I just got back from an awesome diving/research/teaching trip to the Dominican Republic. Before I left, I discovered my CO sensor was toast and had to scramble to find a replacement (found one). Before I found the sensor online, however, I called several dive shops. In Tulsa OK, two dive shops told me they had never used one. One eventually clarified that they had one on their compressor, but had no portable testers. The man at the other shop (Poseidon Adventures) said he'd never heard of a CO sensor!! Granted, these shops aren't anywhere near a beach, but they do certify OW divers and organize dive trips. Do rec divers not know about CO? or care? A post (link) on the "ask an expert" section of ScubaDiving magazine's website says this about the risk of CO poisoning: "CO in your tank should be no more concern than the cleanliness of a restaurant kitchen" and "if you want to avoid a dive accident, your energy would be better spent watching your SPG, and diving within your training and experience, rather than worrying about carbon monoxide." These big statements in a far-reaching publication is at odds with many tragic, or near-miss stories: fatality-Brendan's story, fatality-Vance's story, 4 potentially CO-caused fatalities, reports of high levels of CO detected (and here: 10ppm), read another forum post about dangers here.
On my trip I tested every tank, and was delighted to find there is at least one shop in Bayahibe (Dominican Republic) that is SUPER diligent about maintaining their all-electric compressor, and I consistently got 0ppm from everything they filled. I then found one tank that was filled elsewhere with 20ppm. We emptied that tank, though some people I spoke with said they'd dove tanks with higher CO levels than that, even in the hundreds! It prompted me to look into the levels thought to be dangerous. Wikipedia describes standards for open air environments maxing out at 50-100ppm before evacuation is required but cite time and barometric pressure (ATA 1 in open air) as forces that compound the risk. Respondents to the CDF thread don't like to see more than about 2-5ppm in their breathing gas while diving, I found one agency (can't find the link now) that said 10ppm is the maximum safe level for breathing gas for scuba, analyzers typically alarm at that 10ppm level (e.g., Oxycheq), while the maximum reading by the Analox tester is 50ppm (suggesting this is well above the level at which a user is expected to reject the gas). The danger of CO is compounded by depth, which means that many of the measures thought to be ok for a limited time in open air are significantly more dangerous when scuba diving (divingmedicine.com). That said, there appears to be some disparity between the numbers thought to be dangerous by divers and those reported by some sources. For instance, the above-cited diving medicine site says that 400ppm produces little ill-effect until it is multiplied by depth. Well, what if we only have 50ppm? 50ppm at 20 meters acts like 150ppm. Another factor is time, as CO toxicity has a cumulative effect that can overlooked by reviewing the numbers. Taking this 150ppm level into consideration with time, it is nearly twice that recommended by the WHO for sustained breathing for 15 minutes (as quoted by wikipedia). Fatal? maybe not. Toxic? YES. Is 50ppm the most you'll ever find? One regrettable absence in many of the fatality reports is that they don't report the actual values of the tested gas after the fact. Usually it just says "toxic levels" of CO. I've been told by some divers that they dove in remote locations where the only gas they could find was 100ppm+ and they did it, and came back alive. So, I dunno! I once met a man who's parachute failed him and he hit the ground without it...he got pretty messed up, but there he was, across the table from me at breakfast telling me the story. Does that mean that parachutes are optional?
Scuba diving is an unnatural thing. We are entering a world that is not hospitable to us. There is no air for us to breathe. If we must insist on going anyway (I for one, do), then why would we not make an effort to ensure the gas we bring with us is good? I decided to write this post initially to report my own experience to fellow cave divers on the CDF. But, thinking back about the dive shops I called that were not aware that portable CO analyzers were used for scuba, it got me thinking that another plug for ALL divers to test there gas is never a bad thing. It's clear from many posts on these forums that a lot of rec divers in particular don't test their gas because they trust their shop, because CO poisoning doesn't happen often, or because they just don't know about it. As for not knowing, someone clarified to me that training agencies don't teach to test your gas, but rather to seek reputable dive shops (that, we'd like to assume, are very good about testing their gas..an assumption that proved fatal in some few cases). I hope this and related posts clarifies for the new diver that trusting your diveshop with your gas is trusting them with your life. As for choosing not to test even knowing the risks - What's the point of taking the position that it will never happen to you when it only has to happen once to end you? This is life or death. If someone gave you a sensor would you never use it? Seems like these are more likely excuses hiding the reluctance to pay the money. But think about it, how much money do we spend on this hobby for the fun of it? Is spending another $140-200 or so really such a burden to ensure we are not only moving comfortably and looking cool, but also breathing good clean air? There are cheap testers, and only one is needed for a group.
If you read all the way to the end, thanks and I'm sorry for my tendency to be verbose.
Dive safe.
Originally Posted by MichaelAngelo
. So, I copied it over to the scubaboards with the hope that a couple more people who missed the topic in their OW training read enough of it to ask questions on their next trip. SB post here.
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