#1 Rule In Scuba, Don't Hold Your.....

[blac86]

Everything taught in OW is taught because OW divers are like challenged children who's only goal in life is to kill themselves. In reality every rule you learned: No Deco Limits, Air is toxic below 189ft, air is toxic above a ppo2 of 1.6, don't hold your breath, always dive with a buddy, don't exceed your experience, all of it is gross oversimplification of safety protocols taught in that manner because OW divers can't be trusted not to try and die.

I regularly do deco, breathe air to 210ft, have seen someone in a chamber on a ppo2 of 2.4, freedive, hold my breath during reg exchanges and solo dive. And still the only incident I've experienced was a mechanical failure of a second stage.

 

[rob.mwpropane]

Absolutely NOT possible. Not remotely possible. You can't make noise with your vocal chords if air is not passing over and they comprise the seal of the glottis. You can clap or snap your fingers, but if you're humming, making an ahhhh or eeeeeee sound, then the glottis is open. It has to be.

Like I said, I can't do it and make a sound, but again I think it's neither here nor there?

Everything taught in OW is taught because OW divers are like challenged children who's only goal in life is to kill themselves.

This I found very funny, and the rest of your post was very informative.

I get that there's people that just want to learn something, be able to say they can do it, get the certification and move on (there's nothing wrong with that). I've never been one of those people. I like to know something, not just learn it. I have a need to know why things are, hence I usually find myself cruising an internet forum searching for answers.

 

[The Chairman]

This I found very funny, and the rest of your post was very informative.

Young or old, I treat my students like they actually want to learn. We have an extensive discussion about the glottis and how to keep it open at all times. OW students also learn how to take a super-breath without holding it in order to truly master buoyancy before the end of the class.

As a caveat, there is a story of an instructor candidate during their IDC in Miami debating about how deadly holding your breath can be. To prove his instructor trainers wrong, he took a deep breath at the bottom of the pool and surfaced. He embolized, went into a coma and never woke up. There's nothing down there worth dying or even getting hurt over. Physiology and physics won't make an exception for you.

 

[boulderjohn]

I regularly do deco, breathe air to 210ft, have seen someone in a chamber on a ppo2 of 2.4, freedive, hold my breath during reg exchanges and solo dive. And still the only incident I've experienced was a mechanical failure of a second stage.

And lots of people drive drunk and have been OK so far. Does that make it a good idea?

In many of the cases you describe, it is not a matter of a black and white matter of "here you are OK; go over that line and you die." It is a matter of determining probabilities and deciding where to draw the line where the risk becomes too great. Here are some examples.

• Oxygen toxicity under water will kill you. It is caused by breathing too high a concentration of O2 for too long a period of time. What is too much? What is too long? It seems to vary by the individual and the incident. Standards for a safe PPO2 have been created because we are sure people are safe at those depths and those times. We are not so sure beyond those limits. It is not like you will die if you exceed your MOD for a few minutes; but you are not guaranteed to be safe, either.
• Exceeding a certain depth on air is unsafe because of two reasons--oxygen toxicity (mentioned above) and narcosis. Narcosis is very uncertain and unpredictable. Many people have gone deep on air and been fine. Others not so much. Chris and Chrissy Rouse dived to 230 feet on air, and the narcosis led them to make very bad decisions that got them killed. Opal Cohen and friends decided to do a bounce dive to 300 feet on air. When they reached 300 feet, she was so narced she kept going down. Her friend and DM went after her and turned her around. They did not have enough gas to do decompression. She died. He will never walk again.
• No decompression limits are where we are very sure that all but a tiny percentage of the population will be safe. Violate those limits by a minute or two and you will still probably be OK, but the odds are starting to go against it. The more you violate the limits, the more likely you are to have a problem. You could ask Chris Rouse, Chrissy Rouse, or Opal Cohen (mentioned above) about that if they were still alive.

So, in all cases, it is a matter of rolling the dice. There is a good chance you will be OK. There is a chance you will not. The more you push the limit, the more likely it will be that you will not be OK. It all comes down to one question--how lucky do you feel today?

