does it make sense to dive trimix in single tank

[nadwidny]

i've done it

But did it make sense?

 

[LiteHedded]

But did it make sense?

of course it made sense, I did it.

 

[MXGratefulDiver]

I thought of that for a moment, but it was a steel tank. Either HP100 or LP80/LP77 kind of size. That is why I don't think it is a stage or deco bottle. Too big for rebreather too.

I know a few RB divers who use an HP100 for bailout. If you're diving cold water and wearing a lot of undergarment underneath your drysuit it makes sense. SF water's not very much warmer than where I dive.

Is 30/30 really that different from 32% nitrox at 100ft?

From a narcosis standpoint, yes ... but it depends on the person. Some folks don't feel very narc'd on EAN32 at 100 fsw. I don't ... 120 is a very different matter, however, and I won't go below that depth without some helium in my tank(s) ...

... Bob (Grateful Diver)

 

[PfcAJ]

I'd do 3030 in a single tank for a deeper dive, sure.

 

[parzdiver]

I have heard that diving 30/30 in the 100 foot range gives a new perspective on just how narc'd people are and they don't realize it.

 

[Captain_Bob]

drysuit inflation maybe?

I would hope they are not using it for drysuit inflation. That would make for one COLD dive. Helium does not provide insulation well. I have many times put trimix in a single tank. I've used it for stages, sometimes decompression, side mount and rebreather bailout. So yes there are many reasons it makes sense to put Trimix in a single tank.

 

[eelnoraa]

drysuit inflation maybe?

I guess not. Not with He in it. Plus, even LP77 is way way too big for drysuit inflation.

I know a few RB divers who use an HP100 for bailout. If you're diving cold water and wearing a lot of undergarment underneath your drysuit it makes sense. SF water's not very much warmer than where I dive.

At least what I was taught, stage/deco bottles should NOT be part of our ballast when weighting. Backgas is OK. This is because you may hand off the bottles to someone, or even lose a bottle in mid dive. You don't want to be underweighted if that happens. I think this is a common pratice, right?

I have heard that diving 30/30 in the 100 foot range gives a new perspective on just how narc'd people are and they don't realize it.

Maybe I need to try a tank. It will be an expansive rec dive

 

[MXGratefulDiver]

At least what I was taught, stage/deco bottles should NOT be part of our ballast when weighting. Backgas is OK. This is because you may hand off the bottles to someone, or even lose a bottle in mid dive. You don't want to be underweighted if that happens. I think this is a common pratice, right?

Since this is the DIR forum the answer is yes ... that is the DIR answer. However, my comment was about RB divers ... who are unlikely in the extreme to be handing off their bailout gas to someone else. RB divers each carry their own bailout, and it is not deco or stage gas. ... it's strictly for if they for some reason have to come off the loop.

... Bob (Grateful Diver)

 

[lamont]

(moved thread out of DIR forum)

 

[pensacolaracer]

It is not uncommon for elite spearfisherman in these parts to introduce some He into their amply filled LP120's, Etc. for a more productive and safer deep dive...

Exactly! I would not call myself an "elite" spearfisherman, but I used to routinely dive the Guy Harvey in 145 FSW as a no deco dive with 25ish percent Nitrox. I was not down long, but when hitting a wreck to see if there is anything worthwile omn it to shoot, you don't need to be down long.

After I got Trimix certified, I decided 135 was my limit for not putting Helium in the mixes (one of my favorite wrecks is at 135). So if I ever dive the Guy Harvey again on a single tank for spearing, I will have some Helium in the tank.