Cozumel Diving 2/26/12 - Had one tank read 12 ppm CO -

[markmantei]

Proof of service? What do you have to do, carry around your old o-rings?

An iron lung is a life-support system. A reg is just a way to breathe underwater at depth.

Finally a post I can agree with you on. As certified divers it is our responsibilty to ensure that we are going to get back on the boat after our dive. There are many skilled and experienced divers on this board who service their own gear, how would they "prove" that their gear has been serviced in the past year. What about reg sets that have 2 year service intervals (Atomic and HOG are two that I know of). We do not need or want the SCUBA police, but that does put more responsibility on the shoulders of the individual diver.

It is each diver's decision how much or how little risk they would like to partake in. Yes, many divers have gone their whole carreers without checking for CO and have survived, but at the same time others have died because they did not perform this simple check. Mossman and stevep4444 it is your right not to test your tanks, and you'll probably be fine. I don't begrudge you for choosing to trust that your gas is safe, but others here would like a little more certainty and there is nothing wrong with that either. Its a cheap bit of insurance that I will continue to have on every dive, every tank.

 

[Rkelleyj]

So what is an acceptable ppm for CO??

I assume 0 is the best answer of course..

 

[markmantei]

So what is an acceptable ppm for CO??

I assume 0 is the best answer of course..

Ultimately we must each decide what we are willing to dive. Since Canadian limits are 5ppm for SCUBA, that is my cut-off (some countries are as low as 3ppm, US I believe is 10ppm), but that decision is generally speaking out of laziness and trusting that someone else put a little more thought into it than I have, than out of a particular scientific basis. However, knowing that CO exposure gets worse as you go deeper, cutting back on planned depth and time would definitly be an option with lower concentrations.

 

[jbtut]

Yes I do check nitrox. I would compare it like this. I wear a seatbelt while driving a car but don't wear a helmet. Do you wear a helmet while driving your car? It is safer isn't it?

We each draw the line within our own comfort level. Your choice. Enjoy your day!

This is one of the few forums that we can actually have a discussion without turning into name calling and childish behavior. I like it!

I'm surprised there isn't a single unit that will do a full air analysis. The actual CO sensor is only $10 or so. I'm not sure what it would take to integrate them so a single tool would do both.

 

[Mossman]

Is it fair to assume that you don't check your nitrox mix either? If you do I'd be interested in the logic of checking the mix but not the CO.

While I'm a habitual nitrox tester, I actually didn't check my nitrox mix on my last dives in Cozumel. Not my cup of tea, but there wasn't an analyzer on the boat and I didn't bring my own. Still, faced with the choice of sitting out the dives versus risking my life based on someone else's analysis, I'll choose to risk my life almost every time. I'm going to order a new O2 sensor for my old analyzer before my April trip and bring it with me this time.

The difference is that, especially with partial-pressure blending, it's easy to get the mix wrong. When multiple tanks are being filled/analyzed, it's easy to mislabel a tank. Heck, even when there aren't so many tanks being filled, it's easy to mislabel a tank. We picked up tanks from a south Florida dive shop once, right at closing time so we didn't analyze them at the shop. Fortunately I had brought my analyzer with me that time and when I checked the tanks the next day, we noticed that the 35% and the 28% mixes had their labels switched. Had I not analyzed the tank, poor J would have exceeded a ppO2 of 1.8 when we hit the sand at 140' diving the Spiegel Grove. Given the time we actually spent at depth, I doubt that would have killed her. However, when oxygen toxicity hits, it's not a matter of getting a headache or nausea, it can cause a seizure at depth which ultimately leads to drowning or embolism unless a rescue is successful.

When filling tanks, it's the object of decent fill stations to minimize CO and other contaminants in the tank by using filters, oil-free compressors, strategically located air intakes, etc. On the other hand, when partial-pressure blending, the fill station is deliberately introducing the "poisonous" oxygen into the tank. With CO, the idea is to analyze to see if there is accidentally a level of CO that is too high for comfort. With nitrox, you already know there will be a significant amount of oxygen in the tank, the question is how much. Even in Cozumel, the vast majority of tanks do not have CO levels high enough to concern divers no matter how deep they go. On the other hand, 100% of nitrox tanks filled on the island will have a dangerous level of oxygen if the diver exceeds a certain depth. That certain depth can only be determined by analysis of the gas, so analysis is absolutely necessary with inaccurate partial-pressure blending and still a very good idea even diving nitrox pumped from banked gas or a membrane system. The need to measure is absolute and it's usually done at the filling station. The reason why a diver re-checks the mix is because he doesn't want to trust the busy filling station to get it right all the time. (Besides calculating MOD from the mix, it also determines the dive computer setting. If the mix is actually lower than the computer setting, the diver runs the further risk of unknowing incurring a deco obligation.)

So while CO and nitrox are both gases, they're apples and oranges as far as measuring fruit goes.

 

[markmantei]

While I'm a habitual nitrox tester, I actually didn't check my nitrox mix on my last dives in Cozumel. Not my cup of tea, but there wasn't an analyzer on the boat and I didn't bring my own. Still, faced with the choice of sitting out the dives versus risking my life based on someone else's analysis, I'll choose to risk my life almost every time. I'm going to order a new O2 sensor for my old analyzer before my April trip and bring it with me this time.

