation OT), how do you guarantee getting the drop-bottle to the diver? We had very little success when we experimented with one a decade or so ago, then gave it up as we concluded it wasn't needed (at least within the one or two deco gas range)

Iain




Iain this is TDI Advanced Nitrox & Decompresion Procedures

We dont have a single gas limit, we dont have a bottom time limit and we dont have a deco limit.

Your putting GUE Tec1 limits on a TDI course????

The operational window for a back gas deco option is miniscule. It reely only works up to 40-45m or very very short bottom times (like 20mins) at 45-55m


I am talking about 21% back gas and 32 & 80 for deco. or 50 &100 for deco. doesnt reely matter just so long as you have two deco gas.

ATB

Mark

Mark Chase
30-09-2013, 05:55 AM
Out of interest (and at risk of taking the conversation OT), how do you guarantee getting the drop-bottle to the diver? We had very little success when we experimented with one a decade or so ago, then gave it up as we concluded it wasn't needed (at least within the one or two deco gas range)

Iain


Done it twice in anger, once on loyal watcher and once on Defiant. No problems on either boat. Done it practicing on Steve Johnsons boat. No problem to report.


Safest way?

Send up yellow SMB

Boat collects Yellow SMB and clips deco tank to SMB line

Deco gas lands on your reel.


Loyal watcher use the hoola hoop system or on slack water good viz the chuck it in next to the diver system. I dont like this but aparently and demonstrably, it does work.

ATB

Mark

Iain Smith
30-09-2013, 07:41 AM
Iain this is TDI Advanced Nitrox & Decompresion Procedures

Yep.


We dont have a single gas limit, we dont have a bottom time limit and we dont have a deco limit.

Your putting GUE Tec1 limits on a TDI course????[/quote]

Not intentionally. Like Janos, my TDI Decompression Procedures course was single deco gas only. I guess the multiple deco gases version is a hang-over from deep air, as I can't imagine why you would need more than one deco gas for a nitrox dive.


The operational window for a back gas deco option is miniscule. It reely only works up to 40-45m or very very short bottom times (like 20mins) at 45-55m

Depends where you're coming from. For many divers with nothing more than a basic nitrox ticket, 20min @ 55m would be a huge step up. Then again, it goes without saying that ANX/DP is not the course I would promote for that sort of dive...

Iain

Chris Thomas
30-09-2013, 08:02 AM
Depends where you're coming from. For many divers with nothing more than a basic nitrox ticket, 20min @ 55m would be a huge step up. Then again, it goes without saying that ANX/DP is not the course I would promote for that sort of dive...

Iain

ANX/DP is a 45m course, Extended Range is the 55m air ticket with TDI. Most sensible people would now choose the TDI Normoxic Trimix, which is 60m.

My ANX/DP was single deco gas and I was told two stages was ER/Tx.

The numbers don't add up carrying two deco gases in the 45m region, unless you want a mix you can get on deep.

30 mins @ 45m, 35/85GF, Air

Air deco - 83mins stops
50% - 40 mins
70% - 35 mins
32/80 - 34 mins

steve6690
30-09-2013, 08:14 AM
ANX/DP is a 45m course, Extended Range is the 55m air ticket with TDI. Most sensible people would now choose the TDI Normoxic Trimix, which is 60m.

My ANX/DP was single deco gas and I was told two stages was ER/Tx.

The numbers don't add up carrying two deco gases in the 45m region, unless you want a mix you can get on deep.

30 mins @ 45m, 35/85GF, Air

Air deco - 83mins stops
50% - 40 mins
70% - 35 mins
32/80 - 34 mins



Sent from my GT-I9300 using Tapatalk 2

The case for using two deco gases is stronger if you want to increase bottom time.

Chris Thomas
30-09-2013, 08:32 AM
So 45mins at 45m

Air deco - 176 mins stops
70% - 64 mins
32/80% - 60 mins
50/100% - 50 mins

Ok, so I can't get out on back gas alone, but I'd still rather carry one stage and have a drop bottle on the boat for this dive.

Woz
30-09-2013, 08:39 AM
I always found that in a rib we'd clip the drop bottle to the smb line and slowly lower it down to the diver, off a hard boat we'd either lob it in somewhere close if the vis was good or get someone on the ladder* to clip it to the smb.

