Functionaing with only 92% O2

IDS_Bill · 9th October 2007, 20:43

Quote: (Originally Posted by diverreb)

When you calibrate for O2 on the surface it's going to read the 92% as 100% or 1.0. That isn't adjustable.

So then what do you do? Assume that if you set the unit to run at 1.3 that it's really running at 1.2?

Then it's also calculating Deco at 1.3, not 1.2. If your doing multi day dives and a few dives a day that deco error will be cumulative.

Do you have an independent computer (not hooked into a cell) you can run at 1.2 as an option?

Just my thoughts here, but I'd be a little concerned about running with 92% for a weeks worth of dives.

Richie

I will have my Nitek He as a backup. I am seriously considering getting a VR3 and sensor for a backup. That would ease this.

Bill

JS1scuba · 9th October 2007, 20:59

PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant.

Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%.

If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule.

Cheers

diverreb · 9th October 2007, 22:31

Quote: (Originally Posted by JS1scuba)

PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant.

Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%.

If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule.

Cheers

On dives of 130' or less we typically dive the O2ptima's at a .7 for the most part until we get to a reasonable depth then we switch to the dive set point. Some of the guys wait until they reach bottom before switching to their dive set point. Also in this scenario the unit thinks it's at 1.3 when it's actually at 1.2 as it was calibrated to 100% when it is really 92%.

As far as deco time. I figured that was the case as far as one dive was concerned, but how about three or four dives a day for a weeks worth of diving, like they do on a live-aboard or dive vacation weeks. It might be a bit more significant by weeks end.

Richie

Simon A · 9th October 2007, 23:01

If you have to you can work out corrected PPO2's and use the hammerhead as a bottom timer with tables. But why calibrate the optima on the 92% at all? calibrate it on 100% at home, then using an o2 analyser to check what gases you are using (you do analyse your O2 and Dil don't you?) just check the hammerhead calibration is still correct against your 2 known gases before every dive, you only need to run calibration if it doesn't agree with the analyser.
HTH
Simon A

Mixaddict · 10th October 2007, 06:24

I did a week on my inspo on the Oddyssey a couple of years ago. I was getting about 94%. Did the entire week without any side effects. Obviously, I'm not suggesting that it will work for you, but I just adjusted my inspo to match what my gas analysis gave me. I don't know if that was the right thing to do or not, but it worked for me. The biggest issue for me, was that I tend to get narked a little easier on CCR than I do on OC. (Don't reall know why, but I suspect it has to do with the task loading.) Unfortunately, they don't have any helium on the boat when you are doing the really deep stuff like the San Fransisco Maru etc.

Mark Chase · 10th October 2007, 08:25

Quote: (Originally Posted by IDS_Bill)

Hey everyone,

I am taking off in April to hit the Truk Odyssey for a week for my 40th and they said they only have 92% O2. I am trying to figure out whether I should take my CCR or not. This trip is really why I originally bought and trained on the unit.

Does anyone have any data on how to adjust to the lower percentage safely? Can you calibrate under pressure or modify the Hammerhead settings somehow?

Thanks,

Bill

Calibrate the Hammer Head before you go out then do the weeks diving??? the cells are not going to degrade significantly in a week or even a fortnight. If you have a cell failure then i can see a problem but apart from that why on earth would you want to calibrate again?

Check with KJ but I was told the units do not lose their calibration settings when you take the batteries out.

When I used my HH i did the 02 flush then checked the readings. Using 91% id expect to see 0.21 in air and 0.90 ish when triple flushed with 02. If i did i
wouldn't bother calibrating again.

If i were multi day diving and I did an 02 flush and only got say 0.85 on my 92% my first suspicion would be moisture on the cell faces not a calibration issue. If My unit calibrated fin three days ago and suddenly one cell is reading.75 and the other two 0.90 id suspect a wiring or cell error not a calibration issue.

ATB

Mark

diverreb · 10th October 2007, 13:00

I didn't think about the pre calibration idea. That sounds like a reasonable thing to do & as long as it checks out, as Mark mentioned, reading 92 or so, it should work.

