Trimix Max Depth

[Teller]

I am taking the PADI Tech 40 class in a few weeks and I have been looking at the Trimix class. I know it will be quite a while before I am ready for trimix but I was curious. My question is this, PADI say something like 190 feet is your max depth with trimix. I think TDI site said over 300 feet was you max depth with trimix. I know nothing about tech diving yet but am I missing something. Is there different types of trimix?

[sea2summit]

PADI takes you to 245'. It used to take you deeper I think with DSAT I'd have to look. When you start doing depths beyond 200' it's pretty rare to get carded, someone else has to vouch for you or you need a few dives on the boat.

[tkdgodess]

There are steps in the padi courses. If you do all the courses to tec trimix diver the padi site says "training dives to 245'" for tec trimix diver. Tech 40 is the first step in the padi tech courses. I've seen a chart showing min & max depths allowed for each course offered.

[SteveAD]

short answer: yes

just like there is more than one type of nitrox

Big picture there are 3 classes of trimix: hypoxic (less than 21% O2), normoxic (21%O2) and hyperoxic (greater than 21%O2)

190 feet would be the approximate mod for normoxic tmx as the ppo2 for 21% hits 1.4 ata at 186 feet.

Reducing the FO2 increases the MOD, but a mix with an extremely deep MOD can result in a mix that will not be breathable at shallow depths.

Hyperoxic trimix is frankly a kind of silly idea because anywhere a >21%O2 mix could be used He is probably not required.

[Teller]

short answer: yes

just like there is more than one type of nitrox

Big picture there are 3 classes of trimix: hypoxic (less than 21% O2), normoxic (21%O2) and hyperoxic (greater than 21%O2)

190 feet would be the approximate mod for normoxic tmx as the ppo2 for 21% hits 1.4 ata at 186 feet.

Reducing the FO2 increases the MOD, but a mix with an extremely deep MOD can result in a mix that will not be breathable at shallow depths.

So if I understand right it sounds like PADI uses normoxic trimix and TDI uses hyperoxic trimix. Is that correct and if so, what if I do the PADI course and I decide I want to use hyperoxic trimix. Do I have to take another class or is a trimix diver a trimix diver. Thanks.

[Cave Diver]

So if I understand right it sounds like PADI uses normoxic trimix and TDI uses hyperoxic trimix. Is that correct and if so, what if I do the PADI course and I decide I want to use hyperoxic trimix. Do I have to take another class or is a trimix diver a trimix diver. Thanks.

Hyperoxic means having an elevated oxygen content.

Hypoxic is a reduced (from normal/normoxic) oxygen content.

Hypoxic Trimix is generally a different class than Normoxic Trimix, depending on agency. Training limits on this are generally 330' or less.

IANTD also offers an Expedition Trimix course for planning dives in the 330-400' range.

[sea2summit]

So if I understand right it sounds like PADI uses normoxic trimix and TDI uses hyperoxic trimix. Is that correct and if so, what if I do the PADI course and I decide I want to use hyperoxic trimix. Do I have to take another class or is a trimix diver a trimix diver. Thanks.

There's steps to the cert, first one is normoxic (stuff you could breath at the surface and not pass out) then various stages of hypoxic (stuff that will give you altered states of conciousness, or lack there of, at the surface). Padi does the 40, 50, 65 or something like.

[TSandM]

There is no depth limit to what you can do on trimix, although there appears to be a practical limit on what you can do on scuba, OC or rebreather, at somewhere around 1000 feet. You change the proportions of oxygen, helium and nitrogen as the depth of your dive changes. Classes are broken up into depth limits, mostly having to do with gases used and the number of deco bottles. For example, GUE Tech 1 is for dives in the 150 foot range (21/35 and one deco bottle). Once you get to dives where your ppO2 on 21% is too high, or where you need to add another deco gas, that's a different class. So the limits are only partly on mix, but also on complexity of the dive.

[Red Sea Shadow]

So if I understand right it sounds like PADI uses normoxic trimix and TDI uses hyperoxic trimix. Is that correct and if so, what if I do the PADI course and I decide I want to use hyperoxic trimix. Do I have to take another class or is a trimix diver a trimix diver. Thanks.
I think PADI (DSAT) has a hypoxic class as well.

TDI Trimix classes are split into two; Trimix Diver and Advanced Trimix Diver. Trimix Diver class uses normoxic mix while the Advanced one uses hypoxic mix.

[StreetDoctor]

For all intensive purposes 18/45 is considered a normoxic mix also because it is breathable on the surface. You have to look at the ppO2 of the gas (example GUE wants you to stay below 1.2 for the working portion of the dive) and the END (narcotic depth of the gas) no deeper than 100'. The deeper you go the more complicated your decompression gets along with using travel gases, stage bottles, etc.

[Scott L]

I smell another deep air thread brewing...:shocked2:

[ianr33]

Is there different types of trimix?

Yes.

Expensive trimix and really really expensive trimix :D

TDI at least has 2 training levels.
1)Trimix. Max depth 200 ft. Minimum O2 18% (Close enough to normoxic)
2)Advanced Trimix. Max depth 330. this will use hypoxic mixes.

Deeper than 330? Hopefully you can figure it out for yourself by then.

[captndale]

Deeper than 330? Hopefully you can figure it out for yourself by then.

Exactly. At this level, if you think you need some kind of certification you definately are not ready to do the dive. Asking the question is a disqualifier.

