Acceptable CO Level?

[RN]

On edit, I don't think 0 PPM of CO is achievable from diving gasses, not at least economically anyway, I think to truly get to 0 PPM, all the gases would have to be liquefied and fractionally distilled? Or is there some type of chemical that would filter out CO, like sorb does CO2?

You're somewhat correct but even my quarterly gas analysis shows CO content at less than 0.3 ppmv. CO analyzers are accurate to 1 ppm so anything less than 0.3 ppm will show up as a 0.

My O2 regularly reads about 6-7ppm since CO is a trace contaminant of cryogenic O2 production. Its removed by my compressor filter when continuous blending. And diluted to non-detectable levels when doing most partial pressure blending. Boosted O2 for deco does have 6-7ppm in it though. I am fine with that since I'm not breathing that gas deeper than 20ft anyway.

Interesting. I also check my O2 and it reads 0 ppm every single time. I would be concerned if I saw CO in my O2. As far as I'm aware, standards are for 10 ppm or less in scuba air an 3 ppm or less in oxygen compatible air.


To the OP, I found 8-10 ppm in some tanks while on vacation. I spoke with the boat captain and he apparently told the fill station and they changed the filters that night because the next day the readings were 3-4 ppm. When I'm out of the country I will accept up to 10 ppm if I am diving recreationally, 3 ppm if I am doing deeper than recreational depths. For my home fill station anything different than a 0 is unacceptable.

[rjack]

You're somewhat correct but even my quarterly gas analysis shows CO content at less than 0.3 ppmv. CO analyzers are accurate to 1 ppm so anything less than 0.3 ppm will show up as a 0.



Interesting. I also check my O2 and it reads 0 ppm every single time. I would be concerned if I saw CO in my O2. As far as I'm aware, standards are for 10 ppm or less in scuba air an 3 ppm or less in oxygen compatible air.


To the OP, I found 8-10 ppm in some tanks while on vacation. I spoke with the boat captain and he apparently told the fill station and they changed the filters that night because the next day the readings were 3-4 ppm. When I'm out of the country I will accept up to 10 ppm if I am diving recreationally, 3 ppm if I am doing deeper than recreational depths. For my home fill station anything different than a 0 is unacceptable.

Well my analyzer was behaving erratically for awhile so its possible my contamination issue was due to the analyzer not the gas. Its since been repaired under warranty. But O2 is not as pure as you might want it to be. I haven't looked at the specs in mine for awhile but I recall it being less than 0.1% other gases. so 10 millionths is perfectly acceptable contamination as far as the plant is concerned. Oxygen compatible air is cleaner.

Analyzers are typically calibrated at 100ppm. And then behave roughly linearly down to zero. The problem is the sensor doesn't actually read "nothing" in the affirmative. I think if you are insisting on reading zero (not just displaying zero) you need something alot more sophisticated than a ~$300 single point calibrated analyzer. That's why I give mine a little (3ppm) wiggle room for excess flow rate/pressure on the sensor or just exhalation etc. Mine mostly alternates between 0 and 1ppm, guess that means its trying to report 0.5ppm

[OFG-1]

I always thought that there was a wide range of acceptable CO levels for different people, such as yourself, ex wives, lawyers, politicians (about 1250ppm), reality show stars (2000 ppm) and the like. Have I got this wrong?

[Angry Turtle]

I always thought that there was a wide range of acceptable CO levels for different people, such as yourself, ex wives, lawyers, politicians (about 1250ppm), reality show stars (2000 ppm) and the like. Have I got this wrong?

you got your reality show stars and politicians numbers mixed up, but that's ok for our purposes.

[Randy Thornton]

Interesting use if old soda lime, (I recycle by adding it to casting cement for my art) My question is that I was made aware that soda lime doesn't remove CO just CO2? SO I would think that the COA would be remover to a certain degree but not the CO. Please let me know how the experiment works.

Hi MichaelAngelo, You are correct. The sofnolime will not remove CO. Our regular Hopcalite filters remove the CO. We are adding the sofnolime filter as an additional safeguard to remove CO2 since it is not effectively removed by the Hopcalite filters. I'll let everyone know how it works out.

Regards,
Randy

[FW]

Hi MichaelAngelo, You are correct. The sofnolime will not remove CO. Our regular Hopcalite filters remove the CO. We are adding the sofnolime filter as an additional safeguard to remove CO2 since it is not effectively removed by the Hopcalite filters. I'll let everyone know how it works out.