* for woz's benefit a ladder is a bit like a lift but you nimbly walk up it in little tiny steps instead of using a lift to haul you onboard like a harpooned whale being lifted onto a factory ship, ready to be rendered down for blubber.

I have scampered up many a ladder. The last one to climb up onto your mum.

steve6690
30-09-2013, 09:12 AM
So 45mins at 45m

Air deco - 176 mins stops
70% - 64 mins
32/80% - 60 mins
50/100% - 50 mins

Ok, so I can't get out on back gas alone, but I'd still rather carry one stage and have a drop bottle on the boat for this dive.

On a typical day boat I probably wouldn't trust that the bottle would get to me. I'd rather carry it.

edward
30-09-2013, 09:25 AM
On a typical day boat I probably wouldn't trust that the bottle would get to me. I'd rather carry it.

I too would take two bottles into that particular shower - and I make sure I could get out on just one of the two deco bottles in case one goes pop. Your probably not going to get out on backgas at that kind of bottom time. I dive solo a fair bit which I guess colours my view on this. And I have a normoxic ticket and two stages feels normal to me. YMMV

notdeadyet
30-09-2013, 10:10 AM
So 45mins at 45m

Air deco - 176 mins stops
70% - 64 mins
32/80% - 60 mins
50/100% - 50 mins

Ok, so I can't get out on back gas alone, but I'd still rather carry one stage and have a drop bottle on the boat for this dive.

Dives like that I still only take one deco bottle. Yep, backgas isn't enough and yep, the deco bottle may fail unrecoverably but I'm happy the chances of it happening are so remote.

Risk is as much about probability as it is about the event.

Mark Chase
30-09-2013, 01:57 PM
Yep.



Your putting GUE Tec1 limits on a TDI course????

Not intentionally. Like Janos, my TDI Decompression Procedures course was single deco gas only. I guess the multiple deco gases version is a hang-over from deep air, as I can't imagine why you would need more than one deco gas for a nitrox dive.



Depends where you're coming from. For many divers with nothing more than a basic nitrox ticket, 20min @ 55m would be a huge step up. Then again, it goes without saying that ANX/DP is not the course I would promote for that sort of dive...

Iain[/QUOTE]


No problem. I can see nitrox back gas single deco working but not many doing that sort of diving thease days

My deco cert covered me all the way up to CCR. If you have deco procedures you dont need to do Mod2 CCR as your already deco qualified.

Theres no such thing as advanced deco procedures.

In truth the Deco Procedures manual i have (2000) doesent mention any limit on haw many deco gas you use nor does it mention multiple tanks specificly. It just sais things like when using multiple stages you may need a bigger lift capacity BCD???

As I said before, my instructor taught two deco stages and went on to discuss handling a third which was normaly used as a travel gas. We didnt do any training on the third tank. All the drills were on two gas deco.


ATB

Mark

Chris Brown
30-09-2013, 04:11 PM
Some interesting interpretations of the TDI courses in this thread.

Just to clarify, there are no official courses called 'Mod1" and "mod2" although people love to call them that.

Theres Advanced Nitrox, Helitrox and Decompression Procedures and CCR Air Diluent Diver and CCR Air Diluent Diver Decompression Procedures and then CCR Mixed Gas diluent.

These are the courses that are relevant to the discussion on this thread so far.

You need to have either advanced nitrox & deco procedures to enter a CCR Air Dil Deco course, or the basic CCR Air Dil Diver qualification. Once you have done that and have 50 hours experience over 50 dives, you can enrol on a CCR mixed gas diluent course (AKA Mod 2)

Mark Chase
30-09-2013, 05:06 PM
Some interesting interpretations of the TDI courses in this thread.

Just to clarify, there are no official courses called 'Mod1" and "mod2" although people love to call them that.

Theres Advanced Nitrox, Helitrox and Decompression Procedures and CCR Air Diluent Diver and CCR Air Diluent Diver Decompression Procedures and then CCR Mixed Gas diluent.

These are the courses that are relevant to the discussion on this thread so far.

