Your problem is that you do not want to accept that some people don’t have a problem with narcosis or gas density at 60m and for them it is a normal dive.
Diving air to 60m
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helodriver87
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You've literally never done the dive without the impairment. Of course you think it's normal. Jesus.
Look, nobody is getting through to you. Do your thing. Just stop pretending it's safer or smarter. The science isn't on your side. I'll tell you what I tell everyone when these topics pop up, because the response is always the same "you may be narced, but I'm not, I can control it, etc". You're not immune to physics or chemistry. That's what's going on here. You're impaired at 60m. Period. You may be able to function fine under most circumstances, but the same chemical processes are happening to you. You just lack the relevant experience to recognize it. And telling other people that it's fine and normal is normalizing a practice that's largely fallen out of favor in technical training because the facts and evidence don't support it.
Look, nobody is getting through to you. Do your thing. Just stop pretending it's safer or smarter. The science isn't on your side. I'll tell you what I tell everyone when these topics pop up, because the response is always the same "you may be narced, but I'm not, I can control it, etc". You're not immune to physics or chemistry. That's what's going on here. You're impaired at 60m. Period. You may be able to function fine under most circumstances, but the same chemical processes are happening to you. You just lack the relevant experience to recognize it. And telling other people that it's fine and normal is normalizing a practice that's largely fallen out of favor in technical training because the facts and evidence don't support it.
Look just for an example, with the setup I have where I can pump, maintain and I own all my own gear I’m going for a dive in the morning and it’s going to cost me 14 euro. and I can do that anytime I like. So at 65 years of age do you believe I will change
beester
Contributor
@mac64 I know a CMAS instructor who made a change and took a trimix course at 70.. (yes the guy with the big hit after a hypercapnia incident, spending time in the decompression chamber in Toulon).
I absolutely have no beef with your way of diving, or what you do... your life, your rules. But I find it very strange that you can profess stuff as being the absolute truth, like the advantages of trimix being a myth, WOB or hypercapnia being a non issue, when frankly you have no experience with any of this stuff. You have never done long deco dives, for crying out loud you do deco on backgas... you never have dived trimix... you have never suffered a CO² incident... so how can you be so sure of yourself. I'm know it's futile to try to change someone on a internet forum, but I don't get why you are not thinking in the back of your mind... "hey, there seem to be a lot of these internet warriors saying the same stupid stuff, let's see if I can start reading up on this, ask questions to some local tech instructors"... even if it's just to learn something and be aware.
Not you ... Trimix is a myth, and people having a hypercapnia incident need to see a doctor, they are not normal.
Most of the time I see people so sure of themselves they are teenagers not 65 year old guys.
I absolutely have no beef with your way of diving, or what you do... your life, your rules. But I find it very strange that you can profess stuff as being the absolute truth, like the advantages of trimix being a myth, WOB or hypercapnia being a non issue, when frankly you have no experience with any of this stuff. You have never done long deco dives, for crying out loud you do deco on backgas... you never have dived trimix... you have never suffered a CO² incident... so how can you be so sure of yourself. I'm know it's futile to try to change someone on a internet forum, but I don't get why you are not thinking in the back of your mind... "hey, there seem to be a lot of these internet warriors saying the same stupid stuff, let's see if I can start reading up on this, ask questions to some local tech instructors"... even if it's just to learn something and be aware.
Not you ... Trimix is a myth, and people having a hypercapnia incident need to see a doctor, they are not normal.
Most of the time I see people so sure of themselves they are teenagers not 65 year old guys.
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This fellow enjoyed the 50-60m air dives too, wasn't exactly a friend but we met at the dive site a few times. He was warned many times, he went along on his merry way for at least a couple years, until one day he didn't.
Should TDI Helitrox replace AN+DP?
Should TDI Helitrox replace AN+DP?
No, the problem is that YOU said it's not an issue for anyone because it's not an issue for YOU in your experience. you discard the science proving it is an issue and that helium IS safer because YOU haven't had a problem yet.
That "some" people might not have a problem isn't the point. The point is that the data, and science, and every other factual piece of material says that while some people "may" be okay on air, divers in general WILL be safer on trimix.
What works for you may continue to work for you forever, to say that science is a "myth" because it you feel fine diving air is just patently absurd however. That's why you can't provide one piece of scientific, objective evidence to support your statement.
Dive how you want to dive, but please don't come to the internet and try to convince people who may not know better that all the scientific evidence is wrong and they should risk their lives based on how your experience has been and contrary to the objective evidence about how to do things safely.
To all people who do not want to read through the whole thread. Most of the guys attacking @mac64 respect his decision on his diving practices, but his generalizing statements based on subjective feelings lack any trimix experience and ignore scientific facts from reputable sources and industry-wide safety practices, as seen below:
I am not saying you cannot dive to 60m on air. I am telling you that if you think its safer than on Tx, you are seriously mistaken.
For more info on gas density, CO2 retention, WOB and narcosis (things @mac64 is subjectively immune to) please refer here: Alert Diver | Performance Under Pressure
Some important excerpts:
Figure 1 shows the proportion of rebreather test dives ending in failure due to an end-tidal CO2 > 8.5 kPa (top section of bars) and other causes of failure (middle section of bars) stratified by respired gas density. The numbers in the bars refer to the number of dives. At respired gas densities >6 g/L–1, there is a sharp increase in the risk of dive failure, with most failures being caused by dangerous levels of CO2 retention.