I know my unit does keep the calibration when the batteries are changed or taken out for a week, but for a trip like this people seem to use Safts and they seem to last for the week, or with just one change during the week.

My handsets keep an initial 1.0 calibration between .97 and 1.02 over a two week period when the unit hasn't been used. Not a critical difference.

Does this mean that yours will do the same? That's your call.

Richie

Yankee Rebel · 12th October 2007, 06:15

can a person carry on a small medical O2 cylinder on a flight? take med O2 from home.. and have a known O2 to calibrate with while on vacation? complete with a note from your Doctor as to the medical necessity that you have your O2 with you at all times in case you suffer from an attack of Asthma or something that youre prone to, that causes you to have an unsafe O2 content in your blood stream?
or is that more a PITA than its worth?

maybe calibrate at a vets office or somewhere friendly that might have 100% O2? local medical facilities may suffer the same O2 source/availability though.

what about a RX for med O2 and throw a small Med bottle in your luggage.. get it filled when you get off the plain, and have a known O2? again potential to suffer supply issues.

just thinking out loud. dont know nuff bout them fancy computers to have any input there.

can you just use the air around you to calibrate your O2 cells with? then cross check it to the O2 that youre getting on site and another persons readings on the O2%?

Gilles · 12th October 2007, 23:39

Quote: (Originally Posted by paulraymaekers)

just calibrate correctly
paul

That is key

Quote: (Originally Posted by Simon A)

calibrate it on 100% at home, then using an o2 analyser to check what gases you are using (you do analyse your O2 and Dil don't you?) just check the hammerhead calibration is still correct against your 2 known gases before every dive, you only need to run calibration if it doesn't agree with the analyser.
HTH
Simon A

This works in practise

, providing you don't lose a cell and need to change. Your holiday is jeopardised by not being able to set your cal-gas purity.

Quote: (Originally Posted by Yankee Rebel)

can you just use the air around you to calibrate your O2 cells with? then cross check it to the O2 that youre getting on site and another persons readings on the O2%?

Not without putting your life in grave jeopardy. If your cells become worn, they will tend to output less mV than needed to provide you a correct PO2 readout.

If it's do-able, bringing your own supply of cal-gas may be your only option for mitigating against the need for a re-calibration.

Good luck

Mark Chase · 13th October 2007, 03:47

Quote: (Originally Posted by JS1scuba)

PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant.

Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%.

If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule.

Cheers

Is my conversion wrong?? I thaught 46 FSW was 46 feet deep? thats 14m so 92% would be max 2.2pp02 I think

with 92% you should hit 1.3 at 4m so about 13fsw

Also i note a few comments about being concerned about running the units on 92% for a week?

Why is this a concern?

If depth / narcosis isnt an issue surley you could run the unit off just about any Nitrox mix above say 50%

I strugle to see a problem on a ECCR except for the solinoid being worked harder and needing to drop to a low set point for shalow deco.

ATB

Mark

9th October 2007, 20:43	#11 (permalink)
IDS_Bill New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Aug 2005 Location: Arizona, USA Posts: 22	Re: Functionaing with only 92% O2 Quote: (Originally Posted by diverreb) When you calibrate for O2 on the surface it's going to read the 92% as 100% or 1.0. That isn't adjustable. So then what do you do? Assume that if you set the unit to run at 1.3 that it's really running at 1.2? Then it's also calculating Deco at 1.3, not 1.2. If your doing multi day dives and a few dives a day that deco error will be cumulative. Do you have an independent computer (not hooked into a cell) you can run at 1.2 as an option? Just my thoughts here, but I'd be a little concerned about running with 92% for a weeks worth of dives. Richie I will have my Nitek He as a backup. I am seriously considering getting a VR3 and sensor for a backup. That would ease this. Bill
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9th October 2007, 20:59	#12 (permalink)
JS1scuba RebreatherWorld Sponsor Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Sport Kiss Classic Kiss MK 15.X Join Date: Oct 2005 Location: Lake Havasu City, AZ - USA Posts: 511	Re: Functionaing with only 92% O2 PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant. Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%. If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule. Cheers __________________ Joel Silverstein, VP COO Tech Diving Limited a Division of Scuba Training and Technology Inc. http://www.nautilusdiveplanner.com http://www.nobubblediving.com
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9th October 2007, 22:31	#13 (permalink)
diverreb DE/MD/NJ Wreck Diver Current Rebreather/s: Optima Other Rebreather/s: Join Date: Mar 2007 Location: Dover, DE Posts: 595	Re: Functionaing with only 92% O2 Quote: (Originally Posted by JS1scuba) PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant. Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%. If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule. Cheers On dives of 130' or less we typically dive the O2ptima's at a .7 for the most part until we get to a reasonable depth then we switch to the dive set point. Some of the guys wait until they reach bottom before switching to their dive set point. Also in this scenario the unit thinks it's at 1.3 when it's actually at 1.2 as it was calibrated to 100% when it is really 92%. As far as deco time. I figured that was the case as far as one dive was concerned, but how about three or four dives a day for a weeks worth of diving, like they do on a live-aboard or dive vacation weeks. It might be a bit more significant by weeks end. Richie
(Offline)