Regards,
Randy

I would worry more about the foul smell found in old sorb, especially it if has been a little wet.

[DGraham]

Wow, I'm sorry I missed this thread all week.

We manufacture CO monitors here at Nuvair. We test each one that goes out with a certified test gas. Each unit that goes out is calibrated with 10 (PPM) certified test gas. Generally we see 0 (PPM) in ambient air and set the alarms on our units to 10 (PPM) of CO. We also have small test kits that we ship out to customers to test their personal units all the time.

Standards are different depending where you are and what you are doing.
Air tests should always be performed regularly and it is best to test AT THE END OF THE FILTER LIFE... that way you are sure of the quality of your air when the filter wears out and not when the filter is new.

CGA GRADE E
(ANSI/CGA G-7.1’97)

CO2 maximum 1000 (PPM)
CO maximum 10 (PPM)
Hydrocarbons maximum 25 (PPM)
Water Vapor 67 (PPM)
Dew Point -50F
Oil and Particles maximum 5 (mg/m3)

O.C.A.
(OXYGEN COMPATIABLE AIR)
(IANTD/ANDI, ‘93)
CO2 maximum 1000 (PPM)
CO maximum 2 (PPM)
Hydrocarbons maximum 25 (PPM)
Water Vapor 67 (PPM)
Dew Point -50F
Oil and Particles maximum .1 (mg/m3)

CANADIAN
(CAN3-Z180, 1-M85)

CO2 maximum 500 (mL/m3)
CO maximum 5 (mL/m3)
Hydrocarbons maximum 25 (PPM)
Water Vapor 27 (mL/m3)
Dew Point -53C
Oil and Particles maximum 1 (mg/m3)
Nitrogen Dioxide maximum .3 (mL/m3)
Nitrous Oxide maximum 2.5 (mL/m3)
Hal. Hydrocarbons maximum 5 (mL/m3)



Most filtration systems these days do have Hopcolite in them. And that works very well to convert CO to CO2 as long as it is dry and not overheated as Jim said. Moisture is something that needs to be monitored regularly. CO2 obviously needs to be watched. Come by the booth at DEMA and see the full line of analyzers and pick up the information. I won't be there, as someone has to tend the store, but the guys will be able to explain everything to anyone that wants the information.

Danny Graham
Production Manager
Nuvair
2949 West 5th St
Oxnard, CA 93030
805-815-4044
805-815-4196 fax
www.nuvair.com
danny@nuvair.com

[DGraham]

Hi MichaelAngelo, You are correct. The sofnolime will not remove CO. Our regular Hopcalite filters remove the CO. We are adding the sofnolime filter as an additional safeguard to remove CO2 since it is not effectively removed by the Hopcalite filters. I'll let everyone know how it works out.

Regards,
Randy

Randy,
I would position this between your membrane and the compressor. the membrane allows "concentration" of CO2 due to the size of the molecule. The CO2 travels with the O2 through the membrane. I have seen concentration of CO2 from 350 (PPM) up to 700 (PPM) when running a 40% mix.

I like the idea of using the old sofnolime for this. (While the point Forrest makes is valid) We have designed a scrubber for our Canadian customers because their standard is less than ambient air in some situations. In Australia, their standard is very difficult also, so we have been shipping commercial systems with scrubbers installed for the last year or so.

Danny Graham
Nuvair

[Randy Thornton]

Randy,
I would position this between your membrane and the compressor. the membrane allows "concentration" of CO2 due to the size of the molecule. The CO2 travels with the O2 through the membrane. I have seen concentration of CO2 from 350 (PPM) up to 700 (PPM) when running a 40% mix.

I like the idea of using the old sofnolime for this. (While the point Forrest makes is valid) We have designed a scrubber for our Canadian customers because their standard is less than ambient air in some situations. In Australia, their standard is very difficult also, so we have been shipping commercial systems with scrubbers installed for the last year or so.

Danny Graham
Nuvair

Hi Danny, thanks for the suggestion. We'll have to see how that works for us given our space limitations. I will probably give you a call to chat about this.

Forest, I agree with you. We would need to be selective about the condition of the used Sofnolime for purposes of this filter.

Regards,
Randy