How rare is extended range trimix?

[ucfdiver]

Sure. However he had stated that there wasn't a difference planning a 300' dive vs a 150' dive. Gas selection is a part of dive planning. When planning a 150' dive ibcd is less of a concern given that you'd be breathing a pretty light trimix... It does play a role in your planning for a 300' dive...


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I've yet to see or hear of an example where reasonable gas choices were made that ICD is an issue.

 

[drice]

And my point is making those reasonable gas choices are part of the planning. Which is where a 150' dive and a 300' dive differs.


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[ucfdiver]

And my point is making those reasonable gas choices are part of the planning. Which is where a 150' dive and a 300' dive differs.

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Just curious, what type of profile would you be worried about ICD if you kept your END below 80-100ft for all gases (including deco gas)?

 

[kwinter]

I think the point is that you should have some knowledge of what ICD is if you are going to do hypoxic deep dives. Planning for a 300 foot dive must take ICD into account whereas it might not even be discussed in a normoxic course. I know it wasn't in mine.

 

[ucfdiver]

I think the point is that you should have some knowledge of what ICD is if you are going to do hypoxic deep dives. Planning for a 300 foot dive must take ICD into account whereas it might not even be discussed in a normoxic course. I know it wasn't in mine.

I guess what I'm asking, is if someone who learned not to have an END >80-100ft (day 1 lecture 1 normoxic trimix) would ever have issues with ICD if they followed the END guidelines set forth in their normoxic course.

 

[drice]

Just curious, what type of profile would you be worried about ICD if you kept your END below 80-100ft for all gases (including deco gas)?

Sure. Use a bottom gas of 12/65 to 330' (your END at 330' will be 94') with gas switches to EANx36 at 100' and O2 at 20'. At all times, your END is no greater than 100' but you risk an ibcd hit at 100' when you do your first switch.

 

[Germie]

ICD is normally not an issue in a normoxic dive. For example, if you do a 60m dive, 20-25 minutes bottomtime (200ft I believe), you can use 18/45 as bottomgas (officially not for all agencies normoxic, but normally you can get that gas with a normoxic cert). Then you take a 50% and a 100% as decogas.

The switch from 18/45 to 50% does not follow the 5:1 rule for icd, but this switch with a maximum depth of 60m can be done.
If you come from 100m or more and want to do some bottomtime (remember icd has to do with delta P, so it has to do with amount of saturation too), then I will put some helium in the 50%, let’s say 50/20, even if I use a 18/45 as intermediate gas. So then the switch will be 18/45 -> 50/20 or so. Not to only a EAN50.

 

[ajduplessis]

Don't even bother going down that path. The clever guys here will tell you ICD is a nonevent that shallow, while others will tell you how they dive the mentioned profile 100 000 times without any issues.

 

[ucfdiver]

Sure. Use a bottom gas of 12/65 to 330' (your END at 330' will be 94') with gas switches to EANx36 at 100' and O2 at 20'. At all times, your END is no greater than 100' but you risk an ibcd hit at 100' when you do your first switch.

This, too, violates what you're taught in a normoxic trimix class. No well trained normixic diver would agree to a dive profile where they have to ascend 230ft before their first deco gas. The minimum gas requirements for a dive like that would be absurd. If you don't believe me, run a profile for that dive where the 100ft bottle fails and let me know how that works out.

I'll ask again, can you pick proper gases and still be at risk for ICD?

 

[PfcAJ]

Ibcd is a real thing, for sure. But if you pick smrt gases isn't not. It was briefly discussed in my t2 class, but the gue standard gases really make it a non issue.

Im in sure you can contrive some sort of gas plan that would put you at risk for it, sure.