When I was a kid in the 70s, I think the record was somewhere in the neighborhood of 3–5 minutes (maybe seven?) and we used to think that was such a short time that we could do it and then trying in the backyard bucket pools that were endemic in my neighborhood we found that cracking a minute was enough of a challenge.
Such contests are more dangerous than they first appear: Many kids will grasp the obvious trick of hyperventilating to improve their time, but that can lead to abrupt unconsciousness and drowning.
I imagine a safe version could be made... that would suck all the direct-competition spontaneity out of it. Like "do it on land", or "only in standing-height water and take turns with someone timing and acting as a spotter."
As a teenager I did about 4.5 minutes, as I recall, in a bucket of water. I played the trumpet quite a bit at the time, so I think my capacity was above average. It was a competition and I got first, and the second place fellow was also a trumpet player.
All three of us trumpet players in my middle school band would sit in the back and have breath holding contests while the director was working with other sections or whatever.
In middle school, I was a swimmer on two teams and played trombone. We had a fun little “who can play the longest note” contest…everyone thought I cheated because I lasted about 30 seconds longer than anyone else. Really wasn’t that hard once you find the right position to use minimal air output, since the game wasn’t who could hold the same note, but any note. We regularly trained on the swim team to go as far as possible underwater in an Olympic pool — record on our team was 4 or 5 round-trips if I recall correctly (can’t remember 100%…long ago…but that kid was crazy in both speed and time underwater).
Pretty demoralizing to be labeled a cheater after such hard work expanding lung capacity and efficiency. After that, I wouldn’t even try anymore just so I wouldn’t be called a cheater again. Quit band the next year.
It should given that it works with trumpet (and even voice). I remember listening to some jazz piece on the radio where the DJ, before the song, alerted listeners to the long note that was being held and suggested trying holding your breath for the length of the note (but not—he warned—if you were driving).
It would, which was exactly what I was accused of but wasn’t something I knew how to do…even to this day. I have an idea of the mechanics, I just lack the ability because it has never been something I’ve practiced or developed.
I once held my breath for 5 minutes when I was 14, sitting in class. I suppose it’s possible I was accidentally breathing through my nose a little as I wasn’t underwater.
My brother did this in his geometry class and passed out. The nurse called my mom and asked if they should send him home to which she responded, “hell, no!”
From my experience, holding your breath in air and in water are totally different things. I guess, because it is difficult to stop any intake of air when you are in air.
Amazingly so Stephane Mifsud's 11:35 "regular air" WR apnea was set in 2009 and has stood since (at least as far as AIDA is concerned). There was a lot of speculation online back then as it is an extraordinary time and was quite high compared to the previous record. If I recall correctly the hold was performed at his home pool, and he has a lung capacity almost double the average adult male's.
This is a video of the end of Mifsud's 11:35 breath hold: https://www.youtube.com/watch?v=MHPGKb7ipgc . The protocol after the hold is that you have to take off your goggles/mask and noseclip, look at the judges and do a clear hand signal that you're ok. Your chin/face should not touch the water before you get a reply from the judges, in the form of a card. It's nothing short of amazing how clearly he follows protocol given that his brain has been oxygen deprived for more than 11 minutes.
We train for surface protocol to become automatic, so even depraved of oxygen, it becomes a reflex. It does a big difference, you'd be surprised to see how many ppl blackout when surfacing because they exhale too much first :/
Regarding Mifsud, he had a YouTube channel, in French, which is full of information about freediving ! He worked a lot with scientists to understand how his body work and how to reach this world record.
Also he confessed that he does not have spams when holding breath, so it helps a bit.
I somehow thought that pure oxygen was poisonous[1], and it needed to be a nitrogen mix. I mean, I guess this stunt demonstrates that I'm clearly mistaken, or that the nuance is in the pressures involed?
Pure oxygen puts oxidative stress on your cells. Your body can handle that just fine at 1 atm, but at elevated partial pressures the increased concentration will (quickly) overwhelm your cellular mechanics.
Underwater, the maximum operating depth for 100% O2 is 6 meters (20 feet) - which isn't very much at all. If you dive any deeper than that, you'll be at severe risk for a seizure and unconsciousness, and likely drown. (I'm simplifying, see [1].)
Which is why you don't go diving with pure O2.
However, in this case the freediver wouldn't be breathing compressed O2 gas underwater. They would've been breathing it at the surface, at 1 atm.
