co2 monitoring

HBRB Bob · 5th February 2006, 01:08

I'd like to know

if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention

), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other.
Thanks Bob

abowie · 5th February 2006, 01:20

Personally I'd like it in mmHg because that's what I use at work every day.

Otherwise I don't think it matters, as long as there's a big noisy alarm and flashing lights when it reaches the "too high" level.

There's no reason you couldn't set it up so it could switch from one to the other. Anaesthetic machines usually offer either mmHg or percent CO2 depending on the anaesthetist's preference.

Gilles · 5th February 2006, 01:22

Bob;

I understand that the physiological impact of CO2 is due to the partial pressure rather than just the volume fraction. Hence ppCO2 needs to be known.

Given that ppCO2 needs to change so little to become dangerous also suggests the need need for very accurate measurement/monitoring. Hence sufficient accuracy to make a ppm measurement viable.

I would suggest a system capable of measuring ppm's but with ppCO2 interface for the human. Hope this helps.

E-man · 5th February 2006, 01:23

I wouldn't think it would matter as it should be 0 the whole time...if not a reaction is required by you

abowie · 5th February 2006, 03:55

Quote: (Originally Posted by sabgia)

Bob;

I understand that the physiological impact of CO2 is due to the partial pressure rather than just the volume fraction. Hence ppCO2 needs to be known.

Well yes...and no.

As long as a percentage is appropriately corrected back to 1ATM for whatever depth you are at (which is part of the definition for scrubber breakthrough) it doesn't really matter.

Personally I'd avoid ppm as it's not a common choice for CO2 monitoring in human physiology, and will be a biggish number (0.5% is 5000ppm), requiring 4 digits on the display.

Personally (others might disagree) I'd probably avoid numbers entirely as well, and just have simple binary "OK" or "NOT OK" setting.

My thinking behind this is that really all you want to know is whether your scrubber is working, or if it's not. Knowing how badly it's not working doesn't help you much as the solution is the same; go off the loop. So alarms go off when CO2 in the inspired limb reaches a certain level predetermined level (say 0.5%/7.5mmHg or whatever).

This would be simpler in terms of hardware and less (unnecessary) information for the diver to deal with.

The only possible benefit I can think of at the moment for a numerical display is that it might provide some useful information about dynamic scrubber breakthrough, in that you would be able to work out just how hard you can push the scrubber with exercise before it fails, but would you really want to do this?

AD_ward9 · 5th February 2006, 07:44

Quote: (Originally Posted by HBRB Bob)

I'd like to know

if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention

), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other.
Thanks Bob

We use a Blue LED for PPCO2.

The range of values is so huge, we show the Log of the value. Makes for a simple code. We use PPCO2 / 100. 0.0001 and up is one flash, 0.001 is two flashes, 0.01 is three, 0.1 is four and above 0.5 is continuous faster flashing.

We also use a silent mode, where it stays off unless there is a problem. Otherwise one ends with disco lights in front, and Blue interfers with underwater vision. Same for Green. In this mode, hit the handset button and it will show the code.

We also blank the PPO2 HUD LED when showing the PPCO2 level, as otherwise it is hard to focus on two lights flashing at once.

Cheers
Alex

jknights · 5th February 2006, 11:58

Quote: (Originally Posted by HBRB Bob)

I'd like to know

if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention

), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other.
Thanks Bob

I think that I would want it customisable (just like metres v feet on a dive computer, its the same value just displayed in different units).
That said I prefer %age but 0-full scale is very small so it will ve a strange range.

However I would want an alarm that was customisable as well. Since unbreathed air levels are 0.03% I would want it to have a variable setting in 0.1% increments between 0.1% to 6%, presuming CO2 toxicity effects start to strike at >6%. (Shortness of breath, etc.)

I can't find a definitive %age for the CO2 levels.
Also it seems that unacceptable levels in diving is >1.5%.
It seems to be somewhere between 2-9% all the different effects occur, depending on sources that I read.

