Lower than expected pO2

**Steve** · 8th January 2006, 23:10

I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team?

Mike · 8th January 2006, 23:30

Was the O2 you calibrated with the same as you were using on the dive?

If not, check the O2% of your onboard O2 - I know that mine is only about 98% at the moment due to lack of discipline in flushing whips etc. If yours is actually down around 95% it will give the results you are seeing.

Otherwise, is there a depth difference between your pressure guage and your sensors (how long are your arms

)? Or were you fizzing like mad at the time?

Mike

sensor330 · 8th January 2006, 23:39

Quote: (Originally Posted by Steve)

I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team?

Was this your first dive of the day? I had something similar happen to me as well this weekend. I'm diving a YBOD with HH so the cal is similar. When I got to the surface I checked me cal and all my cells read .90. So I re-cal did another dive and everything checked out. Weird don't no why as I didn't do anything didn't than I normally do

mattmexico · 8th January 2006, 23:42

If not, check the O2% of your onboard O2 - I know that mine is only about 98% at the moment due to lack of discipline in flushing whips etc. If yours is actually down around 95% it will give the results you are seeing.

Yo there

I had some supplier problems at times when the O2 in the suplied gas company tank was well below 100 %. On a side note some years ago a couple of people died in a Mexican hospital because in the suplied hospital tanks was not 100 % O2 but CO2 and the hospitall staff did not analyze before they plummed it into the hospital O2 pipeline ....

Matt

***jradomski*** · 9th January 2006, 02:13

Quote: (Originally Posted by sensor330)

Was this your first dive of the day? I had something similar happen to me as well this weekend. I'm diving a YBOD with HH so the cal is similar. When I got to the surface I checked me cal and all my cells read .90. So I re-cal did another dive and everything checked out. Weird don't no why as I didn't do anything didn't than I normally do

A suggestion... after you do all your good flushes, get the mv reading,let the rig sit at least 10 minutes if 100% oxygen before calibrating.. then check the MV reading, if it droppped flush again, repeat until stable..

If readings dont stabilize, you either dont have 100% oxygen (in that case just do another sigle flush and calibrate, but know its going to be higher than actual loop), or you have flaky cells...

Drmike · 9th January 2006, 03:41

Quote: (Originally Posted by Steve)

I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team?

Your cells are probably current limited to 1.45 and need replacing.

**JPJones** · 9th January 2006, 12:40

Were you ever able to get a 1.6 reading at that depth? If your breathing hard and like most of us don't really have 100% and with the normal error rate of the sensors it would not be an unusual reading.

Sutty · 9th January 2006, 13:25

Quote: (Originally Posted by Steve)

I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team?

How about coming off the loop with readings of 1.45 and dropping a few metres - if PO2 doesn't rise the sensors must be current limited. Its an easy way to check the sensors can read higher than you are willing to breathe too.

***schford*** · 10th January 2006, 18:39

When you got out of the water did you pop the head out straight away and check for moisture on the cell faces?

I found that when I dive in warm water I get some moisture on the faces and on the final stop I notice some times it reads low - interestingly it never happens in cold water and does not happen to Sarah at all

Stuart

**UWSojourner** · 18th January 2006, 01:18

Are you using ISC or Shearwater electronics?

