CO2 monitoring?

jiseson · 29th October 2006, 12:21

After reading an article by Bruce Wienke I see that our bodies are incredibly sensitive to the slightest of changes to CO2 to almost every area of issues re. to diving gas pressure issues. Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you? Am I missing something? Have them in my house-cost $20!

***diverklondike*** · 29th October 2006, 13:07

Quote: (Originally Posted by jiseson)

After reading an article by Bruce Wienke I see that our bodies are incredibly sensitive to the slightest of changes to CO2 to almost every area of issues re. to diving gas pressure issues. Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you? Am I missing something? Have them in my house-cost $20!

I think you will find quite a few threads on Rebreather World that cover the topic and the reasons quite well. A quick search of CO2, CO2 monitoring etc will do the trick...

Dive Safe...

Mark

Dutchy · 29th October 2006, 16:39

Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction.
If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt

and was a magnitude more expensive)

Faceless · 29th October 2006, 16:48

You absolutety right regarding nesssity of CO2 monitoring.
Hovewer, CO2 monitor suitable to work in Rebreather shall meet much more hard criterias, than standard 20$ ones used in-house.
They include:
work in 100% humidity, ability to continie work after loop being flooded and flushed, ability to work under diffirent ambient temperatures depending on conditions of dive (from 1-2 to 40 Celcius), tolerate full range of ambient pressures, in range from 1 to 20 ATM (at least for sport diving), low power consumption ( we cannot take a power station to underwater

)

And don't forget reliability of course, i.e. sensor MTBF (mean time between failures) must be within reasonable values, cause we're talking about life support system here, right ?

As i'm aware currently there are several companies working on such CO2 monitor.
For example Alex known as AD_ward9 on this board is going to present CO2 monitor & controller meeting these criterias at DEMA.

(Mumbling to myself) I wish I be there

UPD: and one more criteria: this CO2 monitor unlike those 20$ cheapos should be fast, i'e it must react on CO2 changes within the loop space in less than 2-3 minutes.

jiseson · 29th October 2006, 21:22

Quote: (Originally Posted by Dutchy)

Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction.
If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt

and was a magnitude more expensive)

u r right those are for CO not CO2 , but i still maintain it seams rather obvious that rebreathers are lacking this in concept-to me a fault

**Gill Envy** · 30th October 2006, 20:38

jonathan, as has been mentioned, there are quite a few threads on this. it sounds like there is at least one co2 monitor on the way. Oceanic claims their upcoming rebreather will have one.

it too was a mystery to me why there was not one on the market. I forget which thread it is that someone worked out the numbers on, but the amount of co2 necessary to tox you is tiney. On a deep dive the difference between detectible levels and unconsiousness is something like one half of one percent of the total gas fraction. Creating a reliable monitor that is that sensative and can handle the %100 relative humidity in the loop is quite a task it seems to me. I braught this argument up when i was still making my decition and someone pointed out to me that by the time there is detectible co2 in the loop it is pretty much too late. this person was very pro vision electronics and made a case for the monitoring of the sorb being of a higher priority since breakthrough is best prevented in the first place. I still think a co2 monitor would be cool, but not as useful as one might think. I'm curious to see when they do come out, just how reliable they turn out to be.

Dutchy · 30th October 2006, 20:52

Quote: (Originally Posted by jiseson)

... i still maintain it seams rather obvious that rebreathers are lacking this in concept-to me a fault

Agreed

iain-hsm · 31st October 2006, 09:49

Quote: (Originally Posted by Dutchy)

Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction.
If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt

Dutchy
This post can be summed up as all about the figure zero.
If you remove the zero from your 220 volt and add it to your $1000 dollar cost you will be about spot on the mark. Not only is there a need for C02 detection but there has been provision made in our EU directives for C02 detection since the beginning of the directive but was limited by the term if fitted thus making it an option for product designers to incorporate into there CE approved rebreathers.

Due to the relative high cost the option taken was not to bother. However as the reliability of the C02 sensor is critical and commercial gas detectors are not suitable for diving applications. This required a completely new development of sensor to accommodate pressure, temperature and humidity shortfalls of commercial dry gas C02 detectors.

Due to the high cost in producing a specific application detector and unlike the cheap disposable oxygen sensor technology we had to get away from the third cell forth cell, voting logic, balance and checks. The military were the most obvious choice for introduction due to the high specification required but the sport market has not been forgotten. Our first C02 detector was for the LARV oxygen rebreather and was shown at last years DEMA05 show to select parties. It was also discussed on the forum last year. I will have the latest sensor variant and boards at this year’s DEMA06 show again both a working unit and the housing and board options for those interested. The latest unit is for breath by breath detection of the inspired gas with an accuracy of +/- 0.2kPa or
0.2% at 1 bar. Sensor life is 12 years calibration is done annually (by the user) depth is 200MSW (660FSW). Battery is a Saft LSH14 3.6V battery life is 20 hours continuous use. Humidity is now
0-100% flooded condition.