9th October 2007, 23:01	#14 (permalink)
Simon A Escapee from DIY Rebreather's Current Rebreather/s: Inspiration Classic Other Rebreather/s: Not Bought Yet Join Date: Feb 2005 Location: Reading, UK Posts: 312	Re: Functioning with only 92% O2 If you have to you can work out corrected PPO2's and use the hammerhead as a bottom timer with tables. But why calibrate the optima on the 92% at all? calibrate it on 100% at home, then using an o2 analyser to check what gases you are using (you do analyse your O2 and Dil don't you?) just check the hammerhead calibration is still correct against your 2 known gases before every dive, you only need to run calibration if it doesn't agree with the analyser. HTH Simon A
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10th October 2007, 06:24	#15 (permalink)
Mixaddict Always Learning! Current Rebreather/s: Inspiration Vision Evolution Other CCR Dolphin Other Rebreather/s: Inspiration Classic Other CCR Dolphin Join Date: Jan 2006 Location: Draper, Utah USA Posts: 476	Re: Functionaing with only 92% O2 I did a week on my inspo on the Oddyssey a couple of years ago. I was getting about 94%. Did the entire week without any side effects. Obviously, I'm not suggesting that it will work for you, but I just adjusted my inspo to match what my gas analysis gave me. I don't know if that was the right thing to do or not, but it worked for me. The biggest issue for me, was that I tend to get narked a little easier on CCR than I do on OC. (Don't reall know why, but I suspect it has to do with the task loading.) Unfortunately, they don't have any helium on the boat when you are doing the really deep stuff like the San Fransisco Maru etc. __________________ Randy Thornton (MixAddict) Inspiration, Evolution,Hammerhead & Sentinel CCR Instructor
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10th October 2007, 08:25	#16 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,697	Re: Functionaing with only 92% O2 Quote: (Originally Posted by IDS_Bill) Hey everyone, I am taking off in April to hit the Truk Odyssey for a week for my 40th and they said they only have 92% O2. I am trying to figure out whether I should take my CCR or not. This trip is really why I originally bought and trained on the unit. Does anyone have any data on how to adjust to the lower percentage safely? Can you calibrate under pressure or modify the Hammerhead settings somehow? Thanks, Bill Calibrate the Hammer Head before you go out then do the weeks diving??? the cells are not going to degrade significantly in a week or even a fortnight. If you have a cell failure then i can see a problem but apart from that why on earth would you want to calibrate again? Check with KJ but I was told the units do not lose their calibration settings when you take the batteries out. When I used my HH i did the 02 flush then checked the readings. Using 91% id expect to see 0.21 in air and 0.90 ish when triple flushed with 02. If i did i wouldn't bother calibrating again. If i were multi day diving and I did an 02 flush and only got say 0.85 on my 92% my first suspicion would be moisture on the cell faces not a calibration issue. If My unit calibrated fin three days ago and suddenly one cell is reading.75 and the other two 0.90 id suspect a wiring or cell error not a calibration issue. ATB Mark __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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10th October 2007, 13:00	#17 (permalink)
diverreb DE/MD/NJ Wreck Diver Current Rebreather/s: Optima Other Rebreather/s: Join Date: Mar 2007 Location: Dover, DE Posts: 595	Re: Functionaing with only 92% O2 I didn't think about the pre calibration idea. That sounds like a reasonable thing to do & as long as it checks out, as Mark mentioned, reading 92 or so, it should work. I know my unit does keep the calibration when the batteries are changed or taken out for a week, but for a trip like this people seem to use Safts and they seem to last for the week, or with just one change during the week. My handsets keep an initial 1.0 calibration between .97 and 1.02 over a two week period when the unit hasn't been used. Not a critical difference. Does this mean that yours will do the same? That's your call. Richie
(Offline)

