CO - how high will you go?

[chrpai]

altho the average level for Austin is considered under 1 ppm. Austin, TX Air Quality

The last year sampled in the graph you cited for Austin shows it at about 0.25ppm. That's closer to the 0.1ppm I cited then the "under 1.0ppm" that you cited.

Ignoring the weeds for a moment, what threshold do you use to reject a tank? I haven't gotten an analyzer yet ( I probably should have when you put the ScubaToys deal together last year ) but if I did get one, it's kind of important to have a threshold otherwise why bother?

 

[cruiser]

I'll dive with 1 or 2 ppm CO in a tank, but I prefer none. Last month in Aruba I rented a tank with 4ppm. Took it back and tested until I found a tank with 2 ppm. The guy at the shop said they're allowed up to 6 ppm CO in a tank.

 

[DandyDon]

The last year sampled in the graph you cited for Austin shows it at about 0.25ppm. That's closer to the 0.1ppm I cited then the "under 1.0ppm" that you cited.

Ignoring the weeds for a moment, what threshold do you use to reject a tank? I haven't gotten an analyzer yet ( I probably should have when you put the ScubaToys deal together last year ) but if I did get one, it's kind of important to have a threshold otherwise why bother?

Yeah, I guess so for averages. Calibrate a tester on a known to be clean tank sometime while standing downwind of I-35 when it's full, then tank the flow resistor off and check the wind and I bet you get a much higher reading - more like 3-5. Not a big deal really, but a trend.

Ignoring what weeds? I did not put together that group buy, and I talk about the need for testing so much that I certainly don't want to get involved with any actual sales at any level, but it was a nice one. Diverightinscuba.com has the Analox for $352 & free shipping and your LDS may well be willing to beat that, and there are other brands.
This guy came up with an interesting kit involving a little DIY work, altho I know nothing about the model or company - still, looks appealing. http://www.scubaboard.com/forums/co...relatively-inexpensive-co-detector-setup.html
This just posted today for sale here, new but the sensor may be a year old - I can't read the manufacture date in the pic? Keep in mind that a sensor is good for 3 years or so, and run about $150, so make sure they are recently manufactured when you have to replace: www.scubaboard.com/forums/classifieds-computers-gauges-watches-analyzers/460381-new-analox-carbon-monoxide-analyzer-suunto-guage-set.html

What cut-off threshold? That's a personal call and as I've said before, pick a number between 3 & 15 and stick to it. I wouldn't dive over a 10, but many won't go over 3 - and there should not be any anyway!

I'll dive with 1 or 2 ppm CO in a tank, but I prefer none. Last month in Aruba I rented a tank with 4ppm. Took it back and tested until I found a tank with 2 ppm. The guy at the shop said they're allowed up to 6 ppm CO in a tank.

How interesting. Was the 6 a government limit or a shop standard? The Dutch Indies have been dickering over independence from The Netherlands and I don't think any of the islands can agree on details - none cutting the apron strings completely. Did they have an inline monitor or a tank tester of their own?

 

[chrpai]

What cut-off threshold? That's a personal call and as I've said before, pick a number between 3 & 15 and stick to it. I wouldn't dive over a 10, but many won't go over 3 - and there should not be any anyway!

My memory mis-attributed the group buy to you. But that's a compliment. Thanks for giving your answer.

 

[Abdullah]

Diverightinscuba.com has the Analox for $352 & free shipping and your LDS may well be willing to beat that, and there are other brands.

Amazon/Leisure Pro have the Analox CO meter for $341. I don't think I've seen it anywhere any cheaper than that.

 

[cruiser]

How interesting. Was the 6 a government limit or a shop standard? The Dutch Indies have been dickering over independence from The Netherlands and I don't think any of the islands can agree on details - none cutting the apron strings completely. Did they have an inline monitor or a tank tester of their own?

Don, don't know how they arrived at 6 ppm. I tested the tanks with my own Analox CO monitor that travels with me. Their compressor wasn't visible so can't comment as to their setup.

 

[Subcooled]

Everyone seems to be discussing the maximum allowed concentration (in ppm) of CO,

but isn't it the actual pressure of CO (partial pressure, ppm times depth) that's relevant?

At least it is so for oxygen, nitrogen, argon, helium, ...

 

[DandyDon]

Everyone seems to be discussing the maximum allowed concentration (in ppm) of CO,

but isn't it the actual pressure of CO (partial pressure, ppm times depth) that's relevant?

At least it is so for oxygen, nitrogen, argon, helium, ...

Yes, that has been discussed on this thread. It's the PPM that we can now measure tho.

Other than ANDI and the nitrox it is not clear to me if these standards are for diving as compressed air is used by firemen.


The issue of CO at depth is the partial pressure coupled with bind affinity. I do not know all of the physiology.

Oh 10-20 ppm is nothing at sea level. At depth with partial pressure increase as you mentioned concentrates the effect and much more as we've been discussing.

Most countries do not have regulations, but for the US the max is 10 ppm in tank air, in other countries from 3 to 15 ppm, and for personal calls - pick a number. 3 ppm seems kinda picky to some, but then there should be none in there anyway - and if they allow that much, what else is getting by?

Testing in ppm was the original challenge, but now we have the technology. If you calibrate your tester correctly, like with the Analox - adjust the knob in seemingly clean air, then I'd still take a 1 or a 2 as a false positive. I start complaining at 3 but have knowingly dived tanks up to 5.

 

[Subcooled]

What symptoms does 10 ppm CO cause
- in one hour at the surface
- in one hour at 20m/3ATA
- in ten minutes at 65m/7½ATA
?

Information like this would be usefull.

 

[DandyDon]

What symptoms does 10 ppm CO cause
- in one hour at the surface
- in one hour at 20m/3ATA
- in ten minutes at 65m/7½ATA
?

Information like this would be usefull.

Well, 10ppm at the surface is not going to be much of a bother. It's not a healthy exposure, but you probably wouldn't notice anything. At 20m/65ft it would be biding to the hemoglobin in your blood reducing its ability to carry needed oxygen to your body, and of course at 65m/213ft the toxicity would be more pronounced. Symptoms from CDC - Carbon Monoxide Poisoning - Frequently Asked Questions

The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion. High levels of CO inhalation can cause loss of consciousness and death. Unless suspected, CO poisoning can be difficult to diagnose because the symptoms mimic other illnesses. People who are sleeping or intoxicated can die from CO poisoning before ever experiencing symptoms.

Now while the direct effect of 10ppm CO might well be similar to 30 at 3 ata or 75 at 7.5 ata, reducing oxygen available to your body, and combining with proteins in tissues, destroying the tissues - it's more complicated than that. At depth, the increase in PPO will offset the problem somewhat, but on ascent - PPO drops while the CO stays bound to your blood.

Since CO poisoning mimics other illnesses and problems, the only way to confirm it is to test the blood if the local facilities have that capability, or test the tank air. Testing before you take a tank down is safer.