Oxygen weathering is a primary constraint on life on Earth, and every carbon-hydrogen based organism in the past 2.5 billion years has had to develop biochemical coping mechanisms for this toxic gas that wants to react with carbon and with hydrogen; It is harnessing this reaction ("respiration") with biologically mediated processes and modulating it to specific rates that permits us life.
For humans, acute breathing gas toxicity only happens in a high pressure environment.
Air approximates an 80/20 nitrogen-oxygen mix. Atmospheric pressure is 14.7psi.
The 120psi air compressor in your auto body shop is equivalent to a dive only 81 meters deep. SCUBA divers and later saturation divers have probed the various limits of the human cardiopulmonary system using very specialized gas blends all the way down to 700 meters. Too much oxygen partial pressure causes all the symptoms you see listed, and higher partial pressures cause symptoms to appear faster.
> The curves show typical decrement in lung vital capacity when breathing oxygen. Lambertsen concluded in 1987 that 0.5 bar (50 kPa) could be tolerated indefinitely.
This means you could breath 80/20 nitrox at 2.5 bar, or 37 psi, or 25 meters depth, "indefinitely" in the sense of hours or days.
PS: Chronic use of 100% oxygen at atmospheric pressure causes other types of toxicity. Some of the oxidative damage therein, accumulated over the years at a normal 20%, probably directly analogizes parts of the human aging process. Other types of oxidative damage probably work faster than proportional exposure. We only start to notice damage like this in people with impaired lung function who rely on an artificial supply of oxygen boosted to beyond an 80/20 ratio, to breath.
To add to this, when diving with compressed air most people get woozy and otherwise intoxicated from oxygen around 30 meters from the surface. For some people 25 meters is enough for such symptoms to occur.
Yes, he is. Oxygen toxicity causes seizures, not narcosis, and kicks in at around 1.6 bar of partial pressure (just below 65 m when breathing 21% oxygen as in regular air). PADI uses 1.4 bar to add an extra safety margin.
Oxygen toxicity is really the one thing in recreational diving that will kill you if you do it wrong, though for recreational divers the risk only exists when using enriched air(*).
Fortunately it's trivial to avoid it by only using enriched air where the sea floor is at a safe depth, but you should know the math nevertheless. For example if the sea floor is at 35 m (4.5 bar) you won't enrich air above 1.4/4.5=31% oxygen, probably more like 28%.
Oxygen toxicity is also the (or the main) reason why enriched air must never be stored in white or yellow bottles. If you see yellow you can assume it's 21%, while for any other color you must use an oxymeter before using it. Not doing so can be literally the difference between life and death.
Scuba diving is safe but a lot of the safety is about procedures, as you can see.
(*) Enriching air above 21% oxygen is done to avoid the other issue with nitrogen, which is decompression sickness. It lets you stay longer on the bottom. In other words, enriched air improves the trade-off between bottom time (limited by nitrogen) and maximum depth (limited by oxygen toxicity).
Not with 21% oxygen. 25 meters is 3.5*0.21=0.73 bar of O2 partial pressure, which is within even the strictest limits that apply to rebreathers (1.3 bar).
If you're breathing 100% oxygen for decompression, that's a completely different story and not something a recreational divers will do.
I don't see any thing that supports "when diving with compressed air most people get woozy and otherwise intoxicated from oxygen around 30 meters from the surface".
"Be aware that oxygen toxicity is unpredictable. Divers have experienced convulsions at shallow depths under conditions where most experts would not have expected them to occur."
But that doesn't say what depth, what oxygen % and how often it happens.
It also says that oxygen toxicity is a possibility only above 21% oxygen. In fact, with regular air there are way too many things that have already gone wrong if you are at 65 m depth (or even 50 m).
It's clear from reading the document that convulsions at "shallow depths" refers to the case of breathing 100% oxygen, where 1.5 m difference is the difference between <1.6 bar (safe) and >1.7 bar (absolutely not safe).
700m! That's wild, I mean nuclear submarine crush depths are at like 400-500m? I get that it's not like you can compare a hard steel tube with a human body but regardless, it's wild.
The published data for military submarines is the nominal test depth, not the actual design limit. The operational depth may be much deeper but that will be classified.
Recent US submarines all have test depths described by as being in excess of the same few hundred meters. In all likelihood that is a throwaway value. It seems unlikely that they produced generations of submarines that were less capable than their older ones.
