Bailout Gases for long 60 metre dives

lbihler

big oooopps , definitely a good point I never took into account
Thanks

Mark Chase

Personally i wouldn't bailout to air from trimix at 60m. You will possibly be breathing like a train and spiking the PP02 from 1.0 to 1.5 but more importantly spikeing the Pn2 from 2.9 to 5.53. This will result in a big wave of narcosis on the already stressed diver and could result in inner ear problems, nausea & dizziness.

2 X 40min 60m dives a day is pushing it as well. Run time will be 2 - 2 1/2 hours per dive. Decoing out on 02 would be advisable to clear the body fully but you would need to keep track of CNS. Too much drama for me Either do one dive or cut the bottom time.

ATB

Mark Chase

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lbihler

OK for narcosis, my mistake won t do it again.

Run time is usually around 2 1/2 to 3 hours per dive and I do deco on pure O2 at the deco bars (I do not mind spending time in the water).
CNS is OK, just about 2 5min air breaks when I pas 100% do the job well (I only pass 100% on the second dive though).
As it is on a liveaboard (in warm water by the way, 29-30 degrees celcius whole the way), I got a nice 4 to 6 hours surface interval in between dives.

I do not think it is pushing it too much, I feel well after the dives, not too tired or anything so ...
Only problem, I hate peeing in my wetsuit and with this kind of run times,...... I usually have to

Mark Chase

Would you like to put down the maths on here for the 24 hour cumalitive CNS loadings for two 2 1/2 hour dives decoing out on pure 02?

I reckon the second dive will be off the scale for 24hour exposure.

If this is a multi day thing you will be realy pushing it by the end of the trip.

ATB

Mark Chase

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Gibbon

Pee - zip every wet suit should have one.

If you take into account the 90 minute half life of CNS on the surface breathing air then you would not be so concerned?

SteveL

Ok guys just curious here -

Most of us have had to get off the loop and grab a few mercy breaths from time to time for one reason or another

- BUT my question is how many of us have had a catastrophic loop failure that has required OC bail out all the way out ?? That doesnt mean running semi closed but completly flooded and or useless loop -

Maybe a good poll topic - I be curious to see if all this bailout statistically gets used - I've had to my share of mercy OC breaths but I like to get back on the loop SCR or CCR asap -

Just curious

Steve L

decoweenie

I have a hypothetical question...

If only 1% of the CCR dives resulted in requiring OC-bail-out from the bottom to surface, how many people would be willing to accept this risk for the sake of diving uncumbered without stages knowing that if they have a loop flood, they will die ?

That means 1 in 100 dives, so could be a high percentage. So let's reduce to 0.5%, that means 1 complete loop flood in 200 dives.

Or let's say 1 in 500 dives ? Remember it could happen anytime between dive 1 and 500..

Who would take this risk ?

I know a few alpinist divers. Some are just lazy and complacent, but some are fully aware of the risk but willing to accept the percentage.

I know you didn't ask about alpinist, but IMHO, there is no such thing as semi-alpinist (i.e. like semi pregnant) so either you have adequate OC bail-out or you don't. So having a small amount of off-board gas just to take "sanity breaths" is alpinist in my book.

What would someone do when after taking a few sanity breaths, they realize that they can't get back on the loop and not having adequate OC-bail-out ?

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Mark Chase

Yes but working on a avg of 1.3pp02 for the dive over 150 -180mins even on 150 he will hit 300mins when the recomended max exposure limit for a 24 hour period is 210. So he is getting on for 27% over. For 2X3 hour run he is looking at 360mins.

Or are we saying that the NOAA Daily Oxygen Presure time Exposure limits are rubbish?

ATB

MArk Chase

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iani

I've had two complete floods out of the last two dives! it can happen.

Ian

(I am somewhat concerned about this Sunday's post factory trip test dives)

viscya

Mark

I'm not sure where your runtime numbers are coming from, but V-planner is giving me less than 100-120 minute runtimes depending when you bump up the PPO2. Personally I'd stick with PPO2 of 1.1 the whole dive and take 118 minutes to surface. This is 50% CNS per dive, and the daily limit is below the 270 in the NOAA spec.


Phi,

I've had enough flooding in the loop to make the WOB intolerable. I'll carry bailout!

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