And BTW, the Navy stopped testing people's ability to withstand oxygen toxicity in the chamber years ago, when they realized that for reasons that are not well understood, people can endure much greater PPO2s in a chamber than they can under water.

 

[Saboteur]

I

Absolutely NOT possible. Not remotely possible. You can't make noise with your vocal chords if air is not passing over and they comprise the seal of the glottis. You can clap or snap your fingers, but if you're humming, making an ahhhh or eeeeeee sound, then the glottis is open. It has to be.

Interesting. I practiced 3-4 pool CESA with a DM last week. The first two done making the "ahhh" sound and blowing a constant stream of bubbles through the reg resulted in emptying the lungs too soon to complete the distance. The third attempt I just tried making the "ahhhh" sound deep in the throat without bubbles being exhausted, which was commented on by the DM that he couldn't see bubbles, but could hear it. Maybe air was being exhaled via nasal passages and mask which was not evident. In any case it was easier.... but would doing that be safe?

 

[Neilwood]

Everything taught in OW is taught because OW divers are like challenged children who's only goal in life is to kill themselves. In reality every rule you learned: No Deco Limits, Air is toxic below 189ft, air is toxic above a ppo2 of 1.6, don't hold your breath, always dive with a buddy, don't exceed your experience, all of it is gross oversimplification of safety protocols taught in that manner because OW divers can't be trusted not to try and die.

I regularly do deco, breathe air to 210ft, have seen someone in a chamber on a ppo2 of 2.4, freedive, hold my breath during reg exchanges and solo dive. And still the only incident I've experienced was a mechanical failure of a second stage.

I think the analogy is more like driving.

Most drivers will learn the basics of what a steering wheel, accelerator etc do and never use it on anything but the high way sticking to predetermined speeds and roads. For the vast majority of people the rules are fine, they are pretty safe and they have no need or desire to push them.

With more training and practise, some drivers want to go off-roading (caving, wrecks), go on faster roads or race (deep or longer). They do so in the knowledge that they need to be more careful when pushing harder.

Taking your examples:
1) You don't do deco unless you know you have the air to do it by careful gas planning
2) air to 210ft is really not a great idea (doable but you will almost guaranteed to be very noticeably narced)
3) PP O2 of 2.4 is ok in specific circumstances for short periods under supervision such as in a chamber and even then air breaks are normally included
4) holding breath while exchanging regs is ok so long as you can maintain depth
5) Solo diving is ok so long as you know what you are doing and have redundant equipment that you can use or have a plan in place for failures such as diving conservatively and being able to bail to the surface at all times.

Those examples are all example of things that have killed people in the past but can be mitigated with the appropriate steps (which are not generally suitable for teaching to new divers).

 

[rob.mwpropane]

And lots of people drive drunk and have been OK so far. Does that make it a good idea?

In many of the cases you describe, it is not a matter of a black and white matter of "here you are OK; go over that line and you die." It is a matter of determining probabilities and deciding where to draw the line where the risk becomes too great. Here are some examples.

• Oxygen toxicity under water will kill you. It is caused by breathing too high a concentration of O2 for too long a period of time. What is too much? What is too long? It seems to vary by the individual and the incident. Standards for a safe PPO2 have been created because we are sure people are safe at those depths and those times. We are not so sure beyond those limits. It is not like you will die if you exceed your MOD for a few minutes; but you are not guaranteed to be safe, either.
• Exceeding a certain depth on air is unsafe because of two reasons--oxygen toxicity (mentioned above) and narcosis. Narcosis is very uncertain and unpredictable. Many people have gone deep on air and been fine. Others not so much. Chris and Chrissy Rouse dived to 230 feet on air, and the narcosis led them to make very bad decisions that got them killed. Opal Cohen and friends decided to do a bounce dive to 300 feet on air. When they reached 300 feet, she was so narced she kept going down. Her friend and DM went after her and turned her around. They did not have enough gas to do decompression. She died. He will never walk again.
• No decompression limits are where we are very sure that all but a tiny percentage of the population will be safe. Violate those limits by a minute or two and you will still probably be OK, but the odds are starting to go against it. The more you violate the limits, the more likely you are to have a problem. You could ask Chris Rouse, Chrissy Rouse, or Opal Cohen (mentioned above) about that if they were still alive.