You need to have either advanced nitrox & deco procedures to enter a CCR Air Dil Deco course, or the basic CCR Air Dil Diver qualification. Once you have done that and have 50 hours experience over 50 dives, you can enrol on a CCR mixed gas diluent course (AKA Mod 2)

Sure but Chris we always refer to them as Mod1 Mod2 and Mod3


And are you sure about the second bit? I understood you only needed a Nitrox cert to do Mod 1 Air Dill no Deco?

If you didnt have Decompresion procedures you needed Mod2 (I never did Mod2 not have i ever done a deco course on CCR) Air Dill + Deco

If you had decompresion procedures and 50 hours or Mod 2 + 50 hours (lucky buggeres it was 100 when i took it) you could do CCR trimix which we called Mod3

ATB

Mark

Chris Brown
30-09-2013, 05:46 PM
Sure but Chris we always refer to them as Mod1 Mod2 and Mod3


And are you sure about the second bit? I understood you only needed a Nitrox cert to do Mod 1 Air Dill no Deco?

If you didnt have Decompresion procedures you needed Mod2 (I never did Mod2 not have i ever done a deco course on CCR) Air Dill + Deco

If you had decompresion procedures and 50 hours or Mod 2 + 50 hours (lucky buggeres it was 100 when i took it) you could do CCR trimix which we called Mod3

ATB

Mark

Yes, and you are kind of right. I guess it doesnt matter what they were called as there are new courses.

Ill list the certs and prerequisites, should make it clearer when referencing old levels to new courses:

Advanced Nitrox- 40m with EANX21 - 100. NO deco - Prerequisites - Nitrox and 25 dives

Decompression Procedures - 45m on AIR. Can be combined with Advanced Nitrox, Advanced Wreck or Extended Range - Prerequisites - Nitrox and 25 dives

CCR Air Dil Unit Specific Course - 30m on AIR. NO deco. - Prerequisites - Nitrox and 20 dives

CCR Air Dil Decompression Procedures Unit Specific Course - 45m on AIR with deco. - Prerequisites - Advanced Nitrox and Deco Procedures diver OR CCR Air Dil Diver + 30 Hours + 6 months experience

CCR Mixed Gas Dil Unit Specific Course - 60m with 16% or greater f02. Prerequisites - 50 hours over 50 dives, of which half must have been deeper than 20m, all deeper than 9m. Must also have completed CCR Air Dil Decompression Procedures or equivalent.

For those wondering about "mod3" / Advanced Trimix CCR:

Advanced Mix Gas CCR Diver Unit Specific Course - 100m any mix. prerequisites - CCR Air Dil Deco Diver, 100 hours over 100 dives on the specific unit, of which half must be deeper than 30m

Mark Chase
30-09-2013, 09:42 PM
Yes, and you are kind of right. I guess it doesnt matter what they were called as there are new courses.

Ill list the certs and prerequisites, should make it clearer when referencing old levels to new courses:

Advanced Nitrox- 40m with EANX21 - 100. NO deco - Prerequisites - Nitrox and 25 dives

Decompression Procedures - 45m on AIR. Can be combined with Advanced Nitrox, Advanced Wreck or Extended Range - Prerequisites - Nitrox and 25 dives

CCR Air Dil Unit Specific Course - 30m on AIR. NO deco. - Prerequisites - Nitrox and 20 dives

CCR Air Dil Decompression Procedures Unit Specific Course - 45m on AIR with deco. - Prerequisites - Advanced Nitrox and Deco Procedures diver OR CCR Air Dil Diver + 30 Hours + 6 months experience

CCR Mixed Gas Dil Unit Specific Course - 60m with 16% or greater f02. Prerequisites - 50 hours over 50 dives, of which half must have been deeper than 20m, all deeper than 9m. Must also have completed CCR Air Dil Decompression Procedures or equivalent.

For those wondering about "mod3" / Advanced Trimix CCR:

Advanced Mix Gas CCR Diver Unit Specific Course - 100m any mix. prerequisites - CCR Air Dil Deco Diver, 100 hours over 100 dives on the specific unit, of which half must be deeper than 30m




That is confusing as hell???

So you need to be OC decompresion qualified BEFORE you can do CCR decompresion??