In conclusion as the Saft battery is a nominal 3.6 volts and operates at approximately 3.4 volts but the sensor minimum voltage requirement is 1.5 volts. In keeping with the assumption that cost is relative to power then I assume we should reduce the sensor cost accordingly. Iain Middlebrook

divetheworld · 31st October 2006, 17:58

Sensors for this purpose are available from E2V. A company in the UK called Ingenion have develpoed a system for this purpose using those sensors, it works.
They use two sensors with different IR frequency detection and a compensation circuit which effects a smooth transition between them with respect to ambient pressure with compensation for temperature and humidity.

Can not tell you any more an this point.
Wait and see.

O.C.Diver · 31st October 2006, 18:38

Quote: (Originally Posted by jiseson)

Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you?

IMO, it would likely lead to more deaths. Just one more false security blanket for a new Rebreather diver trying to push the limit of a few dollars worth of kitty litter.

Ted

29th October 2006, 12:21	#1 (permalink)
jiseson DSIX/O2PTIMA Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jun 2006 Location: long island,ny Posts: 541	CO2 monitoring? After reading an article by Bruce Wienke I see that our bodies are incredibly sensitive to the slightest of changes to CO2 to almost every area of issues re. to diving gas pressure issues. Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you? Am I missing something? Have them in my house-cost $20! __________________ *Jonathan D Iseson*
(Offline)

29th October 2006, 13:07	#2 (permalink)
*diverklondike* Moderator Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Oct 2005 Location: Delaware, USA Posts: 1,557	Re: CO2 monitoring? Quote: (Originally Posted by jiseson) After reading an article by Bruce Wienke I see that our bodies are incredibly sensitive to the slightest of changes to CO2 to almost every area of issues re. to diving gas pressure issues. Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you? Am I missing something? Have them in my house-cost $20! I think you will find quite a few threads on Rebreather World that cover the topic and the reasons quite well. A quick search of CO2, CO2 monitoring etc will do the trick... Dive Safe... Mark
(Online)

29th October 2006, 16:39	#3 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 729	Re: CO2 monitoring? Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction. If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt and was a magnitude more expensive) __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
(Offline)

29th October 2006, 16:48	#4 (permalink)
Faceless alone lurking in wrecks Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: May 2006 Location: France, Montpellier Posts: 92	Re: CO2 monitoring? You absolutety right regarding nesssity of CO2 monitoring. Hovewer, CO2 monitor suitable to work in Rebreather shall meet much more hard criterias, than standard 20$ ones used in-house. They include: work in 100% humidity, ability to continie work after loop being flooded and flushed, ability to work under diffirent ambient temperatures depending on conditions of dive (from 1-2 to 40 Celcius), tolerate full range of ambient pressures, in range from 1 to 20 ATM (at least for sport diving), low power consumption ( we cannot take a power station to underwater ) And don't forget reliability of course, i.e. sensor MTBF (mean time between failures) must be within reasonable values, cause we're talking about life support system here, right ? As i'm aware currently there are several companies working on such CO2 monitor. For example Alex known as AD_ward9 on this board is going to present CO2 monitor & controller meeting these criterias at DEMA. (Mumbling to myself) I wish I be there UPD: and one more criteria: this CO2 monitor unlike those 20$ cheapos should be fast, i'e it must react on CO2 changes within the loop space in less than 2-3 minutes. Last edited by Faceless : 29th October 2006 at 17:08. Reason: damn typos, sorry for bad English
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29th October 2006, 21:22	#5 (permalink)
jiseson DSIX/O2PTIMA Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jun 2006 Location: long island,ny Posts: 541	Re: CO2 monitoring? Quote: (Originally Posted by Dutchy) Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction. If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt and was a magnitude more expensive) u r right those are for CO not CO2 , but i still maintain it seams rather obvious that rebreathers are lacking this in concept-to me a fault __________________ *Jonathan D Iseson*
(Offline)