So, in all cases, it is a matter of rolling the dice. There is a good chance you will be OK. There is a chance you will not. The more you push the limit, the more likely it will be that you will not be OK. It all comes down to one question--how lucky do you feel today?

And BTW, the Navy stopped testing people's ability to withstand oxygen toxicity in the chamber years ago, when they realized that for reasons that are not well understood, people can endure much greater PPO2s in a chamber than they can under water.

Very informative also. I'm by no means going to break any "rules", and have no intention to. I will admit I like a good discussion talking about the grey areas just for knowledge gained.

I don't drink at all, doesn't mean I'm not fascinated by the effects it has on the human brain...

 

[blac86]

And lots of people drive drunk and have been OK so far. Does that make it a good idea?

In many of the cases you describe, it is not a matter of a black and white matter of "here you are OK; go over that line and you die." It is a matter of determining probabilities and deciding where to draw the line where the risk becomes too great. Here are some examples.

• Oxygen toxicity under water will kill you. It is caused by breathing too high a concentration of O2 for too long a period of time. What is too much? What is too long? It seems to vary by the individual and the incident. Standards for a safe PPO2 have been created because we are sure people are safe at those depths and those times. We are not so sure beyond those limits. It is not like you will die if you exceed your MOD for a few minutes; but you are not guaranteed to be safe, either.
• Exceeding a certain depth on air is unsafe because of two reasons--oxygen toxicity (mentioned above) and narcosis. Narcosis is very uncertain and unpredictable. Many people have gone deep on air and been fine. Others not so much. Chris and Chrissy Rouse dived to 230 feet on air, and the narcosis led them to make very bad decisions that got them killed. Opal Cohen and friends decided to do a bounce dive to 300 feet on air. When they reached 300 feet, she was so narced she kept going down. Her friend and DM went after her and turned her around. They did not have enough gas to do decompression. She died. He will never walk again.
• No decompression limits are where we are very sure that all but a tiny percentage of the population will be safe. Violate those limits by a minute or two and you will still probably be OK, but the odds are starting to go against it. The more you violate the limits, the more likely you are to have a problem. You could ask Chris Rouse, Chrissy Rouse, or Opal Cohen (mentioned above) about that if they were still alive.

So, in all cases, it is a matter of rolling the dice. There is a good chance you will be OK. There is a chance you will not. The more you push the limit, the more likely it will be that you will not be OK. It all comes down to one question--how lucky do you feel today?

And BTW, the Navy stopped testing people's ability to withstand oxygen toxicity in the chamber years ago, when they realized that for reasons that are not well understood, people can endure much greater PPO2s in a chamber than they can under water.

Please don't misunderstand I'm not advocating for flippant violation of safety protocols, simply stating that ever rule learned in open water isn't really a rule and with proper execution many "unsafe" things are perfectly safe.

 

[The Chairman]

In any case it was easier.... but would doing that be safe?

If you're making ANY noise, your glottis is open. You'll find making a consonant noise like an M or N uses far less air. Stick your tongue up on the roof of your mouth and the air will flow through your nose... but it will still flow.

You should learn glottis control without having to make a noise. Americans don't use a glottal stop (how Ringo says "Bottle"), but we do use a glottal fricative: the "H". Of course, all voiced vowels and consonants use the glottis, but it's so automatic that you don't even notice it. You do use your glottis when you cough, so that might be the best way to learn to control it. Any pause of your breathing cycle should be done with the glottis W-I-D-E open. Use your chest muscles and diaphragm to accomplish this and not your mouth, glottis or epiglottis (back of your tongue).

 

[Neilwood]

Please don't misunderstand I'm not advocating for flippant violation of safety protocols, simply stating that ever rule learned in open water isn't really a rule and with proper execution many "unsafe" things are perfectly safe.

It would have been worth stating the proviso for additional training and experience within your original post as a new diver reading your post in isolation might take it those actions are safe.