Nitrox: Should I be worried?

[DandyDon]

I can't for the life of me ever recall an instructor telling me that. I'm pretty sure it's not in the PADI OW manual - but I'll be reading that on the flight down to Roatan and I'll keep my eyes out for it.

You're not going to suck in 50 ppm CO from the street, but your compressor can create it. Smell all you want. You still die.

How many recreational diver deaths/injuries have been attributed to CO poisoning?

I think injuries and deaths from CO are greatly under reported, written off as travelers flu & hangovers or drownings, with tanks drained to protect the local businesses. I have known of several stories where the evidence was quickly destroyed.

The most popular dive resort on Roatan killed a Texan tourist and a popular dive master, then tried to blame the tourist for killing the DM. That did fail tho, so the resort quietly settled with the widow with enough money to include a nondisclosure agreement.

Then there are unfair libel suits. Scubaboard almost went bankrupt because of a discussion including first hand witnesses who tried to save the dying even tho they were injured by CO created by the compressor. The suit was thrown out of court, but it cost a lot to defend up to that point.

 

[Alan Browne]

I think injuries and deaths from CO are greatly under reported, written off as travelers flu & hangovers or drownings, with tanks drained to protect the local businesses. I have known of several stories where the evidence was quickly destroyed.

The most popular dive resort on Roatan killed a Texan tourist and a popular dive master, then tried to blame the tourist for killing the DM. That did fail tho, so the resort quietly settled with the widow with enough money to include a nondisclosure agreement.

Then there are unfair libel suits. Scubaboard almost went bankrupt because of a discussion including first hand witnesses who tried to save the dying even tho they were injured by CO created by the compressor. The suit was thrown out of court, but it cost a lot to defend up to that point.

Which resort? We'll be at Fantasy Island which I'm fairly sure is not the most popular. Coco View is to the northeast of there, and it was putting out 4x as many boats each day, and more often...

(You should edit your reply above before replying).

 

[DandyDon]

Which resort?

You want me to start another libel suit? It doesn't matter. No tank is safe unless checked.

(You should edit your reply above before replying).

I probably should give up trying to expose the guarded secrets. The whole dive profession including DAN is afraid of hurting business.

 

[JackD342]

I can't for the life of me ever recall an instructor telling me that. I'm pretty sure it's not in the PADI OW manual - but I'll be reading that on the flight down to Roatan and I'll keep my eyes out for it.

A quick glance at the manual found the statement that contaminated air may smell bad, on page 191.
I also found a place in the instructor presentation notes that says "do not use air that tastes or smells bad."

But you are right, at first look I don't find anywhere that specifically says to check the odor of your air cylinder. That may just be some hand-me-down procedure that tends to get passed along from instructor to instructor, and certainly nothing wrong with it.

I am continuously amazed at how many experienced divers and professionals do not understand that overheated compressors burning their on lubrication oil are a bigger risk than air intake. You're not going to suck in 50 ppm CO from the street, but your compressor can create it. Smell all you want. You still die.

Sounds reasonable, but you are right that is first time I have heard that specific concern. You also seem to imply that burning compressor oil is odorless. I'm not going to go burn some to check, but I am a bit skeptical in that regard. Thoughts?

And I did not mean to imply that a sniff test is fool proof, just that it is good advice.

 

[Joneill]

Can anyone give me hard numbers? How many recreational diver deaths/injuries have been attributed to CO poisoning? How many recreational diver deaths/injury from diving wrong nitrox mixes?

How many deaths/injuries would make you concerned? These issues are real possibilities so I take precautions and analyze my tanks for mix and CO to make sure I don’t end up as one of those numbers. It’s quick and easy, so why take a chance?

 

[Alan Browne]

A quick glance at the manual found the statement that contaminated air may smell bad, on page 191.
I also found a place in the instructor presentation notes that says "do not use air that tastes or smells bad."

I was skimming and hadn't found it, but yes, there it is on p.191. Thanks.

 

[Storker]

How many deaths/injuries would make you concerned? These issues are real possibilities so I take precautions and analyze my tanks for mix and CO to make sure I don’t end up as one of those numbers. It’s quick and easy, so why take a chance?

Well, there's this thing called calibration. I calibrate my O2 analyzer before every use, because I have easy access to a 20.8-20.9% O2 mix. For calibrating a CO analyzer, I'd need a CO mix with known composition.

So even if I had a CO analyzer, it'd be a bit more faff to ensure I got sensible numbers from it.

 

[diverrex]

I just got certified and I've yet to actually dive Nitrox.

The course made it plain in all the presentation materials, the quizzes, the "simulations" and the exam that thou shalt not dive w/o analyzing the tank yourself. Period. As others point out it may indeed be enriched - but not the mix you're planning or entered into your computer.

Our plan is to return to Roatan this March and to the same resort. On the "certified divers" boat the captain has an analyzer and I've seen divers using it to check their tanks.

That said, there is _nothing_ about the analyzer that we used on our course that would tell you if you have a tank with, for example, CO in it.

This happened to my instructor on a dive in (IIRC Mexico). It appears the fill station's "intake" pipe was on an alley - the fill had been done with idling trucks outside...

I probably shouldn’t open another can of worms, and I agree that all nitrox tanks should be analyzed, but I would’t be surprised if your class also made it clear that all Nitrox tanks should have a big green and yellow sticker wrapped around it. For private tanks often not case.

 

[RayfromTX]

Storker that is true but the calibration gas is 20 ppm. A smoker exhales somewhere around 17ppm which will do in a pinch and should convince smokers to quit if nothing else did. I'm not talking about while smoking. I'm talking that is their constant attempt to offgass all the CO they inhale when smoking.

The sniff test is fine as far as it goes. Won't tell you if you how much CO you have in the tanks but what you are sniffing is probably horrible to breathe in elevated concentrations anyway. The problem with the sniff test is the people that will convince themselves that it is good enough. It isn't and you should do both.

The other reason I hear people use when justifying their willingness to roll the dice on their air supply is that my tank tested good so they don't need to use the tester that I'm offering them. If they won't use the tester that is ready to go and will take them all of 20 seconds to use then that falls in the category of things I will never understand. It happens on every boat ride I'm on. It's like they must think I'm a paranoid wierdo until I get a tank with really high levels and then they might test theirs. Sometimes I just test all the tanks on the boat before anyone shows up if I get there early.

 

[DandyDon]

Sounds reasonable, but you are right that is first time I have heard that specific concern. You also seem to imply that burning compressor oil is odorless. I'm not going to go burn some to check, but I am a bit skeptical in that regard. Thoughts?

I can't say for sure. I can't smell anything. My guess is that an overworked hot compressor can burn enough lubricating oil to produce 50 ppm (think 200 ppm at 100 feet) without smelling enough to alert many. It doesn't hurt to smell your gas, and if you did smell something burned - reject, but in my almost 500 dives I have never noticed anyone do so.