CO - how high will you go?

[Griffo]

Well the start of the diving holiday has been interesting. I discovered on my first tank that my analyzer does in fact read above 001 when I got a read of 15ppm on the first tank I tested. Immediately rejecting it, I managed to find two tanks that were down around 7ppm. As the dive was only a first checkout dive to 5m I took them, but was not happy. Stern words with the owner resulted in him extending the snorkel on the compressor input another 5m higher.

Now after the change, the tanks are reading 5ppm. But still, I've never seen a tank over 1 before, and can't help but feel that there is still something wrong with his filter setup.

It's a petrol compressor, but I still feel that the hopcalite should be brining it close to zero.

Am I just being paranoid? Where exactly should I stop worrying about it? Is anything under 10ppm going to be insignificant for rec dives below 30m? What should my ppm per atm cutoff actually be?

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[Scared Silly]

From Analox:

http://www.analox.net/product-docs/manual-91.pdf


2.6 Maximum allowable CO exposure levels
The maximum allowable CO exposure levels for air diving vary in the standards set form one country to another, so you may want to consider referring to the applicable safety standards for your county to determine your maximum allowable CO exposure level.

However, Analox advises that the maximum allowable CO exposure levels should be to that stated in the British Health and Safety Executive (HSE) DVIS9(rev1) document (Diver’s breathing air standard and the frequency of examination and tests (Diving Information Sheet No 9 (Revision 1)).
This states that: Carbon monoxide content shall be as low as possible but not exceed 3 ppm. (For air diving to 50metres)



So for me if

1 PPM a possible fluke/calibration
2 PPM I will grab another cylinder from else where in the stack (i.e. not one that might have been filled with the questionable one). If the same I talk with the owner as they have a problem / if different I talk with owner as they need to check their system but feel comfortable diving it.
3 PPM and above I talk with the owner regardless and the cylinder is rejected.

 

[Wookie]

I like "None detectable", personally. My alarm goes off at 0.3 PPM. It's clear to me that his hopcalite is worn out. Make him a deal. If he changes the filters and direct fills a cylinder and it still reads anything, you'll pay for the filter, as maybe your analyzer is out of calibration. If he changes the filter and it now reads zero, he owes you his undying gratitude for helping save the lives of his clients. You may find more wrong than a short snorkel.

I'd be mortified to death if someone tested one of my fills and found CO in it....

 

[chrpai]

From my googling (I'm not qualified to give an official answer) I find references that Modified Grade E standard is < 2ppm. Web pages suggest any reading over 1.5 should be investigated.

 

[Dr. Lecter]

1 is going to annoy me, 2 or higher would have me insisting on a different tank (from the DM themselves if it comes to it). If it was a choice between dive the tank or sit out, I'd be willing to dive a 2, maybe even a 3, but that's it.

 

[DandyDon]

I think 3ppm is the max allowed in Australia. I suspect he needs to change his compressor oil and use the more expensive synthetic as hot compressors can produce CO internally. https://www.breathingair.com/products/oil-compressor-synthetic They also sell compressor oil for less than half as much, and I suspect that most get it.

Testing tank after tank at 0 ppm can get boring but the first time you read a reading is kind of exciting huh? Thanks for sharing the experience.

 

[Abdullah]

Well the start of the diving holiday has been interesting. I discovered on my first tank that my analyzer does in fact read above 001 when I got a read of 15ppm on the first tank I tested. Immediately rejecting it, I managed to find two tanks that were down around 7ppm. As the dive was only a first checkout dive to 5m I took them, but was not happy. Stern words with the owner resulted in him extending the snorkel on the compressor input another 5m higher.

Now after the change, the tanks are reading 5ppm. But still, I've never seen a tank over 1 before, and can't help but feel that there is still something wrong with his filter setup.

It's a petrol compressor, but I still feel that the hopcalite should be brining it close to zero.

Am I just being paranoid? Where exactly should I stop worrying about it? Is anything under 10ppm going to be insignificant for rec dives below 30m? What should my ppm per atm cutoff actually be?

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Just curious - Did the gas taste or smell odd or different? CO is odorless, but products of incomplete combustion (PIC) can be perceived at pretty low levels.

 

[Superlyte27]

I pretty much consider a 1 to be a fluke in the machine... sometimes.
Anything over 1 and I wouldn't dive it.

 

[Griffo]

Thanks all.

Internet here is not good at all so the reply will be brief. I didn't dive the tanks, so I have no idea if they tasted funny at all. We dumped everything, increase the snorkel length, and got it down to 4ppm. New hopcalite is next but I have the feeling they might not have any more - this is a pretty remote island.
The dive guy is far more worried than the owner, he has been incredibly apologetic and is actually quite concerned for his own safety, but he has to ask permission to change the hopcalite "before normal". It's that kind of place.

I'm not diving for 2 days And won't be again here if they don't change the hopcalite, it just depends I guess on how much they want my dive business. Lucky I'm flat out organising other stuff and have had far less time for diving than i thought, or I'd be going mental at the owner and asking for a full accommodation refund.


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[clownfishsydney]

OzGriffo, where are you diving?