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.