Carbon Monoxide: Near Miss?

[DandyDon]

The physical impact of those readings seems low to me - without any expert knowledge. If you’re reading 50ppm so 200 ppm I’d wager you’d get more than a slight headache.

There was an excellent discussion about CO exposure here the other day that I could sorta understand, in parts anyway. I think Duke Dive Medicine said in hyperbaric treatments they have a better chance of saving a victim of short but high CO exposure than one of long term low exposure. Ah, I was lucky to find the post: CO Poisoning Question

Another thing to bear in mind - from memory so please someone correct me if I’m wrong - is that ascent after CO poisoning is also not ideal. Does CO bond to the alveoli tighter than O2 so as well as being poisoned you PPO2 is also dropping...

I can speak to a part of that. Ascending after a serious CO hit at depth will cause a decrease in PPO while CO stays bound to your blood so it's going to get worse before it gets better. Read that whole thread for a better explanation.

If I’m mistaken with this anyone with the knowledge please correct me.

Well, that's my answer until they show up.

 

[Jafo19D]

Figured I would post about an incident involving Carbon Monoxide, for documentation and everyone else's benefit. This occurred last summer, but since this type of incident is apparently very rare, I am posting it; feel free to move if this is the wrong section.

Last summer I went with some friends to Capurganá, a rural village in Colombia. I was definitely more precautious than most other travelers: I found and booked a PADI certified shop in the village ahead of time, and brought a Cootwo carbon monoxide/o2 analyzer with me.

The day of the first dive, I immediately started checking tanks at the diveshop, and each tank was INCREDIBLY high in carbon monoxide. I was almost in disbelief as I had only seen reports of ~10-20ppm on the forum. My analyzer read 50ppm and the number itself started flashing, which from my understanding indicates an even higher value (meaning I had exceeded the max reading).

I never thought through what I would do if a CO test actually failed, but prepare for an awkward situation if this ever happens to you (since you're essentially insulting a diveshop's equipment, from their perspective). I obviously didn't dive, but the divemasters were adamant that they had dived on these tanks multiple times a day without issue. They were convinced my sensor was inaccurate, so I had them blow into the top with their own lungs to see the CO count lower. They said that they had never heard of carbon monoxide before ("are you sure you don't mean carbon dioxide?"). I actually brought up a chart on my phone from the British navy with various ppm safety threshold recommendations for them to take it any seriously.

One of the divemasters was a bit more open with me, and eventually they started investigating the cause of the issue. Turns out that the entire village was running off of generators from a power outage, and they had positioned the compressor intake in a backyard which a high CO count, probably near the exhaust of a neighbor's generator. I assume this issue didn't start the day I arrived, since the village had been running off generators for several days before. I actually held the sensor around the compressor intake, and the ambient CO was still at a level that caused my sensor to flash. I wish I could find a better photo, but I can only find where the display is mid-flash..

View attachment 580390

The story ends with me going with a different diveshop for a day, while I left the sensor with the original one so that they could to lower the reading. They were able to get their CO readings down to 10ppm, which was still unacceptable to me, by changing the compressor intake position. They finally got it down to 2ppm which I was willing to accept since I had several dives booked already.

Probably the most interesting data from this story is that I had measured nearly every tank in the shop as originally 50ppm+. While all this drama was going on, the diveshop continued to dive with those tanks! And as far as I can tell, no one died. I guess CO poisoning during scuba is just not well studied and unpredictable? Definitely a risk I'm not willing to take!

How's the diving there and what's the name of the dive shop so that I can avoid them? I live in Colombia so I'm actually very interested.

 

[RedyTedy]

How's the diving there and what's the name of the dive shop so that I can avoid them? I live in Colombia so I'm actually very interested.

Honestly, underwhelming, but that was the only place I dived in Colombia and I had very high expectations. The shop was called "Dive and Green". They seemed like the most organized/official diveshop in the area, but the compressor setup itself is just as janky as what the rest of the dive services in the village use.

 

[John C. Ratliff]

The physical impact of those readings seems low to me - without any expert knowledge. If you’re reading 50ppm so 200 ppm I’d wager you’d get more than a slight headache.

Another thing to bear in mind - from memory so please someone correct me if I’m wrong - is that ascent after CO poisoning is also not ideal. Does CO bond to the alveoli tighter than O2 so as well as being poisoned you PPO2 is also dropping...

If I’m mistaken with this anyone with the knowledge please correct me.

Please note that CO doesn't "bond" to the air sacs (alveoli) at all. It simply diffuses through the two cell layers (alveoli and capillary).. CO does bond to red blood cells, at a higher rate than oxygen, and thereby causes the toxicity.