8th January 2006, 23:10	#1 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,070	Lower than expected pO2 I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team? __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
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8th January 2006, 23:30	#2 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 322	Re: Lower than expected pO2 Was the O2 you calibrated with the same as you were using on the dive? If not, check the O2% of your onboard O2 - I know that mine is only about 98% at the moment due to lack of discipline in flushing whips etc. If yours is actually down around 95% it will give the results you are seeing. Otherwise, is there a depth difference between your pressure guage and your sensors (how long are your arms )? Or were you fizzing like mad at the time? Mike __________________ Open ....... Closed Mind ........ Loop
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8th January 2006, 23:39	#3 (permalink)
sensor330 Custom Title Allowed! Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Join Date: Feb 2005 Location: Victoria, British Columbia, Canada Posts: 549	Re: Lower than expected pO2 Quote: (Originally Posted by Steve) I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team? Was this your first dive of the day? I had something similar happen to me as well this weekend. I'm diving a YBOD with HH so the cal is similar. When I got to the surface I checked me cal and all my cells read .90. So I re-cal did another dive and everything checked out. Weird don't no why as I didn't do anything didn't than I normally do
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8th January 2006, 23:42	#4 (permalink)
mattmexico Rebreather World Writer Current Rebreather/s: Megalodon Classic Kiss Optima RB80 / Clone Other Rebreather/s: Inspiration Classic Evolution Prism Topaz Sport Kiss RB80 / Clone Join Date: Aug 2005 Location: Mexico, Q.Roo, Playa del Carmen Posts: 752	Re: Lower than expected pO2 If not, check the O2% of your onboard O2 - I know that mine is only about 98% at the moment due to lack of discipline in flushing whips etc. If yours is actually down around 95% it will give the results you are seeing. Yo there I had some supplier problems at times when the O2 in the suplied gas company tank was well below 100 %. On a side note some years ago a couple of people died in a Mexican hospital because in the suplied hospital tanks was not 100 % O2 but CO2 and the hospitall staff did not analyze before they plummed it into the hospital O2 pipeline .... Matt __________________ N 20' 37.617' W 87' 04.693' www.andreaswmatthes.com
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9th January 2006, 02:13	#5 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,817	Re: Lower than expected pO2 Quote: (Originally Posted by sensor330) Was this your first dive of the day? I had something similar happen to me as well this weekend. I'm diving a YBOD with HH so the cal is similar. When I got to the surface I checked me cal and all my cells read .90. So I re-cal did another dive and everything checked out. Weird don't no why as I didn't do anything didn't than I normally do A suggestion... after you do all your good flushes, get the mv reading,let the rig sit at least 10 minutes if 100% oxygen before calibrating.. then check the MV reading, if it droppped flush again, repeat until stable.. If readings dont stabilize, you either dont have 100% oxygen (in that case just do another sigle flush and calibrate, but know its going to be higher than actual loop), or you have flaky cells... __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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9th January 2006, 03:41	#6 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,128	Re: Lower than expected pO2 Quote: (Originally Posted by Steve) I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team? Your cells are probably current limited to 1.45 and need replacing. __________________ Get a girlfriend you sad twat - a Rebreather is an unfaithful mistress - dont blind yourself to her faults just because she goes down on you
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9th January 2006, 12:40	#7 (permalink)
JPJones O2ptima Test Dummy Current Rebreather/s: Inspiration Classic Megalodon Sport Kiss Classic Kiss Optima Titan Other Rebreather/s: Join Date: Sep 2005 Location: Florida Posts: 367	Re: Lower than expected pO2 Were you ever able to get a 1.6 reading at that depth? If your breathing hard and like most of us don't really have 100% and with the normal error rate of the sensors it would not be an unusual reading. __________________ NSS/CDS Training Chairman www.jpjscuba.com
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9th January 2006, 13:25	#8 (permalink)
Sutty Classic Kiss diver Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: Glossop, Derbyshire, UK Posts: 775	Re: Lower than expected pO2 Quote: (Originally Posted by Steve) I saw an issue on the weekend that has me puzzled a bit. I couldn’t get my pO2 above 1.45 at 6m no matter how much I flushed. As far as background goes; I calibrated the Meg with the Meg cal kit with known O2 (99.9999%) and the mV readings were as I would expect. Any thoughts team? How about coming off the loop with readings of 1.45 and dropping a few metres - if PO2 doesn't rise the sensors must be current limited. Its an easy way to check the sensors can read higher than you are willing to breathe too.
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10th January 2006, 18:39	#9 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,662	Re: Lower than expected pO2 When you got out of the water did you pop the head out straight away and check for moisture on the cell faces? I found that when I dive in warm water I get some moisture on the faces and on the final stop I notice some times it reads low - interestingly it never happens in cold water and does not happen to Sarah at all Stuart __________________ Bailout and Kit Management account for Murphy's Law The only bad question is one you did not ask and later wish you had. Use of Rebreather World is subject to the Rebreather World Terms & Conditions of Use
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18th January 2006, 01:18	#10 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Lower than expected pO2 Are you using ISC or Shearwater electronics?
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