> The published data for military submarines is the nominal test depth, not the actual design limit. The operational depth may be much deeper but that will be classified.
We know the actual collapse depth for an older sub: 730m for the USS Thresher (test depth: 400m), in 1963.
Test depths of current generation subs are ~20% higher; pushing them to 700m or so might be plausible, but not much more. Radical hidden capabilities would either require substantial advances in material science or drastically different hull thickness, neither of which is really feasible to hide from adversaries anyway, especially considering how little utility you get from hiding this (compared to e.g. exact capabilities of anti-air interceptors or radar characteristics for bombers/fighters).
There are of course vessels that have gone deeper and are specially designed for it, but it struck me that the depth specified was close to that of 'standard' subs that are not specially designed for very deep operations
>It seems unlikely that they produced generations of submarines that were less capable than their older ones.
i wouldn't be sure. There seems to be no military advantage to deeper so why spend the money. A sub needs to hide, but it can't do any other job when too deep. sinking ships can only be done when near the surface. If the sub can get under a couple thermo layers that is good enough, any deeper is more a party trick than useful.
i'm not in the navy but that is how I read the unclassified information I have access to.
> sinking ships can only be done when near the surface.
Isn't this itself a huge assumption?
Sinking ships via upward facing torpedoes would be a huge tactical advantage at first glance. Less time to detection and deploy countermeasures or evasive maneuvers.
Perhaps, I am wrong in assuming they cannot be fired below a certain depth?
Indeed, the grandparent post is a pretty good summary of the takeaways you get from taking PADI’s enriched air nitrox course (which is a requirement if you ever want to dive with enriched air).
In the olden days this was tracked manually (the ratio of your depth to percentage of air and time under water) via so called “dive tables”. The purpose and output of the dive table is to determine the safe amount of time you could dive at a certain depth without risking narcosis.
As this is a sliding window based on multiple variables - and you are very rarely maintaining a constant depth as you dive - it’s of course annoying and less accurate to hand calculate this. Modern dive computers just seamlessly calculate it all for you nowadays.
Fun fact: those dive tables were created by the US Navy conducting experiments on its own divers, there was a real human cost to acquire that information.
Scuba diving is great. You don't have to do deep or risky dives to enjoy it. There's a ton of fun in diving around reefs 10m down.
That story is pretty wild. And relatable.
I got myself into a little trouble when I dove the Blue Hole 16 years ago. We were warned pretty heavily how many people have died doing it, so I went in with a healthy level of anxiety. It was my second dive where the dive plan was to go to 40m, which is the limit on regular air.
The descent was surreal. You have the wall of the crater on your side, but everything else is different shades of blue. Past about 10m, there's not really any wildlife to look at, just blue. We descended straight down, going in slow motion. As we went down the blues got gradually darker and deeper.
At probably the high 20s, I started to notice I could really see the surface clearly anymore, and I started to panic. My breath started racing and I started being annoyed by my regulator in my mouth, which is an unnatural feeling to being with. For maybe a minute, I debated whether I should try to get myself under control, or signal my dive instructor I wanted to ascend. Meanwhile, we were still drifting downward. I worried whether nitrogen narcosis might affect my judgment or ability to control my panic.
In the end, I decided not to be a hero. I gave my instructor the thumbs up to ascend, and we went through the orderly process of safety stops. When we got to the top I told her I explained I was feeling panicky (you can't really communicate anything nuanced below the surface), and then I spent the rest of my tank diving the first 10m, which was relaxing, and let me finish the day on a high note.
that comment is a classic and certainly entertaining, but there are multiple levels of safety to prevent something like this from happening, the first of which is the wall of tombstones that greets you when you arrive at that specific dive site. To end up in that situation means to have already made a number of big, big errors.
I remember the Blue Hole as one the best dives I made, and not even the scariest: that prize goes to the time I was in calm waters at 20 meters, and the pressure regulator just failed, leaving me without air from both mouthpieces. And that's why you have a buddy...
I don't think I've ever had anything fail on me diving, but I've been with people who have run out of air (my buddy was constantly using all his up), so having to breathe off someone else's tank isn't uncommon.
As I mentioned in my sibling comment, I did have a scary time on the Blue Hole. I think my other most nervous dives were:
- Pacific dive in Costa Rica in rough seas and surge. We suddenly had visibility drop to near zero when we hit the outflow current of a river. Definitely a lesson in how quick conditions can change.
