wedivebc

I have this friend who came to my house the other day to borrow my helium analyzer. I was on my way out for a dive myself but he came by early enough I was still packing up. I walked the analyzer to the back of his truck and as he analyzed a dil bottle of 11/54 and an 80cuft of 11/57 I casually asked him "where are you diving?". He was heading out with some others (newbie CCR divers) to do a 90ft (27m) shore dive on a really nice wall. I asked him why the gas choice? He replied he always uses these mixes but had been backfilling so needed to analyze since he was unsure of the mix.
This guy is OC trimix trained (not by me) and I really don't like to be a know it all (at least not usually) but I really am worried about a guy using weird mixes like this for no apparent reason. I would like to hear comments from the RBW community about these gas choices.

__________________
Cheers,

Dave....

www.wedivebc.com

icestac

Just a benefit of the doubt post, but could it be that he is just topping off old fills with pure HE? Seems like if he had some 24% and boosted a little over 1/2 a tank of HE, he would end up with such a mix. He may just not know a better way to get the mix (and has WAAAY too much money :)). Perhaps he just needs a little talking too.

Cheers,
Jeff

19Hunter68

Just sayin.

kwinter

Bailout pO2 of 0.4 and it will drop as he ascends. I sure hope he's got another gas with him. If it's 100%, then his bailout will drop to 17.6% before he can switch to the O2.

Survivable, but certainly not optimal. Lend him some more tanks so he doesn't have to just live with what's in those.

Ken

Drmike

edited: should have read the post better

Joshua Smith

Dave- I'm confused. Is this guy a CCR diver? You said he had a dil bottle, so, I presume he is.

If so- 11/54 dil: I know a lot of people using hypoxic dilluent for every dive. I used to do it, too, just in case I wanted to do a spur of the moment deep dive. Pretty much always used to use 10/50, but these days I have extra tanks, so I keep one set full of something like 16/40, and another with 10/50 ish.

The bailout is more of a concern. 11/57? I would carry an 80 of 40% for a 90' dive- or 2 al 40s, 1 with trimix and the other with nitrox, depending on the dive. 11/57 is straight-up crazy for that dive.

__________________
-Joshua Smith, Seattle, WA

wedivebc

Yes CCR diver. He did indicate another, richer bailout gas was also being used. I am concerned that he is diving with newer CCR diverswho are not trimix divers, he is not a CCR trimix diver. I have tried to talk to him in the past about this issue but he isn't getting why I am concerned.
When I select a bailout gas, since I seldom dive solo my bailout is expected to be available to use by any one diving with me. That is why I have an OC regulator attached even though I dive with a BOV. If my shared regulator is attached to a hypoxic mix am I exposing others who may be unfamiliar with the dangers of these gas choices to unnecessary risk? What about hypoxic dil, what reason would someone use it for a shallow dive?
Josh, dives requiring 10/50 mix are pretty deep to be doing spur of the moment don't you think?
Personally I only use hypoxic mixes on a dive that truly calls for it. I would never carry a hypoxic gas when diving with someone who is not trained to use it as well. I just see too many pitfalls here.

__________________
Cheers,

Dave....

www.wedivebc.com

Joshua Smith

I see your points- I used to use hypoxic dil....well, mostly because I could. Partly because I only had one set of tanks for my Meg at the time, and I knew I was wearing a gas blending station on my back. And I wasn't blending my own gas, like I do now, so fills were a bit of an ordeal- 2 hour drive to the shop to drop off one day, 2 hour drive back a day or so later to pick up. I knew that if I filled up w/ 10/50, I could do most any profile me and the idiots I like to dive with could dream up. I've changed my thinking about this- It occurred to me one day, swimming back to the boat in rough seas- that a good dil flush could possibly kill me. (especially on the COPIS)

One thing that I've noticed is that some experienced OC trimix divers sometimes make poor choices regarding CCR bailout gasses. I saw a guy do a 330' wreck dive with an AL80 of 10/70, another of 21/35, and another of 100%....it just didn't add up for me. I think he hadn't done the math. CCR bailout- if you're not in a cave- shouldn't have much bottom time involved.
I like to tweak my gasses to allow some time to get sorted if need be- but if I've bailed off the loop, I'm going back up as fast as I can safely, reasonably, do so.

__________________
-Joshua Smith, Seattle, WA

Drmike

hes mix OC trained - so he should know not to bail to a hipoxic (at that depth) gas. any fo2 is fine as a dil - just that shallow low fo2 dils can be a pain in the but on a shallow reef dive with up and down profiles on eccr - burn through a lot of gas and bouyancy is more work

Drmike

couldnt disagree with you more.

im of the school of thought that if you bail (from a co2 hit) its likley that your deep and your rmv will initialy be high. best you have heaps of deep bailout gas so you can sort out your rmv and recover without the additional stress/worry potentiality of running low/out. also one should resist the temptation to imediately ascend when you have issues (knowing you have a tiny bottom bail tank wouldnt help discourage this). Stop, focus on lowering rmv get your sh1t together, then decide on the next step.

in addition if on a wreck and you bail the last thing id want to do is start to imediately ascend possibly on my own, possibly in strong currents and low viz. nobody knows ive got an issue, i could run out of gas, or start to tox or whatever - all alone. get to security of the upline get to your buddies (more gas). Basically- get help, then ascend at a fixed point to the boat where people can keep an eye on you/bring you more deco gas, up the safety of the upline.

(i recall doing a long dive at eagles nest with cedric and his wife, and due to him having left some of the shallow deco tanks at dive outpost we were 'forced' to come up with a daft plan for bail. if one of us bailed we determined we had enough bail gas amongst us for him to get back and up to 12m. At 12m he would stay until the Rebreather divers finished all their deco then he would swim up and get into the Rebreather of the exiting diver and finish deco on his Rebreather.....dont try this at home ;) The point is shallow where gas consumption is low you have time to sort out any issues with shallow deco bail. ) where you mustnt skimp is deep bail volumes.


if diving under a boat you have time before you need shallow gas, time to alert support crew or buddies to help send down more shallow gas. same is not true of deep bail gas. if you cant get enough deep bail gas when you need that....your done.


remember if you dont have enough gas to recover from the initial rmv of a co2 hit at depth.....you wont need anymore shallow gas as youll be dead... and if youve ever had a co2 hit you know just how fast you can suck dry a AL80.......