Equipment My first out of air situation
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tmrqs
Contributor
bcaderunr
Contributor
I keep looking at this time series and am trying to understand what might produce this graphic -- and the OP's experience. Since the transmitting sensor connects directly to a high pressure port on the first stage, the only rational explanation that fits the facts is a clogged first stage from debris in the tank.Hello fellow divers. I'm a newcomer to the diving hobby. I got OW certified this year and have only 30 dives .On my 30th dive I experienced an out of air situation. Please help me understand what happened and if I did something wrong.
I am a very cautions about my air consumption and normally I check my air once every couple of minutes. Here is what happened:
I was in a group of 6-8 people diving in Greece. At about 30 minutes from the start of the dive I checked my air and I had around 110 BAR. We were at 22 meters. Couple of minutes later we spotted a nice octopus and I was checking it out and having a super nice time. At about minute 35 I noticed that taking a breath started to require a lot of effort, like something was blocking my hoses. Looking at my computer I saw that I only had 3 BAR left. I immediately went to the dive master and gave him the out of air signal. He understood me and double-checked my computer. He offered me his backup 2nd stage, but I didn't take it immediately, because I was still breathing (harder and harder, but still doable). We slowly started going up. I positioned myself very close to his octo, so that in case I run out of air completely I can grab it relatively quickly. I wasn't in panic at all, but I still had a strange feeling of uncertainty. Shortly after, I ran out of air completely, gave my DM the signal again and he passed me his octo. So far so good, I was finally able to take a normal breath. We continued going up, but from time to time we had to stop and wait for the others, because we were in a very bad visibility. We made it to around 5 meters and we started our safety stop. During the stop I passed him my primary so he can double-check if I was really out of air (by then I was still thinking that maybe I was doing something wrong). He confirmed. At minute 2 of the safety stop I had the same feeling again - taking a breath required a lot of effort and I was not able to take a full breath - clear sign the DM's tanks was running low. We finished our safety stop. By the end of it there was no air inside the tank. That was no problem, we ascended safely and I remembered to blow bubbles on the way up (huge thanks to Gus and Woody from Dive Talk).
I am loosing sleep over what actually happened. Maybe something blew up and all of my gas went out. I don't think so, because I expect such event to be noisy. I didn't hear that. I am a beginner diver and I am working on my trim a lot. That day I noticed that when I was adjusting my trim (upper body going up or down) I was hearing bubbles going out. I was thinking that these were not bubbles, but rather the air inside my BCD moving (how stupid was I....). That happened multiple times. I believe that's how I lost my air. However, these adjustments were happening over a period of time. According to my computer I lost my air in a very short time. I don't know what to trust - what I heard or what my computer is telling me. According to the DM it was sort of malfunction in the regulator, because it was due for a service. I am confusedI am also wondering if I tightened the 1st stage to tank good enough. These were DIN tanks.
What do you think? What possibly happened that day? Have I done something wrong and what can I do to reduce the risk of that happening again? I am buying a set of personal regulators so that I can be responsible for cleaning and maintaining them.
Here is a photo of the air chart for your reference:
View attachment 914044
The receiver in the Op's computer gets a near empty reading as soon as a significant blockage occurs. It appears to have briefly cleared at T=40 only to have "junked up" again a minute later. All the time, the OP is breathing the tank down despite the significant resistance.
A tear-down of the first stage might (and should) reveal the presence of particles or some other solid contaminant. And, shout out to the OP. Thanks for sharing.
Thanks a lot for your reply. That makes sense and is possibly the answer I was looking for. Sadly that was a rental regulator and I cannot take it somewhere to be examined. How can we protect ourselves from situations like you described? Generally, we go to a nice holiday and we almost always get the tanks from the dive shop. Debris from poorly maintained tanks can clog any regulator (in my opinion), regardless of brands, reg design, cost or how well we maintain them.
lizardland
Registered
What was the rest of the dive data? In particular, what was your depth profile and cylinder size?
Going by the chart you've posted and assuming it was a 12l cylinder then that's looking something like 1200 litres of air in around 35 minutes. And if most of the dive was around 20m then that works out to a very low air consumption. Like a hell of a lot lower than you would expect from an inexperienced diver lacking confidence.
The other thing that stands out is that the DM ran out of air after a fairly short period of sharing. That suggests to me that he was actually pretty low on air at the start of the ascent as well.