- Cavern diving in a cenote in Mexico. Nothing weird happened, but we went kinda far in, and I get nervous in overhead environments.
Running out of gas or having to breathe off of someone else's tank is uncommon. Gas planning and monitoring is a fundamental skill that every diver needs to master just to get a basic open water certification. If your buddies aren't able to do this reliably then they need remedial training.
It's good to practice gas sharing as a contingency in case of equipment failure but actually running out is not acceptable.
same, blue hole is notorious because inexperienced divers get pressured into deep dives they haven't trained for by local guides looking to make a quick buck.
my scariest dive was when a 14 year old got separated from the group and thought it would be a good idea to continue his dive for 30 minutes.
It’s really several factors. Supplemental oxygen is common for people with diminished lung capacity, carbon monoxide exposure etc. However long term it’s not a good idea for healthy people. https://en.wikipedia.org/wiki/Oxygen_therapy
At low pressure pure oxygen can similarly be beneficial, mountain climbers eventually need supplemental oxygen for Mount Everest though a few have made the trip without it they can’t stay at that altitude indefinitely. It can even help on airplane flights as commercial airlines don’t set things to sea level.
Where healthy people run into issues is when partial pressures get well over 100% at sea level. Part of the issue is people adjust their breathing based on carbon dioxide not oxygen levels. So at say 10 atmospheres at normal atmospheric mixtures your breathing the equivalent of 210%, but you don’t slow down enough to compensate. Thus why divers care so much about gas mixtures, however people with diminished lung capacity are going to encounter issues at different levels than normal divers.
Yes, partial pressure is what matters. Normal air at 1 bar (1 atmosphere) contains about 0.2 bar of O2. Pure oxygen at sea level is 1 bar of O2.
The article you linked has a graph showing that 0.5 bar of O2 can be tolerated pretty much indefinitely, and it takes hours for significant toxicity to show up at 1 bar. Higher partial pressures cause much faster symptoms.
It is, kinda sorta, but at 1 atm you need to be breathing pure o2 for ~24 hrs before its meaningful (and longer than that before treatment is anything beyond "stop breathing pure o2". The dose isn't even cumulative. Just being on room air for 20-30 minutes resets the clock.
How is it even possible to hold breath for 11 minutes? I tried it last week (to avoid inhaling insecticide fumes) and could manage about a minute after trying very hard.
Genetics/randomness must play a significant role. When I was a teenager I could hold my breath for ~1.5 minutes without even trying. With a bit of technique I got it up to 2 minutes with relative ease, I think my max was around 2.5 minutes. The odd thing is that I had no reason to be able to do that, I was pretty out of shape, I didn't play any instruments, or have any other hobbies that would help build that kind of stamina.
On the flip side, out of all the genetic benefits one can get, this might be the lamest one. :(
I'm rather unfit these days - but as a teen I could easily do 3mins at my desk in a class. I can't remember the volume but we did a lung capacity test at school and I had the highest in the class, despite not being sporty or active at all, so I think I have genetics on my side.
I recently tried the 'Wim Hof' method, and was well over 4mins after just a few days practice, and I just went snorkelling and was able to outlast all those I went with. If I was healthier I am sure I could get longer still.
When I was a kid in the 70s, I think the record was somewhere in the neighborhood of 3–5 minutes (maybe seven?) and we used to think that was such a short time that we could do it and then trying in the backyard bucket pools that were endemic in my neighborhood we found that cracking a minute was enough of a challenge.
At first.
I was also a kid doing this, my cousins and I held ourselves underwater with the ladder rungs in a swimming pool.
At first, yeah a minute was tough. But then it rapidly increased. Unfortunately I don't remember where we topped out, but I think ~3 minutes.
We would also swim pool lengths underwater(but it was a relatively small pool at a condo building). I think I swam 9 once.
They'd let us stay out all night at that pool, it was great. Florida summers don't really get chilly.
Such contests are more dangerous than they first appear: Many kids will grasp the obvious trick of hyperventilating to improve their time, but that can lead to abrupt unconsciousness and drowning.
https://en.wikipedia.org/wiki/Shallow-water_blackout
I know that now, and I would prevent any kids from breath-holding contests.
But I didn't at 14 years old, nor did my mom or uncle, apparently.