The difference is that, especially with partial-pressure blending, it's easy to get the mix wrong. When multiple tanks are being filled/analyzed, it's easy to mislabel a tank. Heck, even when there aren't so many tanks being filled, it's easy to mislabel a tank. We picked up tanks from a south Florida dive shop once, right at closing time so we didn't analyze them at the shop. Fortunately I had brought my analyzer with me that time and when I checked the tanks the next day, we noticed that the 35% and the 28% mixes had their labels switched. Had I not analyzed the tank, poor J would have exceeded a ppO2 of 1.8 when we hit the sand at 140' diving the Spiegel Grove. Given the time we actually spent at depth, I doubt that would have killed her. However, when oxygen toxicity hits, it's not a matter of getting a headache or nausea, it can cause a seizure at depth which ultimately leads to drowning or embolism unless a rescue is successful.

When filling tanks, it's the object of decent fill stations to minimize CO and other contaminants in the tank by using filters, oil-free compressors, strategically located air intakes, etc. On the other hand, when partial-pressure blending, the fill station is deliberately introducing the "poisonous" oxygen into the tank. With CO, the idea is to analyze to see if there is accidentally a level of CO that is too high for comfort. With nitrox, you already know there will be a significant amount of oxygen in the tank, the question is how much. Even in Cozumel, the vast majority of tanks do not have CO levels high enough to concern divers no matter how deep they go. On the other hand, 100% of nitrox tanks filled on the island will have a dangerous level of oxygen if the diver exceeds a certain depth. That certain depth can only be determined by analysis of the gas, so analysis is absolutely necessary with inaccurate partial-pressure blending and still a very good idea even diving nitrox pumped from banked gas or a membrane system. The need to measure is absolute and it's usually done at the filling station. The reason why a diver re-checks the mix is because he doesn't want to trust the busy filling station to get it right all the time. (Besides calculating MOD from the mix, it also determines the dive computer setting. If the mix is actually lower than the computer setting, the diver runs the further risk of unknowing incurring a deco obligation.)

So while CO and nitrox are both gases, they're apples and oranges as far as measuring fruit goes.

I have to disagree, evidently both can be deadly, and I think its fair to say that using the very unscientific meathod of looking at recent accidents on this board there have been more fatalites from CO poisioning than incorrectly labeled nitrox tanks.

 

[Rkelleyj]

Thanks for the reply, I've learned alot from this thread.

Seems a downright silly discussion to be having as to whether there's value in checking your tanks for CO. No fill station or shop would ever want to be accused of sending bad air, very unlikely that anyone will find out anything regarding air in this case ..sad to say.

 

[Mossman]

I have to disagree, evidently both can be deadly, and I think its fair to say that using the very unscientific meathod of looking at recent accidents on this board there have been more fatalites from CO poisioning than incorrectly labeled nitrox tanks.

You are correct that citing a handful of unproven anecdotes is definitely unscientific. Also, if nitrox tanks were as routinely untested as are tanks for the presence of CO, fatalities would skyrocket. Because of the extreme risk, nitrox testing is uniform. Most tanks are tested twice, often three times or more by the time the diver starts to inhale. Uniform testing of CO might cut down on a handful of fatalities a year if that. As I've stated before, the risk of CO poisoning is less than that of an "undeserved" DCS hit. It's so low as to be barely quantifiable, and given the other unmitigated risks divers face, it just doesn't seem worthwhile for some of us to bother with an insignificant risk. Obviously YMMV.

 

[markmantei]

You are correct that citing a handful of unproven anecdotes is definitely unscientific. Also, if nitrox tanks were as routinely untested as are tanks for the presence of CO, fatalities would skyrocket. Because of the extreme risk, nitrox testing is uniform. Most tanks are tested twice, often three times or more by the time the diver starts to inhale. Uniform testing of CO might cut down on a handful of fatalities a year if that. As I've stated before, the risk of CO poisoning is less than that of an "undeserved" DCS hit. It's so low as to be barely quantifiable, and given the other unmitigated risks divers face, it just doesn't seem worthwhile for some of us to bother with an insignificant risk. Obviously YMMV.

While it sounds like we agree that O2 testing reduces fatatlities, it is apparent that you do not agree that CO testing would have the same result.

 

[Mossman]

While it sounds like we agree that O2 testing reduces fatatlities, it is apparent that you do not agree that CO testing would have the same result.

But I do agree. If CO testing was 100% uniform around the world, a handful of fatalities around the world might be avoided. I'm just not sure what cost this might have. Sure, large filling facilities like the ones in Cozumel and big dive ops like Aldora might be able to afford the necessary equipment, but many dive operations around the world aren't so well off that they can easily afford the latest gizmos. Do we put thousands of dive operations out of business in order to save a handful of divers? (Please consider that, unlike in Cozumel where there are central filling stations, most dive ops pump their own gas.) It's obviously much harder for a small six-pack dive op who can barely afford to keep up with compressor, boat, and equipment maintenance, pay captain and DM, and still try to take home anything for themselves, to install expensive in-line CO monitors. Testing individual tanks may be feasible, but still not without costs.

I am often willing to pay $10 per tank extra for nitrox, which offsets not only the cost of the oxygen, but also the cost of handling - i.e. testing. Would you pay $5 extra per tank to have CO testing performed? Depending on the number of dives one makes per year, buying and maintaining a CO analyzer can easily add that much or more to per tank cost.

My benefits from diving nitrox are many: longer bottom time, shorter surface interval, less incidence of sub-clinical DCS symptoms, cleaner air and tanks, and personally I think it tastes better. On the other hand, paying your $5 or so extra for the CO-analyzed tank will not provide any benefits well over 99% of the time. I like value for my money and would much rather apply that $5 toward a margarita. Paying something for nothing doesn't appeal to me. But, once again, YMMV.