Can anyone provide definitive values in % or references.

sven · 5th February 2006, 13:03

Quote: (Originally Posted by jknights)

Can anyone provide definitive values in % or references.

If I may hazard a guess, you will find that %CO2 (or fCO2) does not matter, but ppCO2 is more relevant (as it changes with depth).

E-man · 5th February 2006, 15:45

I think it would be more interesting to have 2 CO2 monitors one behind the scrubber and one after. The one behind measures actual CO2 produced and compares to a database of scrubber data provides a more accurate estimate of scrubber life remaining, while the monitor after the scrubber lets you know of a problem.

***caveseeker7*** · 5th February 2006, 19:02

I'd go with ppCO2 in ata SEV as most CCR divers are familiar with it.
% rather than ppm due to amount of numbers, mmHg doesn't mean anything to me.

O.5 ata SEV is the limit generally tested for, so that should be the high alarm I guess. But I would want to know of any CO2 in my gas passing through the scrubber.

5th February 2006, 01:08	#1 (permalink)
HBRB Bob New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Dec 2005 Location: Washington State USA Posts: 5	co2 monitoring I'd like to know if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other. Thanks Bob
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5th February 2006, 01:20	#2 (permalink)
abowie Fighting Girl Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: May 2005 Location: Land of Oz Posts: 574	Re: co2 monitoring Personally I'd like it in mmHg because that's what I use at work every day. Otherwise I don't think it matters, as long as there's a big noisy alarm and flashing lights when it reaches the "too high" level. There's no reason you couldn't set it up so it could switch from one to the other. Anaesthetic machines usually offer either mmHg or percent CO2 depending on the anaesthetist's preference. __________________ Andrew Bowie Rebreather-friendly Buddy
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5th February 2006, 01:22	#3 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 762	Re: co2 monitoring Bob; I understand that the physiological impact of CO2 is due to the partial pressure rather than just the volume fraction. Hence ppCO2 needs to be known. Given that ppCO2 needs to change so little to become dangerous also suggests the need need for very accurate measurement/monitoring. Hence sufficient accuracy to make a ppm measurement viable. I would suggest a system capable of measuring ppm's but with ppCO2 interface for the human. Hope this helps. __________________ Gilles http://www.dirrebreather.com
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5th February 2006, 01:23	#4 (permalink)
E-man On the loop! Current Rebreather/s: Inspiration Classic Optima Other Rebreather/s: Titan Join Date: Sep 2005 Location: Eastern Coast ;) Posts: 212	Re: co2 monitoring I wouldn't think it would matter as it should be 0 the whole time...if not a reaction is required by you
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5th February 2006, 03:55	#5 (permalink)
abowie Fighting Girl Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: May 2005 Location: Land of Oz Posts: 574	Re: co2 monitoring Quote: (Originally Posted by sabgia) Bob; I understand that the physiological impact of CO2 is due to the partial pressure rather than just the volume fraction. Hence ppCO2 needs to be known. Well yes...and no. As long as a percentage is appropriately corrected back to 1ATM for whatever depth you are at (which is part of the definition for scrubber breakthrough) it doesn't really matter. Personally I'd avoid ppm as it's not a common choice for CO2 monitoring in human physiology, and will be a biggish number (0.5% is 5000ppm), requiring 4 digits on the display. Personally (others might disagree) I'd probably avoid numbers entirely as well, and just have simple binary "OK" or "NOT OK" setting. My thinking behind this is that really all you want to know is whether your scrubber is working, or if it's not. Knowing how badly it's not working doesn't help you much as the solution is the same; go off the loop. So alarms go off when CO2 in the inspired limb reaches a certain level predetermined level (say 0.5%/7.5mmHg or whatever). This would be simpler in terms of hardware and less (unnecessary) information for the diver to deal with. The only possible benefit I can think of at the moment for a numerical display is that it might provide some useful information about dynamic scrubber breakthrough, in that you would be able to work out just how hard you can push the scrubber with exercise before it fails, but would you really want to do this? __________________ Andrew Bowie Rebreather-friendly Buddy