I imagine a safe version could be made... that would suck all the direct-competition spontaneity out of it. Like "do it on land", or "only in standing-height water and take turns with someone timing and acting as a spotter."
Yes, although as another commenter pointed out, being underwater triggers a response in our body that lowers our oxygen consumption.
We did spot for each other, even then, but I don't ever remember anyone thinking they almost passed out or anything.
Funny, I did exactly the same things in my childhood, in my cousin's pool.
But it was on the other side of the pond!
As a teenager I did about 4.5 minutes, as I recall, in a bucket of water. I played the trumpet quite a bit at the time, so I think my capacity was above average. It was a competition and I got first, and the second place fellow was also a trumpet player.
All three of us trumpet players in my middle school band would sit in the back and have breath holding contests while the director was working with other sections or whatever.
In middle school, I was a swimmer on two teams and played trombone. We had a fun little “who can play the longest note” contest…everyone thought I cheated because I lasted about 30 seconds longer than anyone else. Really wasn’t that hard once you find the right position to use minimal air output, since the game wasn’t who could hold the same note, but any note. We regularly trained on the swim team to go as far as possible underwater in an Olympic pool — record on our team was 4 or 5 round-trips if I recall correctly (can’t remember 100%…long ago…but that kid was crazy in both speed and time underwater).
Pretty demoralizing to be labeled a cheater after such hard work expanding lung capacity and efficiency. After that, I wouldn’t even try anymore just so I wouldn’t be called a cheater again. Quit band the next year.
I wonder if circular breathing would work, or works, for trombone. If so you could have held that note "forever" with some training.
It should given that it works with trumpet (and even voice). I remember listening to some jazz piece on the radio where the DJ, before the song, alerted listeners to the long note that was being held and suggested trying holding your breath for the length of the note (but not—he warned—if you were driving).
It would, which was exactly what I was accused of but wasn’t something I knew how to do…even to this day. I have an idea of the mechanics, I just lack the ability because it has never been something I’ve practiced or developed.
I could do 3 minutes pretty easily as a kid, again, sitting in class like another poster. Maybe we had the same boring classes.
I once held my breath for 5 minutes when I was 14, sitting in class. I suppose it’s possible I was accidentally breathing through my nose a little as I wasn’t underwater.
Glad I'm not the only one who was bored enough in class to do this.
It was Latin...
My brother did this in his geometry class and passed out. The nurse called my mom and asked if they should send him home to which she responded, “hell, no!”
From my experience, holding your breath in air and in water are totally different things. I guess, because it is difficult to stop any intake of air when you are in air.
¯\_(ツ)_/¯
Amazingly so Stephane Mifsud's 11:35 "regular air" WR apnea was set in 2009 and has stood since (at least as far as AIDA is concerned). There was a lot of speculation online back then as it is an extraordinary time and was quite high compared to the previous record. If I recall correctly the hold was performed at his home pool, and he has a lung capacity almost double the average adult male's.
This is a video of the end of Mifsud's 11:35 breath hold: https://www.youtube.com/watch?v=MHPGKb7ipgc . The protocol after the hold is that you have to take off your goggles/mask and noseclip, look at the judges and do a clear hand signal that you're ok. Your chin/face should not touch the water before you get a reply from the judges, in the form of a card. It's nothing short of amazing how clearly he follows protocol given that his brain has been oxygen deprived for more than 11 minutes.
We train for surface protocol to become automatic, so even depraved of oxygen, it becomes a reflex. It does a big difference, you'd be surprised to see how many ppl blackout when surfacing because they exhale too much first :/
Regarding Mifsud, he had a YouTube channel, in French, which is full of information about freediving ! He worked a lot with scientists to understand how his body work and how to reach this world record. Also he confessed that he does not have spams when holding breath, so it helps a bit.
I somehow thought that pure oxygen was poisonous[1], and it needed to be a nitrogen mix. I mean, I guess this stunt demonstrates that I'm clearly mistaken, or that the nuance is in the pressures involed?
1: https://en.wikipedia.org/wiki/Oxygen_toxicity
There's definitely nuance here.
Pure oxygen puts oxidative stress on your cells. Your body can handle that just fine at 1 atm, but at elevated partial pressures the increased concentration will (quickly) overwhelm your cellular mechanics.