12th October 2007, 06:15	#18 (permalink)
Yankee Rebel Custom Title Allowed! Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Jan 2006 Location: California Posts: 147	Re: Functionaing with only 92% O2 can a person carry on a small medical O2 cylinder on a flight? take med O2 from home.. and have a known O2 to calibrate with while on vacation? complete with a note from your Doctor as to the medical necessity that you have your O2 with you at all times in case you suffer from an attack of Asthma or something that youre prone to, that causes you to have an unsafe O2 content in your blood stream? or is that more a PITA than its worth? maybe calibrate at a vets office or somewhere friendly that might have 100% O2? local medical facilities may suffer the same O2 source/availability though. what about a RX for med O2 and throw a small Med bottle in your luggage.. get it filled when you get off the plain, and have a known O2? again potential to suffer supply issues. just thinking out loud. dont know nuff bout them fancy computers to have any input there. can you just use the air around you to calibrate your O2 cells with? then cross check it to the O2 that youre getting on site and another persons readings on the O2%?
(Offline)

12th October 2007, 23:39	#19 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 762	Re: Functionaing with only 92% O2 Quote: (Originally Posted by paulraymaekers) just calibrate correctly paul That is key Quote: (Originally Posted by Simon A) calibrate it on 100% at home, then using an o2 analyser to check what gases you are using (you do analyse your O2 and Dil don't you?) just check the hammerhead calibration is still correct against your 2 known gases before every dive, you only need to run calibration if it doesn't agree with the analyser. HTH Simon A This works in practise , providing you don't lose a cell and need to change. Your holiday is jeopardised by not being able to set your cal-gas purity. Quote: (Originally Posted by Yankee Rebel) can you just use the air around you to calibrate your O2 cells with? then cross check it to the O2 that youre getting on site and another persons readings on the O2%? Not without putting your life in grave jeopardy. If your cells become worn, they will tend to output less mV than needed to provide you a correct PO2 readout. If it's do-able, bringing your own supply of cal-gas may be your only option for mitigating against the need for a re-calibration. Good luck __________________ Gilles http://www.dirrebreather.com
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13th October 2007, 03:47	#20 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,697	Re: Functionaing with only 92% O2 Quote: (Originally Posted by JS1scuba) PO2 is PO2. With 92% ean you will not be able to get a 1.3 set point until about 46 fsw. So you may want to fly the unit at a set point of 1.1 or 1.2. I suspect you will be using Air as the diluent there so the nitrogen that is in the "oxygen" is insignificant. Many PSA - Pressure Swing Adsorption oxygen generators can only produce up to 95% oxygen (balance inert) some as low as 88%. If you ran a profile using EAN 92 and Air as a dill and 100% and Air as dill you will see there is virtually no difference in the decompression schedule. Cheers Is my conversion wrong?? I thaught 46 FSW was 46 feet deep? thats 14m so 92% would be max 2.2pp02 I think with 92% you should hit 1.3 at 4m so about 13fsw Also i note a few comments about being concerned about running the units on 92% for a week? Why is this a concern? If depth / narcosis isnt an issue surley you could run the unit off just about any Nitrox mix above say 50% I strugle to see a problem on a ECCR except for the solinoid being worked harder and needing to drop to a low set point for shalow deco. ATB Mark __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

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