[Cave Diver]

Deeper than 330? Hopefully you can figure it out for yourself by then.


Exactly. At this level, if you think you need some kind of certification you definately are not ready to do the dive. Asking the question is a disqualifier.

The expedition trimix course (330'-400') addresses things like support personnel and safety divers. Not all mixed gas divers are familiar with these additional aspects.

[ianr33]

What if I need to do 401' ? :D

As captndale said, although it might be nice to have these courses around I hope they never become compulsory .

[Cave Diver]

What if I need to do 401' ? :D

As captndale said, although it might be nice to have these courses around I hope they never become compulsory .

Take the same gas that you would for 200.5', just twice as much of it. ;)

Agreed about the compulsory, but I won't dismiss the idea of more advanced training just because I already have some. I know how to plan gasses, deco schedules, etc. for sub 300', but I think the information on safety divers and support personnel could be worthwhile.

[roturner]

There is no depth limit to what you can do on trimix, although there appears to be a practical limit on what you can do on scuba, OC or rebreather, at somewhere around 1000 feet.


One of the practical limits is that the current deco models all seem to be inadequate for calculating deco on really deep dives. Aside from the practical/logistical problems most of the really deep divers get physical problems. Nuno Gomes usually goes deaf for a while after his really deep dives, Mark Ellyatt has totally gibbled his lungs and has a cough that won't stop... etc. etc. From what I've been told few dives >250m are free of physical symptoms.

If you put it all together, the difficult logistics, the physical issues, the increasingly experimental nature of dives deeper than about 100m, I'd say that a reasonable "practical" limit for scuba diving must be in the 100m range.

R..

[Rhone Man]

On DMX Joel Silverstein posted in a thread that if you want to be diving deeper than 250', you really ought to be on a rebreather.

Whilst not completely signing up to that comment, I can see the force of what he says.

Must be what PADI was thinking...

[ianr33]

On DMX Joel Silverstein posted in a thread that if you want to be diving deeper than 250', you really ought to be on a rebreather.

Whilst not completely signing up to that comment, I can see the force of what he says.

Must be what PADI was thinking...

How much will they be charging for their rebreather courses ? :D

OW rebreather diver
AOW rebreather diver
Night rebreather diver
Boat rebreather diver etc etc etc

[sea2summit]

On DMX Joel Silverstein posted in a thread that if you want to be diving deeper than 250', you really ought to be on a rebreather.

Whilst not completely signing up to that comment, I can see the force of what he says.

Must be what PADI was thinking...

I think this makes a lot of sense. My first dive in eagle's nest that's all I thought the whole dive "the guys that mapped this OC often on air have way bigger (*lls than I do".

But it swings back to OC deeper, because you have to suck that gas through the loop I'm sure there is a point where it makes sense, physically not logistically, to go back OC.

[sea2summit]

How much will they be charging for their rebreather courses ? :D

OW rebreather diver
AOW rebreather diver
Night rebreather diver
Boat rebreather diver etc etc etc

Hey there is already a "recreational rebreather" certification out there. Whatever that means.

[ucfdiver]

Hey there is already a "recreational rebreather" certification out there. Whatever that means.
That means they looked cool and the diver had the money :popcorn:

[ianr33]

That means they looked cool and the diver had the money :popcorn:

Operative word being "had" :D

[wedivebc]

Operative word being "had" :D
You think rebreathers are expensive, try owning a boat.

[Scott L]

You think rebreathers are expensive, try owning a boat.

That's what friends are for...:)

[Colliam7]

My question is this, PADI say something like 190 feet is your max depth with trimix. I think TDI site said over 300 feet was you max depth with trimix. ... Is there different types of trimix?As mentioned, I suspect the 190 ft depth limit was not for 'trimix' in general but rather for normoxic (21% O2) trimix, where the MOD is ~187 / 190 ft. In the PADI Trimix course you also use different / lower concentrations of oxygen, adjusted for your planned maximum depth. No, you do not necessarily need another course just to use either hyperoxic or hypoxic trimix. However, as several have mentioned, if you reach a point where you are looking at dives in the >300 ft range, there may be a logistics chain for which most trimix courses, including the PADI course, do not specifically attempt to prepare you. The market for tec is relatively small enough, the market for trimix courses is smaller, and the market for divers seeking training to go to more extreme depths (e.g. >300 ft) is sufficiently small, that PADI would probably not consider it a reasonable investment to concentrate on it, UNLESS someone wrote a compelling Distinctive Specialty course outline and application for it.

I took the DSAT Tec sequence, through Trimix. I regularly use normoxic and hypoxic trimix blends, and even use hyperoxic trimix at times. The course prepares you to select a trimix blend for a particular planned dive based on considerations such as maximum depth, and the target END (e.g., no greater than 130 ft) and ppO2 limits, not simply on the basis of a particular blend. The course has recently been revised, to INCREASE the minimum and maximum depths which the diver must be exposed duirng training. For the Tec Trimix course, by the last dive, the minimum depth is now 245 ft, while the maximum depth is now 300 ft.
So if I understand right it sounds like PADI uses normoxic trimix and TDI uses hyperoxic trimix. Not exactly, at least as far as the PADI comment goes. In the PADI Tec Deep sequence, you can now use normoxic trimix on Dive 12 of the course sequence. But, in the PADI Tec Trimix course, you will use different mixtures, including hypoxic trimix. The only limitation in the standards, besides depth, is that the trimix blend use must have at leat 10% oxygen.