My guess is that your computer was misreading the pressure and for whatever reason around the 35 minute mark it kicked back in and started showing a true reading. Given that the DM appears to have been low on air then it seems reasonable that an inexperienced diver would be at or near zero without anything disastrous needing to have happened.
A regulator won't fail like that just because it's due a service. At least, a decent regulator that has been looked after won't. If it was a catastrophic leak that you (and everyone else) somehow managed to not notice then that's not just because a reg needed a service. He's fobbing you off and trying to normalise an event that was far from normal. Probably because he realises there was a lot of failings.
If you hadn't tightened the DIN valve then you'd know the minute you turned the air on. It would be undiveable. It won't just work loose during a dive either. If it seats enough to form a seal then the amount of force you have to apply to undo it without turning off the air and purging the reg is substantial. There is always the chance you hit that magic point between seated and unseated but it's extremely unlikely that was the issue.
I can only add to the two main things that others have pointed out. Doing a discretionary safety stop in an out of air situation isn't a gamble I'd take. You can get unbent a lot easier than you can get undrowned. Not taking the octopus when offered was also a mistake for all the reasons pointed out by everyone else.
Going by the chart you've posted and assuming it was a 12l cylinder then that's looking something like 1200 litres of air in around 35 minutes. And if most of the dive was around 20m then that works out to a very low air consumption. Like a hell of a lot lower than you would expect from an inexperienced diver lacking confidence.
The other thing that stands out is that the DM ran out of air after a fairly short period of sharing. That suggests to me that he was actually pretty low on air at the start of the ascent as well.
My guess is that your computer was misreading the pressure and for whatever reason around the 35 minute mark it kicked back in and started showing a true reading. Given that the DM appears to have been low on air then it seems reasonable that an inexperienced diver would be at or near zero without anything disastrous needing to have happened.
According to the DM it was sort of malfunction in the regulator, because it was due for a service. I am confused
A regulator won't fail like that just because it's due a service. At least, a decent regulator that has been looked after won't. If it was a catastrophic leak that you (and everyone else) somehow managed to not notice then that's not just because a reg needed a service. He's fobbing you off and trying to normalise an event that was far from normal. Probably because he realises there was a lot of failings.
If you hadn't tightened the DIN valve then you'd know the minute you turned the air on. It would be undiveable. It won't just work loose during a dive either. If it seats enough to form a seal then the amount of force you have to apply to undo it without turning off the air and purging the reg is substantial. There is always the chance you hit that magic point between seated and unseated but it's extremely unlikely that was the issue.
I can only add to the two main things that others have pointed out. Doing a discretionary safety stop in an out of air situation isn't a gamble I'd take. You can get unbent a lot easier than you can get undrowned. Not taking the octopus when offered was also a mistake for all the reasons pointed out by everyone else.
This thread is going in circles with finger pointing and wind conjecture about debris clogged regulators. A new diver is asking for feedback after a dive mishap. Don't pummel the person. This is how we all learn from mistakes.
The scenario described is exactly the experience of a half opened tank valve. Simplest explanation.
The scenario described is exactly the experience of a half opened tank valve. Simplest explanation.
With a partially closed valve, you are rate limited -- you breath the gaz in the hose in fact -- but the pressure come back when you stop breathing. That's not consistent with the graph.
johndiver999
Contributor
Look at the graph of air pressure. As mentioned by someone else, this shows immediate drop in pressure to zero (and then a spike). This can not happen from a partially opened tank valve. Also, it can not happen if there was a terrible leak, because the diver would have noticed it and the pressure would not spike up again momentarily.
The description I am reading is entirely consistent with a blockage in the regulator - most likely from crude inside the tank and then clogging the regulator.
If the tank valve was partially open, the pressure would have come back up, particularly when the regulator was not being used on ascent.
The Op made a very serious error in not immediately taking the second stage from the DM. There is no good reason NOT to start accepting air right away.
Some reasons why this was not just a failure to do the smart thing, but was dangerous and short sighted. What if the DM octopus was not working? It is much, much better to know that right away and when your regulator is still giving you some air. Also, if it was a typical low on air emergency, then it would make sense to preserve any air in the victims' tank for operation of the BC - or maybe just a breath or two if the DM tank runs out at 15 feet (which it did) apparently..
Also, it would not be a smart assumption that this was a typical low on air emergency and the diver could have just milked the tank slowly while ascending. If the indicated pressure suddenly went to zero, then the tank may suddenly stop delivering any meaningful air.