I thaught it ment if you already had OC decompresion Procedures you didnt need to do the course at all?

If not my certs a bit of a joke as I never did CCR deco procedures before I did my 100m mix cert.

I beleive i am right in saying, back when i did my TDI CCR trimix, the instructor had the power to say if hed grant a 60m or 100m cert bassed on diver performance.

ATB

Mark

JPTaylor
01-10-2013, 06:18 AM
If not my certs a bit of a joke as I never did CCR deco procedures before I did my 100m mix cert.

Sorry Mark but your certs are obviously invalid and I think you should talk to Chris about doing a retake! :D




Sent from my iPad using Tapatalk - now Free (http://tapatalk.com/m?id=1)

Chris Brown
01-10-2013, 07:36 AM
That is confusing as hell???

So you need to be OC decompresion qualified BEFORE you can do CCR decompresion??


I thaught it ment if you already had OC decompresion Procedures you didnt need to do the course at all?

If not my certs a bit of a joke as I never did CCR deco procedures before I did my 100m mix cert.

I beleive i am right in saying, back when i did my TDI CCR trimix, the instructor had the power to say if hed grant a 60m or 100m cert bassed on diver performance.

ATB

Mark

I dont think its confusing to those who werent exposed to the old Mod1, Mod2, Mod3, but I can see where you are coming from.

The first course you do on a CCR is about the unit. How to dive it, maintain it and how it works and what to do in an emergency. Theres simply no time or bandwidth to teach people decompression diving at the same time. So, if they have no prior Deco training, then they do CCR Air Dil Diver. If they DO have prior deco training, then they can start at CCR air dil decompression procedures diver. OR, if they have already done CCR Air Dil Diver and have at least 30 hours experience over 6 months they can start with CCR Air Dil Deco Procedures diver.

Im assuming you had OC trimix before you did your CCR training? Plus the old MOD1 included deco IIRC (I was mainly teaching IANTD then and cant remember). That might be the reason for your training path.

Mark Chase
01-10-2013, 07:42 AM
I dont think its confusing to those who werent exposed to the old Mod1, Mod2, Mod3, but I can see where you are coming from.

The first course you do on a CCR is about the unit. How to dive it, maintain it and how it works and what to do in an emergency. Theres simply no time or bandwidth to teach people decompression diving at the same time. So, if they have no prior Deco training, then they do CCR Air Dil Diver. If they DO have prior deco training, then they can start at CCR air dil decompression procedures diver. OR, if they have already done CCR Air Dil Diver and have at least 30 hours experience over 6 months they can start with CCR Air Dil Deco Procedures diver.

Im assuming you had OC trimix before you did your CCR training? Plus the old MOD1 included deco IIRC (I was mainly teaching IANTD then and cant remember). That might be the reason for your training path.



Edited due to a miss read of Chris's post.



ATB

Mark

iamyourgasman
01-10-2013, 08:04 AM
Mark, according to Chris, nothing ;). As I understand if you are OC deco/trimix trained you can get an air diluent deco ticket on your first user course if you go with TDI. Quite why is it air diluent only is another question!

Mark Chase
01-10-2013, 08:08 AM
Mark, according to Chris, nothing ;). As I understand if you are OC deco/trimix trained you can get an air diluent deco ticket on your first user course if you go with TDI. Quite why is it air diluent only is another question!

Your quite right, i miss read it sorry Chris


ATB

Mark

Foggy
01-10-2013, 08:15 AM
Your quite right, i miss read it

"Ach mein gott, I said subtle retreat, NOT scuttle the fleet!" ;)



sorry Chris
Reported to the forum police.....violation of unwritten rule re: un-demanded apologies :):)

Chris Thomas
01-10-2013, 08:17 AM
Yeah, really, if you have deco procedures and advanced nitrox, you should really do 'Mod 1' on trimix to 45m.

21/35 doesn't significantly change deco requirements, I don't see why it's not included in all Mod 1's.

JPTaylor
01-10-2013, 08:23 AM
21/35 doesn't significantly change deco requirements, I don't see why it's not included in all Mod 1's.

Because then you couldn't be charged for another course!!

Chris Thomas
01-10-2013, 08:27 AM
Too true!

