Use of 'hot' diluents

Mdemon · 29th January 2007, 10:02

Makes sense to me. Additionally, you're not loading yourself with helium as much which will have an impact on your deco too.

Maybe you should summarise this into a short article Dave? Would save repetitive threads?

Quote: (Originally Posted by Dave Sutton)

Errr..... *nobody* ever suggested diving with a diluent that had a 2.5 or 4.0 PP02 on the bottom so *get real*. Any point can be taken to the area of senselessness. What I *suggested* is that we not switch to hypoxic diluents *unless we need them* and then further suggested that we don't need them as shallow as some think. I fence off my max depth for normoxic diluents when I reach 1.8 PP02 on the bottom, and run 20% dils to the associated depths for that. After that we switch to hypoxic dils. And it's *darned rare* for us to be in the depth band where we exceed setpoint PP02 with 20% and have not yet switched to hypoxic dils. Like 1 in 100 dives......

2.5? 4.0? Nobody ever said that was appropriate. Maybe you got bored and skipped over the technical parts in the earlier series.... and the KISS has a valve on the 02 bottle for a reason......

And the title of the thread is wrong:

NOBODY INCLUDING ME HAS PROPOSED THE DELIBERATE USE OF HOT DILUENTS.

Can I make it any clearer than that?

All I have EVER said is that we should not use hypoxic diluents *unless required* as they:

(1) disallow us certain important SCC bailout modes,

(2) hurt our deco possibilities using our dil open circuit,

(3) have hypoxia/drowning potential if an ADV fails open or we get unwanted diluent into the loop near the surface (and read the current Inspiration thread on that issue it's a REAL one...). And no joke: With the reports of undesired diluent freeflows into the loop, this could KILL YOU RIGHT NOW!

GUYS: If you get an ADV freeflow, (which is *far* more common than many other "silly bordering on insane" hypotheticals than people propose here,) you're not gonna tolerate 10% diluent in your loop on the surface for more than a few *moments* before doing the dead-fly routine *just moments before you drown* after your DSV slips from your unconcious mouth and you loose all of that nice bouyancy in the loop as it floods in about 5 seconds... Trust me on this, *please*?? as I've seen it for *real* (except we dived in and saved his sorry butt and now he buys me beer and mixes his 20% diluent with a smile)

etc.

I also *mentioned* that I will *TOLERATE* (not "desire") diluent that is SLIGHTLY hotter than my desired setpoint *for a certain small fraction of my dives* before I switch to hypoxic diluents for the aformentioned reasons, as I will reduce the PP02 by normal metabolism LONG BEFORE THE CNS CLOCK does jack-shi@ to me. I *personally* use 1.8 as my cut-off, feel free to use 1.6 or 1.4, whatever runs your CNS clock.... Get it?

Dave

Dave Sutton · 29th January 2007, 12:49

Quote: (Originally Posted by chunter)

As to the ADV...it's pretty easy to turn off a diluent valve or have a shut-off to prevent going hypoxic

If you catch it in time... which is not something I would count on. Mere moments at low PP02 is deadly. Long time base on high PP02 is not deadly. I don't see any controversy when selecting between something that will kill me in seconds versus somethign that may cause distress aftr *many minutes*, that's all.

Didn't mean to offend, just that many have not distinguished between accepting perhaps 1.6 as a diluent PP02 on the bottom and doing silly things like using a diluent with a 4.0 PP02 on the bottom. Lack of discrimination of the fine points has been a frustrating experience when trying to explain this system. Did not mean to be snide, just frustrated that some readers (nbot you, obviously) have a hard time dealing with grey areas and the variou shades of grey.

Kind regards to all,

Dave

Dave Sutton · 29th January 2007, 12:54

Quote: (Originally Posted by Mdemon)

Makes sense to me. Additionally, you're not loading yourself with helium as much which will have an impact on your deco too. Maybe you should summarise this into a short article Dave? Would save repetitive threads?

Would be pleased to write an article if the community desires. I can argue the diluent selection matrix from either side, and would be pleased to do so for the edification of all. I'd need to write about SCC bailout modes, VSC bailout modes, and constant bouyancy PP02 control modes too.. as carriage of 02 mixed with diluent gas opens up a lot more doors in the success matrix. Full discussion might tend towards book form, actually...

The helium loading issue is really that of the use of the old "Scamahorn Slide" concepth (thanks to Leon for lending his name), meaning that for the first few minutes after bottoming you are a little hot, meaning that you have less inert gas loading, and then it slides towards more inert and less 02 as you burn te 02 out of the loop. There is a definate deco advantage. The old ZPlan had the option to use a slide for deco, and I take advantage of this using real-time measurement deco calc from my VR-3. The deco advantage can be significant.

Dave

Padowan · 29th January 2007, 14:51

I guess that another nice benefit of a slightly hotter dil is that once you reach your target depth, with a nice high PPO2, you've validated that your cells are capable of showing a PPO2 higher than (most average) SP.

Having done some simulations with regards to depth, dil FO2 and SCR breath cycle modes, a higher FO2 dil will give a considerably extended SCR duration stabilising (at constant depth) at a much more deco beneficial (or perhaps more accurately a less deco loading) level.

jmhardingjr · 31st January 2007, 15:54

Dave,

I'd love to see an article on this method. I heartily second the motion. Hell, write a book, I'll buy it.