I would have taken the regulator off and examined the inlet and also tried to verify that the tank was completely out of air when the regulator was off - after the dive. Then I would have put that regulator on another tank and see how it performed.
The description I am reading is entirely consistent with a blockage in the regulator - most likely from crude inside the tank and then clogging the regulator.
If the tank valve was partially open, the pressure would have come back up, particularly when the regulator was not being used on ascent.
The Op made a very serious error in not immediately taking the second stage from the DM. There is no good reason NOT to start accepting air right away.
Some reasons why this was not just a failure to do the smart thing, but was dangerous and short sighted. What if the DM octopus was not working? It is much, much better to know that right away and when your regulator is still giving you some air. Also, if it was a typical low on air emergency, then it would make sense to preserve any air in the victims' tank for operation of the BC - or maybe just a breath or two if the DM tank runs out at 15 feet (which it did) apparently..
Also, it would not be a smart assumption that this was a typical low on air emergency and the diver could have just milked the tank slowly while ascending. If the indicated pressure suddenly went to zero, then the tank may suddenly stop delivering any meaningful air.
I would have taken the regulator off and examined the inlet and also tried to verify that the tank was completely out of air when the regulator was off - after the dive. Then I would have put that regulator on another tank and see how it performed.
I too would like to see the depth graph.
I don't use AI, but the air consumption graph does not make sense to me: it shows a remarkably constant slope, with ~100 bar used in ~35 min. This is regardless of changes in depth during decent or any changes in diver activity. For folks who do use AI: shouldn't there be greater variation in air consumption rate during decent and during the dive, and not a completely straight slope?
100 bar in say a 12 L tank is 1200 L - so the slope of the graph is 1200L/35 min = 34 L/m at 3 bar/20m. That equates to 11 bar/min on the surface: which is far lower than most experienced divers.
However assuming a more typical breathing rate for an inexperienced diver (say 22 bar/min) would empty a 12l tank in ~35 mins: close to what's seen.
As lizardland points out - I think the issue is with the AI/computer.
Cheers
Rohan.
I don't use AI, but the air consumption graph does not make sense to me: it shows a remarkably constant slope, with ~100 bar used in ~35 min. This is regardless of changes in depth during decent or any changes in diver activity. For folks who do use AI: shouldn't there be greater variation in air consumption rate during decent and during the dive, and not a completely straight slope?
100 bar in say a 12 L tank is 1200 L - so the slope of the graph is 1200L/35 min = 34 L/m at 3 bar/20m. That equates to 11 bar/min on the surface: which is far lower than most experienced divers.
However assuming a more typical breathing rate for an inexperienced diver (say 22 bar/min) would empty a 12l tank in ~35 mins: close to what's seen.
As lizardland points out - I think the issue is with the AI/computer.
Cheers
Rohan.
If I were the diver here I would have my first stage and the Air Integration checked by a service center. A faulty AI can create some extremely funky reading, both if water get through the first stage and if the battery is about to fail. I have logs where the reading jumps in literally impossible ways, and I have seen the battery in a AI explode not once but twice. (Not going to argue in replacing AI with a SPG, but when AI fail it will do so in a different way than a SPG. In doubt use both.)
If the actually air had dropped like the graph said then it should had been noticeable by the diver, buddy, DM, or just divers in the area (and marine life in general). It is possible that a new diver could miss it in the stress/distraction of the wonderful new experience of diving, but people around them is less likely to have missed that much of air exploding.
I would not personally put too much stock in that the DM tanks started to feel empty at the end of the dive. After an out of air experience, stress will makes things unreliable at that point. It could be as mentioned by others that the tanks was low from the start, or a very high breathing rate, or simple the stress making it feel like one can not able to take a full breath. The DM could also have been stressed out. With 30 dives, I would not worry much about this part of the events.
If the actually air had dropped like the graph said then it should had been noticeable by the diver, buddy, DM, or just divers in the area (and marine life in general). It is possible that a new diver could miss it in the stress/distraction of the wonderful new experience of diving, but people around them is less likely to have missed that much of air exploding.
I would not personally put too much stock in that the DM tanks started to feel empty at the end of the dive. After an out of air experience, stress will makes things unreliable at that point. It could be as mentioned by others that the tanks was low from the start, or a very high breathing rate, or simple the stress making it feel like one can not able to take a full breath. The DM could also have been stressed out. With 30 dives, I would not worry much about this part of the events.
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