Mark Chase
01-10-2013, 08:37 AM
Yeah, really, if you have deco procedures and advanced nitrox, you should really do 'Mod 1' on trimix to 45m.

21/35 doesn't significantly change deco requirements, I don't see why it's not included in all Mod 1's.


Totaly agree. Forcing divers to do a load of 30m+ diving prior to being allowed mix is just insain in UK conditions.

I dive trimix from Day 1 after the Mod1 course.

ATB

Mark

steve6690
01-10-2013, 09:06 AM
Totaly agree. Forcing divers to do a load of 30m+ diving prior to being allowed mix is just insain in UK conditions.

I dive trimix from Day 1 after the Mod1 course.

ATB

Mark

I agree. I think a new thread is in order. Stand by. ..

Sent from my GT-I9300 using Tapatalk 2

Chris Thomas
01-10-2013, 09:15 AM
I agree. I think a new thread is in order. Stand by. ..

Sent from my GT-I9300 using Tapatalk 2

What's wrong with this thread? It's TDF, it doesn't have to be on topic.

I'll be diving helium where I can when I do a Mod 1. I'll not be below my certified depth until I have the experience, but I will be building my experience up with a clear head.

Chris Thomas
01-10-2013, 09:15 AM
What's wrong with this thread? It's TDF, it doesn't have to be on topic.

I'll be diving trimix where I can when I do a Mod 1. I'll not be below my certified depth until I have the experience, but I will be building my experience up with a clear head.

JPTaylor
01-10-2013, 09:28 AM
I'll be diving helium where I can when I do a Mod 1. I'll not be below my certified depth until I have the experience, but I will be building my experience up with a clear head.

One issue is buoyancy control, rapid uncontrolled ascents are maybe better done on Air rather than Helium mixes?

I did about 20hrs before I used a weak mix (16/24), I'd sorted out my weight (dropped a lot of lead post course) & practiced simulated deco stop dives making sure I could easily hold 12/9/6m stops and also stop/hold a 3m stop in the sea.

I went down the HeliAir route, using 16/24, 15/29 (still a favorite), 12/42 & 10/52 before I got around to doing a Mod 2 (PSAI 70m ticket)

Chris Thomas
01-10-2013, 09:38 AM
Totally agree with that approach. I'm not looking to push my luck and will be taking it steady until I'm comfortable with the unit and my buoyancy.

JPTaylor
01-10-2013, 11:21 AM
Totally agree with that approach. I'm not looking to push my luck and will be taking it steady until I'm comfortable with the unit and my buoyancy.

I still find 30-35m 'ish dives with just a brief deco stop at 6m, trickier than deeper dives where first stop maybe 21m or deeper.

Why? Temptation is to come barreling up to 6m with set-point & loop volume all over the place, then buoyancy at 6m goes to rat shit! On deeper dives you sort this stuff out by default on deeper stops.

Still practice what I was told on my Mod 1, always stop at 12m even if deco stop shallower, to sort out loop volume & let SP stabilize before ascending to 9/6m stops.

Big Matt
01-10-2013, 11:49 AM
at the risk of opening a can of worms i have a question. actually it's more like a request for advice really.

currently BSAC DL/OWI, with ADP, and want to move onto trimix to allow progression onto some deeper stuff i.e 40-50m. not interested in going any deeper than that. i'm after a course that will teach this but also certify me for primary donate so i can fulfill my duty of care with BSAC. have been taught it but no formal certification. don't want to start a debate about the hog looping thing all over again, it is what it is, just after peoples opinions on TDI, IANTD etc. and which course might be best suit my needs.

opinions? :think:

Mark Powell
01-10-2013, 11:56 AM
Yeah, really, if you have deco procedures and advanced nitrox, you should really do 'Mod 1' on trimix to 45m.

21/35 doesn't significantly change deco requirements, I don't see why it's not included in all Mod 1's.

Are you suggesting something like Helitrox on Mod 1?

Chris Thomas
01-10-2013, 12:12 PM
Are you suggesting something like Helitrox on Mod 1?

Yeah, makes sense.

Given a choice, most people would dive trimix on dives deeper than 30m but the cost is prohibitive. The gas usage on CCR makes the cost of a trimix fill almost too cheap not to dive trimix beyond 30m.