Cheers,

Jay

29th January 2007, 10:02	#11 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,906	Re: Use of 'hot' diluents Makes sense to me. Additionally, you're not loading yourself with helium as much which will have an impact on your deco too. Maybe you should summarise this into a short article Dave? Would save repetitive threads? Quote: (Originally Posted by Dave Sutton) Errr..... nobody ever suggested diving with a diluent that had a 2.5 or 4.0 PP02 on the bottom so get real. Any point can be taken to the area of senselessness. What I suggested is that we not switch to hypoxic diluents unless we need them and then further suggested that we don't need them as shallow as some think. I fence off my max depth for normoxic diluents when I reach 1.8 PP02 on the bottom, and run 20% dils to the associated depths for that. After that we switch to hypoxic dils. And it's darned rare for us to be in the depth band where we exceed setpoint PP02 with 20% and have not yet switched to hypoxic dils. Like 1 in 100 dives...... 2.5? 4.0? Nobody ever said that was appropriate. Maybe you got bored and skipped over the technical parts in the earlier series.... and the KISS has a valve on the 02 bottle for a reason...... And the title of the thread is wrong: NOBODY INCLUDING ME HAS PROPOSED THE DELIBERATE USE OF HOT DILUENTS. Can I make it any clearer than that? All I have EVER said is that we should not use hypoxic diluents unless required as they: (1) disallow us certain important SCC bailout modes, (2) hurt our deco possibilities using our dil open circuit, (3) have hypoxia/drowning potential if an ADV fails open or we get unwanted diluent into the loop near the surface (and read the current Inspiration thread on that issue it's a REAL one...). And no joke: With the reports of undesired diluent freeflows into the loop, this could KILL YOU RIGHT NOW! GUYS: If you get an ADV freeflow, (which is far more common than many other "silly bordering on insane" hypotheticals than people propose here,) you're not gonna tolerate 10% diluent in your loop on the surface for more than a few moments before doing the dead-fly routine just moments before you drown after your DSV slips from your unconcious mouth and you loose all of that nice bouyancy in the loop as it floods in about 5 seconds... Trust me on this, please?? as I've seen it for real (except we dived in and saved his sorry butt and now he buys me beer and mixes his 20% diluent with a smile) etc. I also mentioned that I will TOLERATE (not "desire") diluent that is SLIGHTLY hotter than my desired setpoint for a certain small fraction of my dives before I switch to hypoxic diluents for the aformentioned reasons, as I will reduce the PP02 by normal metabolism LONG BEFORE THE CNS CLOCK does jack-shi@ to me. I personally use 1.8 as my cut-off, feel free to use 1.6 or 1.4, whatever runs your CNS clock.... Get it? Dave __________________ www.southwestmafia.com "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
(Offline)

29th January 2007, 12:49	#12 (permalink)
Dave Sutton Membership Cancelled Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,637	Re: Use of 'hot' diluents Quote: (Originally Posted by chunter) As to the ADV...it's pretty easy to turn off a diluent valve or have a shut-off to prevent going hypoxic If you catch it in time... which is not something I would count on. Mere moments at low PP02 is deadly. Long time base on high PP02 is not deadly. I don't see any controversy when selecting between something that will kill me in seconds versus somethign that may cause distress aftr many minutes, that's all. Didn't mean to offend, just that many have not distinguished between accepting perhaps 1.6 as a diluent PP02 on the bottom and doing silly things like using a diluent with a 4.0 PP02 on the bottom. Lack of discrimination of the fine points has been a frustrating experience when trying to explain this system. Did not mean to be snide, just frustrated that some readers (nbot you, obviously) have a hard time dealing with grey areas and the variou shades of grey. Kind regards to all, Dave
(Offline)

29th January 2007, 12:54	#13 (permalink)
Dave Sutton Membership Cancelled Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,637	Re: Use of 'hot' diluents Quote: (Originally Posted by Mdemon) Makes sense to me. Additionally, you're not loading yourself with helium as much which will have an impact on your deco too. Maybe you should summarise this into a short article Dave? Would save repetitive threads? Would be pleased to write an article if the community desires. I can argue the diluent selection matrix from either side, and would be pleased to do so for the edification of all. I'd need to write about SCC bailout modes, VSC bailout modes, and constant bouyancy PP02 control modes too.. as carriage of 02 mixed with diluent gas opens up a lot more doors in the success matrix. Full discussion might tend towards book form, actually... The helium loading issue is really that of the use of the old "Scamahorn Slide" concepth (thanks to Leon for lending his name), meaning that for the first few minutes after bottoming you are a little hot, meaning that you have less inert gas loading, and then it slides towards more inert and less 02 as you burn te 02 out of the loop. There is a definate deco advantage. The old ZPlan had the option to use a slide for deco, and I take advantage of this using real-time measurement deco calc from my VR-3. The deco advantage can be significant. Dave
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29th January 2007, 14:51	#14 (permalink)
Padowan Proper Boffin Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Kent, UK. Posts: 518	Re: Use of 'hot' diluents I guess that another nice benefit of a slightly hotter dil is that once you reach your target depth, with a nice high PPO2, you've validated that your cells are capable of showing a PPO2 higher than (most average) SP. Having done some simulations with regards to depth, dil FO2 and SCR breath cycle modes, a higher FO2 dil will give a considerably extended SCR duration stabilising (at constant depth) at a much more deco beneficial (or perhaps more accurately a less deco loading) level. __________________ Padowan The future's bright, the future's Yellow .....for now padowan.net - Latest Video: Scapa Flow Rebreather Diving
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31st January 2007, 15:54	#15 (permalink)
jmhardingjr Son of a Sailor Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Sep 2005 Location: . . . this one particular harbor . . . Posts: 196	Re: Use of 'hot' diluents Dave, I'd love to see an article on this method. I heartily second the motion. Hell, write a book, I'll buy it. Cheers, Jay __________________ ". . . the sea's in my veins, my tradition remains, I'm just glad I don't live in a trailer . . ."
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