No that would not be option 2. The tanks come from an independent fill station already labeled. You're welcome.
Recreational dive poll - Nitrox
- Thread starter billt4sf
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I once did a scuba refresher with a woman who had developed an interesting alternative to the two choices listed in this survey. She was a highly experienced diver, and it had not been all that long since her last dives. In the water, her diving skills were excellent, and I saw her dive, I skipped the normal refresher content to work on more advanced diving.
But it was in setting up her gear that things got interesting. She had all her own gear, including an air integrated computer. I gave her the shop supplied tank, she put her gear on it, and she turned on the air. She looked at the computer and commented that it had successfully identified the gas in the tank as 32% nitrox.
I did a double take. What? She repeated that her computer had analyzed the gas and determined it was 32%. I assured her that her computer did not analyze the gas, and that the tank had nothing but air in it. No, she said, I was wrong. The tank had nitrox in it, because that was how she always analyzed her gas, and it was always right.
I told her that the dive shop through which I was teaching that class did not supply nitrox for swimming pool dives, it did not have any of the equipment in the shop to make nitrox, it did not have any regular employees who could make nitrox, I was the only one in the shop who could do it, and I did not put nitrox in that tank. I assured her that at some point in the past she had successfully analyzed a tank of nitrox at 32%, had correctly set the computer for that level, and had forgotten that between trips. She was apparently always ordering nitrox 32 for all her dives on subsequent trips, so the fact that the computer was set to 32% reinforced her false memory that it was reading the mix for her. Luckily, the mixes she had gotten must have all been reasonably close to 32%.
It took a while, but she eventually believed me.
But it was in setting up her gear that things got interesting. She had all her own gear, including an air integrated computer. I gave her the shop supplied tank, she put her gear on it, and she turned on the air. She looked at the computer and commented that it had successfully identified the gas in the tank as 32% nitrox.
I did a double take. What? She repeated that her computer had analyzed the gas and determined it was 32%. I assured her that her computer did not analyze the gas, and that the tank had nothing but air in it. No, she said, I was wrong. The tank had nitrox in it, because that was how she always analyzed her gas, and it was always right.
I told her that the dive shop through which I was teaching that class did not supply nitrox for swimming pool dives, it did not have any of the equipment in the shop to make nitrox, it did not have any regular employees who could make nitrox, I was the only one in the shop who could do it, and I did not put nitrox in that tank. I assured her that at some point in the past she had successfully analyzed a tank of nitrox at 32%, had correctly set the computer for that level, and had forgotten that between trips. She was apparently always ordering nitrox 32 for all her dives on subsequent trips, so the fact that the computer was set to 32% reinforced her false memory that it was reading the mix for her. Luckily, the mixes she had gotten must have all been reasonably close to 32%.
It took a while, but she eventually believed me.
Saboteur
Contributor
Yes, I've experienced that. I was with an OP this fall with my new nitrox cert ready to try nitrox on my own. I had been on nitrox previously on AOW course under guidance of the instructor. Different OP and island. They were very thorough. Well there was no onboard analyzer for customers to use, just go by the label they said. They didn't even want to see my Nitrox cert. This is all pretty new to me, how often do you see lax safety standards?
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I dive mostly day boats off NC. Many dive Nitrox. A large number bring their own tanks that have already been analyzed including myself. A large number have ordered tanks, some Nitrox, that wait for them on the boat. These are analyzed and marked. However, they are then again analyzed either by the crew with the customer watching or the customer takes the analyzer and analyzes them.
When I first started using Nitrox, it was considered dangerous and we where all considered Nut cases. It was that bad that a lot of boats wouldn't allow the use of Nitrox on the boat.
We basically 'smuggled' Nitrox on to the boat in cylinders without markings, so we all where very pedantic about checking and double checking what was in the cylinders before the regulator went on.