Underwater, the maximum operating depth for 100% O2 is 6 meters (20 feet) - which isn't very much at all. If you dive any deeper than that, you'll be at severe risk for a seizure and unconsciousness, and likely drown. (I'm simplifying, see [1].)
Which is why you don't go diving with pure O2.
However, in this case the freediver wouldn't be breathing compressed O2 gas underwater. They would've been breathing it at the surface, at 1 atm.
[1]: https://en.wikipedia.org/wiki/Maximum_operating_depth
Oxygen weathering is a primary constraint on life on Earth, and every carbon-hydrogen based organism in the past 2.5 billion years has had to develop biochemical coping mechanisms for this toxic gas that wants to react with carbon and with hydrogen; It is harnessing this reaction ("respiration") with biologically mediated processes and modulating it to specific rates that permits us life.
For humans, acute breathing gas toxicity only happens in a high pressure environment.
Air approximates an 80/20 nitrogen-oxygen mix. Atmospheric pressure is 14.7psi.
The 120psi air compressor in your auto body shop is equivalent to a dive only 81 meters deep. SCUBA divers and later saturation divers have probed the various limits of the human cardiopulmonary system using very specialized gas blends all the way down to 700 meters. Too much oxygen partial pressure causes all the symptoms you see listed, and higher partial pressures cause symptoms to appear faster.
> The curves show typical decrement in lung vital capacity when breathing oxygen. Lambertsen concluded in 1987 that 0.5 bar (50 kPa) could be tolerated indefinitely.
This means you could breath 80/20 nitrox at 2.5 bar, or 37 psi, or 25 meters depth, "indefinitely" in the sense of hours or days.
PS: Chronic use of 100% oxygen at atmospheric pressure causes other types of toxicity. Some of the oxidative damage therein, accumulated over the years at a normal 20%, probably directly analogizes parts of the human aging process. Other types of oxidative damage probably work faster than proportional exposure. We only start to notice damage like this in people with impaired lung function who rely on an artificial supply of oxygen boosted to beyond an 80/20 ratio, to breath.
To add to this, when diving with compressed air most people get woozy and otherwise intoxicated from oxygen around 30 meters from the surface. For some people 25 meters is enough for such symptoms to occur.
Diving on normal air, oxygen toxicity occurs around 60m.
Are you sure you aren't talking about Nitrogen narcosis ('raptures of the deep')?
Yes, he is. Oxygen toxicity causes seizures, not narcosis, and kicks in at around 1.6 bar of partial pressure (just below 65 m when breathing 21% oxygen as in regular air). PADI uses 1.4 bar to add an extra safety margin.
Oxygen toxicity is really the one thing in recreational diving that will kill you if you do it wrong, though for recreational divers the risk only exists when using enriched air(*).
Fortunately it's trivial to avoid it by only using enriched air where the sea floor is at a safe depth, but you should know the math nevertheless. For example if the sea floor is at 35 m (4.5 bar) you won't enrich air above 1.4/4.5=31% oxygen, probably more like 28%.
Oxygen toxicity is also the (or the main) reason why enriched air must never be stored in white or yellow bottles. If you see yellow you can assume it's 21%, while for any other color you must use an oxymeter before using it. Not doing so can be literally the difference between life and death.
Scuba diving is safe but a lot of the safety is about procedures, as you can see.
(*) Enriching air above 21% oxygen is done to avoid the other issue with nitrogen, which is decompression sickness. It lets you stay longer on the bottom. In other words, enriched air improves the trade-off between bottom time (limited by nitrogen) and maximum depth (limited by oxygen toxicity).
Got the symptoms wrong, but oxygen toxicity is also present from 25 meters down.
Not with 21% oxygen. 25 meters is 3.5*0.21=0.73 bar of O2 partial pressure, which is within even the strictest limits that apply to rebreathers (1.3 bar).
If you're breathing 100% oxygen for decompression, that's a completely different story and not something a recreational divers will do.
Have you got a reference for that?
E.g. https://dan.org/health-medicine/health-resources/diseases-co....
I don't see any thing that supports "when diving with compressed air most people get woozy and otherwise intoxicated from oxygen around 30 meters from the surface".
It does say:
"Be aware that oxygen toxicity is unpredictable. Divers have experienced convulsions at shallow depths under conditions where most experts would not have expected them to occur."
But that doesn't say what depth, what oxygen % and how often it happens.