SeaRat

 

[John C. Ratliff]

Rather than going to Wikipedia, where information is pretty good but is put together by a number of individuals who may or may not be qualified to write about the topic, please for chemical information go to the NIOSH Pocket Guide for chemical hazards. Here is their page on carbon monixide:

OG Title

SeaRat

 

[John C. Ratliff]

I started diving in 1959, it was before instruction was available locally (Salem, Oregon), and my first book that instructed me in diving was The Silent World, by at that time Captain J. Y. Cousteau with Frédéric Dumas (Harper & Brothers Publishers, New York, Copyright 1953. Chapter Five of that book is titled "Cave Diving," and describes some of the first aqualung dives ever made in caves by Cousteau's team, dives that almost ended his and Dumas' lives. Why? CO poisoning. If you get a copy, there are pages of descriptions of the symptoms they were experiencing. I won't describe those symptoms, but if you can get your hands on a copy, it makes for intense reading. When they got done diving that day (in 1948), he described the drive home:

...Simone, Didi and I drove back to Toulon that night, thinking hard, despite fatigue and headache. Long silences were spaced by occasional suggestions. Didi said, "Narcotic effects aren't the only cause of diving accidents. There are social and subjective fears, the air you breathe..." I jumped at the idea. "The air you breathe" I said. "Let's run a lab test on the air left in the lungs."

The next morning we sampled the cylinders. THe analysis showed 1/2000 of carbon monoxide. At a depth of one hundred and sixty feet the effect of carbon monoxide is sixfold. The amount we were breathing may kill a man in twenty minutes. We started our new Diesel-powered free-piston air compressor. We saw the compressor sucking in its own exhaust fumes. We had all been breathing lethal doses of carbon monoxide..."

I just did the math, and 1/2000 CO is the same as 500 parts per million (ppm). So on the surface, it was 500 ppm, but what was it at 160 feet depth. Well, 160 divided by 33 feet per atmosphere equals 4.85 atmospheres, plus the surface atmosphere is 5.85 atmospheres absolute pressure. So his assumption of 6 times the surface concentration is very close to correct under Dalton's law of partial pressures.

500 ppm x 6 = 3000 ppm at a depth of 160 feet (actually, 2925 ppm, but rounded it's 3000 ppm).

If you look at the NIOSH Pocket Guide for Chemical Hazards page on Carbon Monoxide, you can see the the Immediately Dangerous to Life and Health (IDLH) for CO is 1200 ppm. So Cousteau was correct in saying that breathing 500 ppm CO at 160 feet was "...breathing lethal doses of carbon monoxide..."

SeaRat

PS, Cousteau, in this same book, has a photograph of them surfacing from the cave's waters, and states that Dumas passed out at 200 feet depth. That's an absolute pressure of 7 atmospheres, and 500 x 7 = 3500 ppm CO that they experienced at that depth.

PS2, the multiplication factor is for partial pressures; it is as if they were breathing those quantities at the surface. The Cousteau team was still breathing 500 ppm, but because of the increased density of the air at depth, it is as if they were breathing 3000 ppm at the surface.

 

[AfterDark]

I started diving in 1959, it was before instruction was available locally (Salem, Oregon), and my first book that instructed me in diving was The Silent World, by at that time Captain J. Y. Cousteau with Frédéric Dumas (Harper & Brothers Publishers, New York, Copyright 1953. Chapter Five of that book is titled "Cave Diving," and describes some of the first aqualung dives ever made in caves by Cousteau's team, dives that almost ended his and Dumas' lives. Why? CO poisoning. If you get a copy, there are pages of descriptions of the symptoms they were experiencing. I won't describe those symptoms, but if you can get your hands on a copy, it makes for intense reading. When they got done diving that day (in 1948), he described the drive home:

I just did the math, and 1/2000 CO is the same as 500 parts per million (ppm). So on the surface, it was 500 ppm, but what was it at 160 feet depth. Well, 160 divided by 33 feet per atmosphere equals 4.85 atmospheres, plus the surface atmosphere is 5.85 atmospheres absolute pressure. So his assumption of 6 times the surface concentration is very close to correct under the law of partial pressures and Boyl's Law.

500 ppm x 6 = 3000 ppm at a depth of 160 feet (actually, 2925 ppm, but rounded it's 3000 ppm).

If you look at the NIOSH Pocket Guide for Chemical Hazards page on Carbon Monoxide, you can see the the Immediately Dangerous to Life and Health (IDLH) for CO is 1200 ppm. So Cousteau was correct in saying that breathing 500 ppm CO at 160 feet was "...breathing lethal doses of carbon monoxide..."

SeaRat

PS, Cousteau, in this same book, has a photograph of them surfacing from the cave's waters, and states that Dumas passed out at 200 feet depth. That's an absolute pressure of 7 atmospheres, and 500 x 7 = 3500 ppm CO that they experienced at that depth.

The courage these men had cannot be overstated.

 

[RayfromTX]

I have tested several tanks that were too high on a live aboard in Oman right next to tanks that read 0. I have tested one in Cozumel that flashed the TOO HIGH alert on my cootwo. All the other tanks on the boat tested fine. I don't dive it if it is near 10ppm or higher. It isn't because of the CO at levels that low. It is because I don't know where the CO came from and suspect it was combustion inside the compressor from oil oxidizing in a hot compressor and not being properly filtered.

For me 50ppm of CO isn't the problem. If it was I would never sit near a camp fire. Heck, smokers exhale 17-20 ppm when they aren't smoking. The problem for me is the combustion of petroleum and all the nasties produced that I don't want in my tank.

CO is a serious problem. It is also an indicator of things in the air that we aren't equipped to test for.

Diving isn't something we have to do right now. If the tank is questionable, I can wait. Others will dive it and may show no signs of being affected. Lots of people have breathed tainted tanks and survived. Some have died. Others have been affected and didn't know what it was.