It was so difficult to get Nitrox that often we used to use Air as the bottom gas and 50% in a pony as a flushing gas. Ascend to 20m, switch to 50%, then do your decompression on 50% or at least 5 minutes of safety stops.
It actually worked quite well, you could do a weekend (4 dives) with a pony of 50%. The early computers thought we where on air, so we had a decompression buffer.
Most of us dived twinsets so we still had redundancy. It was before GUE said we where all going to die because we had pony cylinders
.
The first time we used Nitrox as a bottom gas seriously was in Scapa Flow (Scotland), diving the German High Seas Fleet that had been scuttled after the First World War. The depth range is almost perfect, most wrecks are in the 30m zone, the deepest of the big wrecks is in 42m. The procedure is normally a big wreck in the morning (say 36m), then a block ship in the afternoon (say 15-20m).
We got in the habit of a rich mix for the afternoon dive, then air top, giving a weak nitrox mix for the following morning dive.
It made diving a full week of cold water diving far less fatiguing. Especially when we where running a minimum of 30m of decompression on the morning dives, sometimes an hour.
You really are looking for an accident if you don't check then double check your own gas. I have seen to many divers get surprised that they had a different mix in the cylinder than they expected as they assembled kit on the boat.
Gareth
We basically 'smuggled' Nitrox on to the boat in cylinders without markings, so we all where very pedantic about checking and double checking what was in the cylinders before the regulator went on.
It was so difficult to get Nitrox that often we used to use Air as the bottom gas and 50% in a pony as a flushing gas. Ascend to 20m, switch to 50%, then do your decompression on 50% or at least 5 minutes of safety stops.
It actually worked quite well, you could do a weekend (4 dives) with a pony of 50%. The early computers thought we where on air, so we had a decompression buffer.
Most of us dived twinsets so we still had redundancy. It was before GUE said we where all going to die because we had pony cylinders
. The first time we used Nitrox as a bottom gas seriously was in Scapa Flow (Scotland), diving the German High Seas Fleet that had been scuttled after the First World War. The depth range is almost perfect, most wrecks are in the 30m zone, the deepest of the big wrecks is in 42m. The procedure is normally a big wreck in the morning (say 36m), then a block ship in the afternoon (say 15-20m).
We got in the habit of a rich mix for the afternoon dive, then air top, giving a weak nitrox mix for the following morning dive.
It made diving a full week of cold water diving far less fatiguing. Especially when we where running a minimum of 30m of decompression on the morning dives, sometimes an hour.
You really are looking for an accident if you don't check then double check your own gas. I have seen to many divers get surprised that they had a different mix in the cylinder than they expected as they assembled kit on the boat.
Gareth
Saboteur
Contributor
I'd rather not say.
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That's a tragic case of someone not understanding the information their computer was giving them. I've run into that before as well ... particularly with people who do not comprehend what happens to their dive computer once they cross the NDL line. It's almost frightening that these people can dive for so long without hurting themselves ...
... Bob (Grateful Diver)
It also shows something else.
This was a very intelligent human being with an advanced education. She had obviously been taught correctly originally and understood it. She had obviously understood how her computer worked at some point in the past. She had obviously known how to input the nitrox mix into her computer at some point in the past. And at some point in the past, at some time between her annual dive trips, she had forgotten it. She had made what is really not a far-fetched error if you think about it objectively. If a nitrox analyzer can measure oxygen content, is it really so unthinkable that an air integrated computer might have that ability as well?
Think about that the next time you see a diver make a mistake and then have everyone fly off the handle about how miserable the original instruction must have been.
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I experienced a similar situation in Fiji ... the dive crew didn't have an analyzer on board (and none of us had brought one, assuming there would be one available). The dive guide assured us the tanks had been analyzed, and that we should just go by what's on the label. Four of the six of us said no, and insisted they go back for an analyzer. Eventually they hailed another boat and asked if we could borrow their analyzer ... which we used to check our tanks before the dive.
... Bob (Grateful Diver)
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