Mark Powell
01-10-2013, 03:00 PM
Yeah, makes sense.

Given a choice, most people would dive trimix on dives deeper than 30m but the cost is prohibitive. The gas usage on CCR makes the cost of a trimix fill almost too cheap not to dive trimix beyond 30m.
OK, you have convinced me. It will be in the next issue of the TDI standards.

iamyourgasman
01-10-2013, 03:38 PM
OK, you have convinced me. It will be in the next issue of the TDI standards.

I think this would be a very forward thinking and reasonable stance from TDI UK. Having experienced quite a bit of warm water diving this year, I can see why it is air dil in those places (He is sometimes difficult to source and blend) but a choice of 21/35 over air dil for any depth on a rebreather for a UK or other cold water diver would be obvious. This is particularly true if they are already OC Trimix/helitrox trained.

gobfish1
01-10-2013, 10:30 PM
fook me you guys want it all ,

you post about guys taking mod 1 that are not up to the mark , diving with air then you say, hay ill sort them out with some He and a mod1 course , brill


if a diver has a breather and is only using air in said unit , then he needs a course for being a half wit . not a course about Helitrox what ever the fook that is lol


just to let some of you know , you can put what ever you like gas wise in your unit no one will mind ,

SonicStomp
01-10-2013, 10:43 PM
at the risk of opening a can of worms i have a question. actually it's more like a request for advice really.

currently BSAC DL/OWI, with ADP, and want to move onto trimix to allow progression onto some deeper stuff i.e 40-50m. not interested in going any deeper than that. i'm after a course that will teach this but also certify me for primary donate so i can fulfill my duty of care with BSAC. have been taught it but no formal certification. don't want to start a debate about the hog looping thing all over again, it is what it is, just after peoples opinions on TDI, IANTD etc. and which course might be best suit my needs.

opinions? :think:

I have a similar background. I did ADP and then did TDI Adv Nx & Deco procedures. I then decided after the TDI course that air diving below 40m sucked. I passed the course OK but did not enjoy the narcosis below 40m.

Subsequently I have done fundies and want to do T1 next. Although it would be two courses rather than one it would satisfy your desire to do trimix and learn primary donate. I believe there to be other benefits too :-)


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Mark Chase
02-10-2013, 05:05 AM
fook me you guys want it all ,

you post about guys taking mod 1 that are not up to the mark , diving with air then you say, hay ill sort them out with some He and a mod1 course , brill


if a diver has a breather and is only using air in said unit , then he needs a course for being a half wit . not a course about Helitrox what ever the fook that is lol


just to let some of you know , you can put what ever you like gas wise in your unit no one will mind ,



I totaly agree in principle but some people have wives kids and life insurance policies that wont pay out on divers diving outside their qualification.

I am very lucky my life dosetn work like that but if I were a 9-5er with a life insured mortguage id be a lot more conservitive about such things.

ATB

Mark

Major Clanger
02-10-2013, 05:37 AM
OK, you have convinced me. It will be in the next issue of the TDI standards.

Hallelujah. Been saying this is needed for years (18 months in reality). The right way forward. Furthermore TDI should recognise prior open circuit trimix qualifications when considering mod 1 training needs and certification.







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Mark Powell
02-10-2013, 07:55 AM
The right way forward. Furthermore TDI should recognise prior open circuit trimix qualifications when considering mod 1 training needs and certification.


Yep, if you are already Helitrox or Trimix qualifies then you will be able to use that within the limits of the Mod 1 certification. I have a copy of the standarda nd have been testing it out and it will be in the next issue of the standards which will be this quarter.

Big Matt
02-10-2013, 08:46 AM
I have a similar background. I did ADP and then did TDI Adv Nx & Deco procedures. I then decided after the TDI course that air diving below 40m sucked. I passed the course OK but did not enjoy the narcosis below 40m.

Subsequently I have done fundies and want to do T1 next. Although it would be two courses rather than one it would satisfy your desire to do trimix and learn primary donate. I believe there to be other benefits too :-)


Sent from my iPad using Tapatalk HD

my feelings exactly about deep air. just don't get on with it.