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5th February 2006, 07:44	#6 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,856	Re: co2 monitoring Quote: (Originally Posted by HBRB Bob) I'd like to know if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other. Thanks Bob We use a Blue LED for PPCO2. The range of values is so huge, we show the Log of the value. Makes for a simple code. We use PPCO2 / 100. 0.0001 and up is one flash, 0.001 is two flashes, 0.01 is three, 0.1 is four and above 0.5 is continuous faster flashing. We also use a silent mode, where it stays off unless there is a problem. Otherwise one ends with disco lights in front, and Blue interfers with underwater vision. Same for Green. In this mode, hit the handset button and it will show the code. We also blank the PPO2 HUD LED when showing the PPCO2 level, as otherwise it is hard to focus on two lights flashing at once. Cheers Alex Last edited by AD_ward9 : 5th February 2006 at 07:47. Reason: Typos
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5th February 2006, 11:58	#7 (permalink)
jknights New Member Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Other CCR Join Date: May 2005 Location: Oliva, Valencia, Spain. Posts: 121	Re: co2 monitoring Quote: (Originally Posted by HBRB Bob) I'd like to know if you had a co2 monitor ( electronic ) that you could use like a PPO2 monitor ( display on the wrist, mabe even a HUD too, Flashing red lights to make you pay attention), would you rather the display told you PPM ( parts per million) or read out in % CO2. Just a matter of what most Rebreather'ers would rather deal with. Also please state why you'ld prefer one to the other. Thanks Bob I think that I would want it customisable (just like metres v feet on a dive computer, its the same value just displayed in different units). That said I prefer %age but 0-full scale is very small so it will ve a strange range. However I would want an alarm that was customisable as well. Since unbreathed air levels are 0.03% I would want it to have a variable setting in 0.1% increments between 0.1% to 6%, presuming CO2 toxicity effects start to strike at >6%. (Shortness of breath, etc.) I can't find a definitive %age for the CO2 levels. Also it seems that unacceptable levels in diving is >1.5%. It seems to be somewhere between 2-9% all the different effects occur, depending on sources that I read. Can anyone provide definitive values in % or references. Last edited by jknights : 5th February 2006 at 12:08.
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5th February 2006, 13:03	#8 (permalink)
sven Blogs Admin / Forum Mod Current Rebreather/s: Inspiration Classic Other Rebreather/s: Evolution Join Date: Nov 2005 Location: Sydney Posts: 574	Re: co2 monitoring Quote: (Originally Posted by jknights) Can anyone provide definitive values in % or references. If I may hazard a guess, you will find that %CO2 (or fCO2) does not matter, but ppCO2 is more relevant (as it changes with depth). __________________ Regards, Sven [SIZE=1]The Sydney Project website: [URL]http://www.sydneyproject.com[/URL] My Blog: [URL]http://sven.rebreatherworld.com[/URL] "Whenever you find yourself on the side of the majority, it's time to pause and reflect." Mark Twain[/SIZE]
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5th February 2006, 15:45	#9 (permalink)
E-man On the loop! Current Rebreather/s: Inspiration Classic Optima Other Rebreather/s: Titan Join Date: Sep 2005 Location: Eastern Coast ;) Posts: 212	Re: co2 monitoring I think it would be more interesting to have 2 CO2 monitors one behind the scrubber and one after. The one behind measures actual CO2 produced and compares to a database of scrubber data provides a more accurate estimate of scrubber life remaining, while the monitor after the scrubber lets you know of a problem.
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5th February 2006, 19:02	#10 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,498	Re: co2 monitoring I'd go with ppCO2 in ata SEV as most CCR divers are familiar with it. % rather than ppm due to amount of numbers, mmHg doesn't mean anything to me. O.5 ata SEV is the limit generally tested for, so that should be the high alarm I guess. But I would want to know of any CO2 in my gas passing through the scrubber. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
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