It also says that oxygen toxicity is a possibility only above 21% oxygen. In fact, with regular air there are way too many things that have already gone wrong if you are at 65 m depth (or even 50 m).
It's clear from reading the document that convulsions at "shallow depths" refers to the case of breathing 100% oxygen, where 1.5 m difference is the difference between <1.6 bar (safe) and >1.7 bar (absolutely not safe).
> all the way down to 700 meters.
700m! That's wild, I mean nuclear submarine crush depths are at like 400-500m? I get that it's not like you can compare a hard steel tube with a human body but regardless, it's wild.
The published data for military submarines is the nominal test depth, not the actual design limit. The operational depth may be much deeper but that will be classified.
Recent US submarines all have test depths described by as being in excess of the same few hundred meters. In all likelihood that is a throwaway value. It seems unlikely that they produced generations of submarines that were less capable than their older ones.
> The published data for military submarines is the nominal test depth, not the actual design limit. The operational depth may be much deeper but that will be classified.
We know the actual collapse depth for an older sub: 730m for the USS Thresher (test depth: 400m), in 1963.
Test depths of current generation subs are ~20% higher; pushing them to 700m or so might be plausible, but not much more. Radical hidden capabilities would either require substantial advances in material science or drastically different hull thickness, neither of which is really feasible to hide from adversaries anyway, especially considering how little utility you get from hiding this (compared to e.g. exact capabilities of anti-air interceptors or radar characteristics for bombers/fighters).
https://en.wikipedia.org/wiki/Russian_submarine_Losharik says test depht of 2,000–2,500 meters (6,600–8,200 ft), allegedly happened in 2012 somewhere in the Arctic Ocean.
There are of course vessels that have gone deeper and are specially designed for it, but it struck me that the depth specified was close to that of 'standard' subs that are not specially designed for very deep operations
>It seems unlikely that they produced generations of submarines that were less capable than their older ones.
i wouldn't be sure. There seems to be no military advantage to deeper so why spend the money. A sub needs to hide, but it can't do any other job when too deep. sinking ships can only be done when near the surface. If the sub can get under a couple thermo layers that is good enough, any deeper is more a party trick than useful.
i'm not in the navy but that is how I read the unclassified information I have access to.
> sinking ships can only be done when near the surface.
Isn't this itself a huge assumption?
Sinking ships via upward facing torpedoes would be a huge tactical advantage at first glance. Less time to detection and deploy countermeasures or evasive maneuvers.
Perhaps, I am wrong in assuming they cannot be fired below a certain depth?
just watched: https://www.youtube.com/watch?v=V-mzZXwCn68&t=2s
while these torpedoes are going in the other direction seems like the technology for surviving, functioning and navigating depths definitely exist.
Found the SCUBA diver
Indeed, the grandparent post is a pretty good summary of the takeaways you get from taking PADI’s enriched air nitrox course (which is a requirement if you ever want to dive with enriched air).
In the olden days this was tracked manually (the ratio of your depth to percentage of air and time under water) via so called “dive tables”. The purpose and output of the dive table is to determine the safe amount of time you could dive at a certain depth without risking narcosis.
As this is a sliding window based on multiple variables - and you are very rarely maintaining a constant depth as you dive - it’s of course annoying and less accurate to hand calculate this. Modern dive computers just seamlessly calculate it all for you nowadays.
Fun fact: those dive tables were created by the US Navy conducting experiments on its own divers, there was a real human cost to acquire that information.
Numerous other training agencies also teach how to use nitrox safely. PADI training isn't specifically required (or even particularly good).
I don't see where the person you replied to claimed there was anything special about PADI.
Never done it, never gonna.
Thank _Neoshade_'s legendary story in a Reddit comment for that - https://www.reddit.com/r/todayilearned/comments/dv99nf/til_t...
With a side helping of Neal Stephenson's Cryptonomicon, and the submarine / treasure hunting arc which describes decompression sickness.
Scuba diving is great. You don't have to do deep or risky dives to enjoy it. There's a ton of fun in diving around reefs 10m down.
That story is pretty wild. And relatable.
I got myself into a little trouble when I dove the Blue Hole 16 years ago. We were warned pretty heavily how many people have died doing it, so I went in with a healthy level of anxiety. It was my second dive where the dive plan was to go to 40m, which is the limit on regular air.
The descent was surreal. You have the wall of the crater on your side, but everything else is different shades of blue. