Trimix 1 Class [Archive]

cadet diver

March 4th, 2003, 11:25 PM

I am taking TDI Trimix 1 in 2 weeks in the Bahamas. I found out tonight from my instructor that some of the plans changed, and I am curious what other peoples beginner trimix classes were like. We are looking at profile of 200 for 15min on 21/35, and then just 50/50 for deco. Is this a pretty standard profile for the class or should I be expecting longer bottom times?

The other thing is that he said that he can't get al40s down there anymore, which he originally said that he could get. Therefore we are going to either have to bring our own bottles, or sling an al80. Has anyone ever done any deco in the Bahamas and had a similar problem before?

Thanks for any help you can provide.

Bottomfeeder

March 5th, 2003, 06:13 AM

cadet diver once bubbled...
We are looking at profile of 200 for 15min on 21/35, and then just 50/50 for deco. Is this a pretty standard profile for the class or should I be expecting longer bottom times?

15 minutes sounds about right for starting out, but the gas choice for that depth is too hot/high END.

chickdiver

March 5th, 2003, 08:12 AM

Cadet Diver-

The bottom time sounds about right, depending on the deco tables you are running, when I teach trmix (not TDI) I try and keep the run times (bottom time plus deco) int he 100 minute range. That gas mix is definitely hot. For example, running a dive to 190' I would teach (and use) 18/45. Also, generally when doing a one gas deco most people opt for O2 rather than 50/50. Decoing on an al80 isnt bad, but dragging it around during the dive will be less than comfortable (do NOT drop your deco gas, whatever the instructor does).

MechDiver

March 5th, 2003, 11:13 AM

IANTD limits normoxic trimix (assume same as Trimix 1) to 20/29 and either single 50/50 or dual 35% and 80%. I would have to disagree with ChickDiver over the use of 100%, at least here. 50% is much more common IME.

At least to IANTD guidelines, the 21/35 fits. We did 200 fsw on 20/30.

MD

chickdiver

March 5th, 2003, 11:53 AM

Mech-

Im not familiar with IANTD or TDI's standards or class structures. The difference re: 50/50 or O2 for a single deco gas may be regional? In Florida I have never seen anyone use 50/50 for a single deco gas dive.....

MikeFerrara

March 5th, 2003, 12:02 PM

The IANTD Normoxic trimix class requires the use of one deco gas. The deco gas can be anything up to 100% O2. For short bottom times there won't be much of a difference in the schedule between using 50/50 and O2 but I would rather have O2. The course also requires that no dive be more than 33 ft deeper than your deepest dive to date also 200 ft is the max depth allowed in the class.

IMO, short bottom times are ok for SOME of the training dives because skills like hitting runtimes, gas switches, shooting a bag ect) mostly come in during the ascent.

padiscubapro

March 5th, 2003, 12:20 PM

I have to agree with mech.. I would never use oxygen when only carrying a single deco gas.. 50/50 up in the northeast is much more common.. using 50/50 gives you more options.. better than carying a gas thats useless deeper than 20 fsw.. assuming a contingency po2 of 2.0 (must be ascending) you can bail onto 50/50 at 100 fsw if necessary.. If using a high helium bottom gas I would still use 50% oxygen but would add some helium to the gas.. I prefer not to raise the FN2 over the bottom gas when possible..
We used fixed ascent and descent lines, I plan all decos using 50/50 and calculate schedule as such, I will have o2 hanging beneath the boat on either a trapeze or on the ascent line.. The o2 is not a required decos gas so it doesn't have to be carried but if all goes well, I will switch to 100% at 20fsw, and still run my 50/50 schedule.
If I have to shoot a bag and deco away from the line I still have the necessary gas needed..

for bottom gas I would use 20/25 (130 END) or 20/35 (100 END) for a 200 fsw dive.. This keeps the END and deco times reasonable. If I remember correctly TDI allows o2 as low as 18% on its entry level trimix program.. There was no requirement prior to last year..

MHK

March 5th, 2003, 01:50 PM

cadet diver once bubbled...
I am taking TDI Trimix 1 in 2 weeks in the Bahamas. I found out tonight from my instructor that some of the plans changed, and I am curious what other peoples beginner trimix classes were like. We are looking at profile of 200 for 15min on 21/35, and then just 50/50 for deco. Is this a pretty standard profile for the class or should I be expecting longer bottom times?

The other thing is that he said that he can't get al40s down there anymore, which he originally said that he could get. Therefore we are going to either have to bring our own bottles, or sling an al80. Has anyone ever done any deco in the Bahamas and had a similar problem before?

Thanks for any help you can provide.

In my view, as others have experessed, the mix is hot but more importantly it seems to me that the focus is on the wrong thing. Depth and mix aren't the key things to focus on. You haven't really described the class in great detail so it's hard for me to comment, but from what I see, going to depth before any pre-dive evaluations and skill assesment seems short sighted to me. When we run our classes we do 4 dives in the 20' range before we even consider letting a diver go to depth.. Perhaps they will do this as well, but in my view skills are more important then depth and mix..

Hope that helps

O-ring

March 5th, 2003, 01:57 PM

cadet diver once bubbled...
I am taking TDI Trimix 1 in 2 weeks in the Bahamas. I found out tonight from my instructor that some of the plans changed, and I am curious what other peoples beginner trimix classes were like. We are looking at profile of 200 for 15min on 21/35, and then just 50/50 for deco. Is this a pretty standard profile for the class or should I be expecting longer bottom times?

The other thing is that he said that he can't get al40s down there anymore, which he originally said that he could get. Therefore we are going to either have to bring our own bottles, or sling an al80. Has anyone ever done any deco in the Bahamas and had a similar problem before?

Thanks for any help you can provide.
Is that your first dive for the class? In my class we are building up slowly to those kinds of depths (i.e. starting with the pool, then the quarry, then 130-140, then to 150-160, then to 190-200 for the final dives). All of our dives are using decoplanner and GUE standardized gas mixes...so for that dive we would probably run about the same bottom time as you, but would definitely knock that o2 back to 18 and the He up to 45.. That way, you can keep your ppo2 down to a nice 1.2-1.3 and your END under 100'.

cadet diver

March 5th, 2003, 01:58 PM

We will be doing 6 shallower skill dives in addition to the deeper dives, with 1 deep dive a day. My instructor was the same instructor I had for my Extended Air Nitrox class, so we have already done dives to those depths on air together. I know that doesnt go along with GUE standards because of deep air and the difference in the class progression.

cadet diver

March 5th, 2003, 02:01 PM

Sorry for the confusion. Not all of our dives are going to be to exactly 200. There will be several in the 150-170 range. I think you guys answered my questions though.

MechDiver

March 5th, 2003, 02:15 PM

MHK once bubbled...

In my view, as others have experessed, the mix is hot but more importantly it seems to me that the focus is on the wrong thing. Depth and mix aren't the key things to focus on. You haven't really described the class in great detail so it's hard for me to comment, but from what I see, going to depth before any pre-dive evaluations and skill assesment seems short sighted to me. When we run our classes we do 4 dives in the 20' range before we even consider letting a diver go to depth.. Perhaps they will do this as well, but in my view skills are more important then depth and mix..

Hope that helps

Why should he have described the class "in great detail"? He had a simple question related to the mix being used, not how many times he had to do handstands underwater. A *little* break from the party line would be nice sometimes Mike.

MechDiver

March 5th, 2003, 03:13 PM

chickdiver once bubbled...
Mech-

Im not familiar with IANTD or TDI's standards or class structures. The difference re: 50/50 or O2 for a single deco gas may be regional? In Florida I have never seen anyone use 50/50 for a single deco gas dive.....

Chick,

Part of the reason here may be the difficulty in finding a fill for anything over 50%. There is one shop I am aware of east of the Cascade Mountains that fills over 40%, and few in the Seattle area that go any higher. We haven't gone home brew yet, but we've started ordering whips.

I also agree with padiscubapro that, if carrying one deco bottle, I would much rather have 50% than 100.

MD

MikeFerrara

March 5th, 2003, 03:14 PM

Per IANTD standards all confined water skills must be completed prior to any OW dives. Also no dive can be more than 33 feet deeper than the students deepest. I agree shallow is where you learn new skills. Deep is where you gain experience.

WreckWriter

March 5th, 2003, 03:21 PM

chickdiver once bubbled...
The difference re: 50/50 or O2 for a single deco gas may be regional? In Florida I have never seen anyone use 50/50 for a single deco gas dive.....

When we dive a single deco gas we also generally use 50% over 100%. In most cases it will get you out of the water faster.

Obviously one will use more of the 50% than one would of the 100% but if you're doing that much deco you should be using two gasses anyway.

That's the way the circle of folks I dive with do it anyway.

WW

ericfine50

March 5th, 2003, 03:51 PM

So, what do people look for in a mix class? Size, gas choices, location? DIR, non DIR, get the card to get the gas to do the dives correctly?

Thanks
Eric

MikeFerrara

March 5th, 2003, 04:23 PM

I have given that alot of thought lately. I have a IANTD Normoxic Trimix card. I own the shop so I sell myself whatever gas I think is best for the dive. I haven't done anything below 200 ft but I use 2 deco gases (and a stage) often and I use mixes with more He and less O2 than what IANTD specifies for normoxic trimix. The only reason I would ever need another card is if I ever want to do a dive and a boat skipper wants the plastic.

If and when I decide to get an "Advanced or Full" Trimix card I have two choices. I can go buy the card over a weekend and pretty cheap at that or I can look for a instructor who could teach me something and take me on some real neat dives. So here is what I think...If I schedule a wreck dive this spring at say 180 and I want to use 18/45 and someone wants to see a card then I'll go buy one. BTW this is a dive I have already done a bunch of times. The depth is within my training (cert) but strictly speaking the mix is not. OTOH, if I have the time, I will go to Florida somewhere just to do a class and dive some real neat caves and/or wrecks and just kick back and enjoy the class.

When it comes to mix I can understand different ratings for different depths but different ratings for different gasses don't make any sense to me.

ericfine50

March 5th, 2003, 04:33 PM

Mike,
I agree. I would like to take a Tech 1 or another mix class. I would like to get the best training possible and get the "card" so I can get He and do the deeper and "wennie" dives with the correct gases.

Eric

MechDiver

March 5th, 2003, 04:39 PM

MikeFerrara once bubbled...

use 18/45 and someone wants to see a card then I'll go buy one. BTW this is a dive I have already done a bunch of times. The depth is within my training (cert) but strictly speaking the mix is not

All you would have to do is call the mix 19/45 and you would be okay. Is that not correct? We had to use 19% or above to meet class specs for IANTD, but I kind of infer from postings here that 18% is still considered a surface mix and would be covered under the term "normoxic".

Although I pretty much agree with you, the benefit I would expect to see with a full trimix class would be more info on stage diving and travel gas usage. Although neither seems to be that tough to figure out, below 200 fsw is not the place to experiment IMO.

MD

MikeFerrara

March 5th, 2003, 05:07 PM

MechDiver once bubbled...

All you would have to do is call the mix 19/45 and you would be okay. Is that not correct? We had to use 19% or above to meet class specs for IANTD, but I kind of infer from postings here that 18% is still considered a surface mix and would be covered under the term "normoxic".

Although I pretty much agree with you, the benefit I would expect to see with a full trimix class would be more info on stage diving and travel gas usage. Although neither seems to be that tough to figure out, below 200 fsw is not the place to experiment IMO.

MD

Actually the way the IANTD standards read no more than 30% He can be used in the class (don't ask me why). I don't know what someone will actually sell you. Most of my recent cave dives are stage dives. If I need a travel gas I just use my 50%. The leanest mix I have ever used was ok to breath at 7 ft anyway. Too me the issue is depth not mix. There isn't much difference between a 200 and a 230 but a 330 is something else. I'm not getting any yonger and I'm not out to set any records so it may be a nonissue. Our dives are already as much as we can take given the temperature.

chickdiver

March 5th, 2003, 05:19 PM

Mike,

I agree with you (mostly). I think the arbitrary depth and/or mix limitations are a crock. If you understand the math for trimix at 190' then you understand the math for trimix at 290', etc.; the same thing applies with procedures and decompression. However, mental preparation is a lot tougher for the deeper dives (over 250' in my opinion), and you also have to be dead on with the skills and the contingency plans, because there isn't as much time when things start to go wrong. I think that for the deeper dives expereince is the key. I don't think that most dives conducted in a "training" guise are very good for building that kind of expereince. To gain that expereince you have to be out there doing progressively more challenging dives with a group of people who know thier stuff- int hat case I think mentoring is really the key.

MechDiver

March 5th, 2003, 05:22 PM

MikeFerrara once bubbled...

Actually the way the IANTD standards read no more than 30% He can be used in the class (don't ask me why).

True, but I have seen nothing that says once you are out of the class that you are still "limited" to 30% He. Would make no sense anyway. As you have a shop, do you limit mix fills to 30% for anyone holding a normoxic card?

MD

O-ring

March 5th, 2003, 05:24 PM

MechDiver once bubbled...

True, but I have seen nothing that says once you are out of the class that you are still "limited" to 30% He. Would make no sense anyway. As you have a shop, do you limit mix fills to 30% for anyone holding a normoxic card?

MD
I would be curious what your procedures (and others' procedures) are for people holding depth limited cards. For example, will you not sell a customer a mix that is intended for use deeper than a customer's card permits? (i.e. would you sell a Tech 1 cardholder 18/45?).

MechDiver

March 5th, 2003, 05:38 PM

O-ring

March 5th, 2003, 06:50 PM

MechDiver once bubbled...

What is the depth limit for Tech 1? Is that the 165' that Pug mentioned?
..at least that's what the site says...I thought it was 130'.

MechDiver

March 5th, 2003, 07:04 PM

O-ring once bubbled...

..at least that's what the site says...I thought it was 130'.

Concerning your other question, I called a shop in Seattle and could get 18/45 using my IANTD card. Technically that is within my training guidelines, although the 18% is fugded a little. I was concentrating on the He content and did not directly ask about a hypoxic mix. He said they sell alot of 16/60 and mix what is asked for.

MD

MikeFerrara

March 6th, 2003, 12:53 AM

chickdiver once bubbled...
Mike,

I agree with you (mostly). I think the arbitrary depth and/or mix limitations are a crock. If you understand the math for trimix at 190' then you understand the math for trimix at 290', etc.; the same thing applies with procedures and decompression. However, mental preparation is a lot tougher for the deeper dives (over 250' in my opinion), and you also have to be dead on with the skills and the contingency plans, because there isn't as much time when things start to go wrong. I think that for the deeper dives expereince is the key. I don't think that most dives conducted in a "training" guise are very good for building that kind of expereince. To gain that expereince you have to be out there doing progressively more challenging dives with a group of people who know thier stuff- int hat case I think mentoring is really the key.

No argument here. Thats why I say that too me the limiting factor is depth/time not gas. As far as I'm concerned depth/time increases risk and makes precision more critical. I also agree that depth and time should be increased gradually. It's better to make little mistakes on short shallow dives than on long deep ones making a little mistake a big one.

MikeFerrara

March 6th, 2003, 01:00 AM

MechDiver once bubbled...

As you have a shop, do you limit mix fills to 30% for anyone holding a normoxic card?

MD

Not that I have a line of divers witing for trimix fills (I am by far my best customer) but I guess I'll do what makes sense to me at the time. I know that isn't much of an answer but that's the best I can do. On another note all the mix divers I know mix it themselves.

MikeFerrara

March 6th, 2003, 01:13 AM

O-ring once bubbled...

I would be curious what your procedures (and others' procedures) are for people holding depth limited cards. For example, will you not sell a customer a mix that is intended for use deeper than a customer's card permits? (i.e. would you sell a Tech 1 cardholder 18/45?).