30th October 2006, 20:38	#6 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,302	Re: CO2 monitoring? jonathan, as has been mentioned, there are quite a few threads on this. it sounds like there is at least one co2 monitor on the way. Oceanic claims their upcoming rebreather will have one. it too was a mystery to me why there was not one on the market. I forget which thread it is that someone worked out the numbers on, but the amount of co2 necessary to tox you is tiney. On a deep dive the difference between detectible levels and unconsiousness is something like one half of one percent of the total gas fraction. Creating a reliable monitor that is that sensative and can handle the %100 relative humidity in the loop is quite a task it seems to me. I braught this argument up when i was still making my decition and someone pointed out to me that by the time there is detectible co2 in the loop it is pretty much too late. this person was very pro vision electronics and made a case for the monitoring of the sorb being of a higher priority since breakthrough is best prevented in the first place. I still think a co2 monitor would be cool, but not as useful as one might think. I'm curious to see when they do come out, just how reliable they turn out to be. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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30th October 2006, 20:52	#7 (permalink)
Dutchy SK#007 Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: Apr 2006 Location: Nieuwegein (The Netherlands) Posts: 729	Re: CO2 monitoring? Quote: (Originally Posted by jiseson) ... i still maintain it seams rather obvious that rebreathers are lacking this in concept-to me a fault Agreed __________________ = This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007
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31st October 2006, 09:49	#8 (permalink)
iain-hsm Custom Title Allowed! Current Rebreather/s: MK 15.X Other CCR Other SCR Other Rebreather/s: Other CCR Other SCR Join Date: Mar 2005 Location: Loughborough England uk Posts: 347	Re: CO2 monitoring? Quote: (Originally Posted by Dutchy) Can you send me a few at that price? Nah seriously check again. These sensors will detect carbonMOnoxide. (CO). Carbon monoxide is easily detctable using a series of reagens. carbonDIoxide is related but doesn't react as well. In general CO is a result of a bad reaction (e.g fire with not enough air (or more precise oxygen) ) whereas carbondioxide is the result of a complete and good fire/reaction. If anyone produces a reliable device for under $1000 fit for use in our humid/condensing conditions then he'll have to be prepared for thousand of orders both for commercial diving and recreational purposes alike. The closest I've seen is bulky and still needs 220 volt Dutchy This post can be summed up as all about the figure zero. If you remove the zero from your 220 volt and add it to your $1000 dollar cost you will be about spot on the mark. Not only is there a need for C02 detection but there has been provision made in our EU directives for C02 detection since the beginning of the directive but was limited by the term if fitted thus making it an option for product designers to incorporate into there CE approved rebreathers. Due to the relative high cost the option taken was not to bother. However as the reliability of the C02 sensor is critical and commercial gas detectors are not suitable for diving applications. This required a completely new development of sensor to accommodate pressure, temperature and humidity shortfalls of commercial dry gas C02 detectors. Due to the high cost in producing a specific application detector and unlike the cheap disposable oxygen sensor technology we had to get away from the third cell forth cell, voting logic, balance and checks. The military were the most obvious choice for introduction due to the high specification required but the sport market has not been forgotten. Our first C02 detector was for the LARV oxygen rebreather and was shown at last years DEMA05 show to select parties. It was also discussed on the forum last year. I will have the latest sensor variant and boards at this year’s DEMA06 show again both a working unit and the housing and board options for those interested. The latest unit is for breath by breath detection of the inspired gas with an accuracy of +/- 0.2kPa or 0.2% at 1 bar. Sensor life is 12 years calibration is done annually (by the user) depth is 200MSW (660FSW). Battery is a Saft LSH14 3.6V battery life is 20 hours continuous use. Humidity is now 0-100% flooded condition. In conclusion as the Saft battery is a nominal 3.6 volts and operates at approximately 3.4 volts but the sensor minimum voltage requirement is 1.5 volts. In keeping with the assumption that cost is relative to power then I assume we should reduce the sensor cost accordingly. Iain Middlebrook Last edited by schford : 31st October 2006 at 10:06. Reason: Format adjusted - SF fixed quote at top
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31st October 2006, 17:58	#9 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,560	Re: CO2 monitoring? Sensors for this purpose are available from E2V. A company in the UK called Ingenion have develpoed a system for this purpose using those sensors, it works. They use two sensors with different IR frequency detection and a compensation circuit which effects a smooth transition between them with respect to ambient pressure with compensation for temperature and humidity. Can not tell you any more an this point. Wait and see. __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. CHECK OUT OUR INTERWEBS FOR CUSTOM REBREATHER UPGRADES *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
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31st October 2006, 18:38	#10 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 213	Re: CO2 monitoring? Quote: (Originally Posted by jiseson) Why then does n't any of these rebreathers have a CO2 monitoring device- seems as important as the 02-it too can kill you? IMO, it would likely lead to more deaths. Just one more false security blanket for a new Rebreather diver trying to push the limit of a few dollars worth of kitty litter. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
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