Helium appears to be the immediate solution for divers who are concerned about WOB and correlated medical issues (immersion pulmonary edema, CO2 retention, etc.) and for technical divers who are doing even normal dives to moderate depths. Seven times less dense than nitrogen, helium also ameliorates the severity of narcosis but brings with it a host of new obstacles, including extended decompression, cost and high-pressure neurological syndrome (HPNS) concerns.
If you want to know more about why even on OC the gas density is an issue, take a look at this video:
The gas density is WOB and CO2 retention issue not because of the limits of OC/CCR, but due to the way, your lungs are built.
Be smart and keep an open mind to learning new things from reputable sources.
Considering this is a deco dive, the lack of safety reserve and many other aspects is alarming. Have you ever heard of lost gas / +5min / +5m planning and procedures? Are you even certified below 40m or is it just another piece of paper you do not need?
Congratulations, keep trying. With your attitude, you will get there.
So hard working/overexertion is always preventable? Congratulations, you are probably the only diver in the world who can be sure about that.
So aside from hyperbaric physiologist, you are also a material engineer? I hope that you do not fill untested tanks. But honestly/sadly, it would not surprise me.
I am not saying you cannot dive to 60m on air. I am telling you that if you think its safer than on Tx, you are seriously mistaken.
Air at 60m is about 8.5g/l. You might not notice it as the change is gradual and you are significantly narced in the end, but the gas density is in dangerous levels. But unless you try to switch to trimix at that depth to see the difference, there is no point discussing this with you are you have absolutely no clue what you are talking about.
You can discuss subjectivity of nitrogen narcosis and effects of WOB at 40m (bordeline). Not in 60m. Again, you just do not know how much you do not know / how narced in fact you are.
Again, Air at 60 is about 8.5g/l. Please see the table below to see how even 6-7g/l is dangerous.
Maybe with nitrogen. If you get CO2 hit from hard work at 60m, you are pretty much ******.
For more info on gas density, CO2 retention, WOB and narcosis (things @mac64 is subjectively immune to) please refer here: Alert Diver | Performance Under Pressure
Some important excerpts:
Figure 1 shows the proportion of rebreather test dives ending in failure due to an end-tidal CO2 > 8.5 kPa (top section of bars) and other causes of failure (middle section of bars) stratified by respired gas density. The numbers in the bars refer to the number of dives. At respired gas densities >6 g/L–1, there is a sharp increase in the risk of dive failure, with most failures being caused by dangerous levels of CO2 retention.
Helium appears to be the immediate solution for divers who are concerned about WOB and correlated medical issues (immersion pulmonary edema, CO2 retention, etc.) and for technical divers who are doing even normal dives to moderate depths. Seven times less dense than nitrogen, helium also ameliorates the severity of narcosis but brings with it a host of new obstacles, including extended decompression, cost and high-pressure neurological syndrome (HPNS) concerns.
If you want to know more about why even on OC the gas density is an issue, take a look at this video:
The gas density is WOB and CO2 retention issue not because of the limits of OC/CCR, but due to the way, your lungs are built.
Be smart and keep an open mind to learning new things from reputable sources.
I think the problem is, that Mac´s definition of "best" is off.
IMHO air is never the best gas for any dive. If it is shallow Nitrox is better, if it´s depper, trimix will be better, for deco, Nitrox/O2 will be better.
However, it might be the case that air is more "convenient" or that the best solution is simply not available so you go for a compromise.
The key question then, that everyone has to answer for himself is, how he factors convenience and safety. I personally do this by asking myself how the margin for recovering in case of trouble is vs. how the outcome would be if the s*** hits the fan.
Of course by training, experience and adaption you can mitigate risk, but you will always have some risk left, that you cant account for.
IMHO air is never the best gas for any dive. If it is shallow Nitrox is better, if it´s depper, trimix will be better, for deco, Nitrox/O2 will be better.
However, it might be the case that air is more "convenient" or that the best solution is simply not available so you go for a compromise.
The key question then, that everyone has to answer for himself is, how he factors convenience and safety. I personally do this by asking myself how the margin for recovering in case of trouble is vs. how the outcome would be if the s*** hits the fan.
Of course by training, experience and adaption you can mitigate risk, but you will always have some risk left, that you cant account for.
25min bottom time @ 60m on air and backgas deco - runtimes:
GF 30/70: 166 min
GF 40/80: 134 min
GF 50/90: 110 min
GF 60/100: 93 min
GF 80/100: 89 min
GF 100/100: 86 min
GF 100/110: 77 min -> this profile looks like what he described
Also, for 40-50bar remaining from 300bar fill is about 26L/min SAC for the bottom portion of the dive.
I'll let you be the judge of mac64's safety margins....
PS: Last few posts edited to only play the ball
A ScubaBoard Staff Message...
Readers are trusted to be wise and responsible enough to make their own decisions without the need for brow beating by those that believe theirs is the only safe way to dive. Going forward, posts that contain these types of attacks will be deleted in their entirety and the relevant info can be reposted without the references to chest thumping, "this guy" and other labels used to describe our members. We are all here because we love diving and none of us has it all figured out. We have years of examples of people that lecture others on their practices only to get bent themselves later. We should support each other but failing that, we should not beat each other up. Thanks for your participation. I'm asking for an adjustment, that is all.
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