See my post above. I don't know what the limits of a tech 1 are. Within reason I certainly wouldn't want to tell someone what gas they should use for a dive. It's a little obviouse that a card that says "normoxic" on it wasn't intended as a ticket to get 10/70. On the other hand if a guy wants 18/? to keep his PPO2 down on a long dive should...? I have to baby-sit OW divers I'm not going to get in the habbit of watchinh technical divers. Within reason I'll do what makes sense.

ericfine50

March 6th, 2003, 08:55 AM

O-Ring,

I think GUE is still playing with the Tech 1 depth limit. Tri-Ox is rated to 120, so I am not sure if they are going to stay with the 150 or move it to 165? Do you think people will want to take a Tech 1 that is rated to 150? Don't know, just throwing out questions.
Eric

O-ring

March 6th, 2003, 10:37 AM

ericfine50 once bubbled...
O-Ring,

I think GUE is still playing with the Tech 1 depth limit. Tri-Ox is rated to 120, so I am not sure if they are going to stay with the 150 or move it to 165? Do you think people will want to take a Tech 1 that is rated to 150? Don't know, just throwing out questions.
Eric
..the 130' limit was before triox, so maybe they are reworking some of the standards and procedures since, IMHO, it doesn't make sense to have triox at 120' and then tech 1 at 130'. Then again, triox doesn't teach deco...who knows?

Uncle Pug

March 6th, 2003, 11:42 AM

Our final dive of Tech 1 was to 165'.

The card we received from GUE says, among other things:
Tri-Ox (150ft)

Shane and I dive to 165'.

cdtgray

March 6th, 2003, 12:14 PM

Once again the DIR crowd has taken over a thread. The original questions posted by cadet diver have nothing to do with what DIR considers to be acceptable depth limits for their Tech 1 class.

Cadet diver asked if:
1. A dive to 200 fsw for 15 min. on 21/35 with a single deco gas of 50/50 has been common for anyone else on the board.

2. If anyone has had problems getting appropriate sized stage bottles in the Bahamas.

The first question was answered well in that the depth/time seem about right and the use of just 50/50 may be preferable to 80/20 or O2 if only one deco bottle is available. Also that 21/35 may be a little hot, but fits within TDI guidlines and has been done by others on the board.

No one has given any info regarding the second question.

While I have nothing against DIR and those whose choose to adhere strictly to DIR principles, I do have a problem when every post on this board turns into a DIR discussion.

Uncle Pug

March 6th, 2003, 12:37 PM

cdtgray once bubbled...
I do have a problem when every post on this board turns into a DIR discussion.
While I am truly sorry for the distress this has caused you... it is quite common for threads to meander off of the original topic, especially after several pages... and since we have quite a few folks on this board who are interested in DIR that topic does come up in a lot of threads. I think you will find that accepting that fact will go a long ways to relieving your angst.

BTW.... if you have an answer for #2 please feel free to contribute.

cdtgray

March 6th, 2003, 12:45 PM

No I do not have an answer to question #2. I'm going on the trip with cadet diver.

WreckWriter

March 6th, 2003, 12:50 PM

The answer is that you'll probably have trouble getting 40s but 80s will be available pretty much anywhere. To some extent this will depend on exactly where you'll be. There may be a few places where 40s are available.

WW

MechDiver

March 6th, 2003, 12:58 PM

cdtgray once bubbled...
Once again the DIR crowd has taken over a thread. The original questions posted by cadet diver have nothing to do with what DIR considers to be acceptable depth limits for their Tech 1 class.

Cadet diver asked if:
1. A dive to 200 fsw for 15 min. on 21/35 with a single deco gas of 50/50 has been common for anyone else on the board.

2. If anyone has had problems getting appropriate sized stage bottles in the Bahamas.

The first question was answered well in that the depth/time seem about right and the use of just 50/50 may be preferable to 80/20 or O2 if only one deco bottle is available. Also that 21/35 may be a little hot, but fits within TDI guidlines and has been done by others on the board.

No one has given any info regarding the second question.

While I have nothing against DIR and those whose choose to adhere strictly to DIR principles, I do have a problem when every post on this board turns into a DIR discussion.

I kindof meandered the thread because the question of what the "acceptable" mix was for a normoxic cert diver. It had nothing to do with DIR, nor did any of the responses. The depth question was, again, in response to mix content and was actually directed at a shop owner for his input.

I didn't even notice the part about the tanks.

BTW, you might want to get a rather thick wetsuit to protect that fragile skin of yours. And no, I am not "DIR", but thanks for asking...

MD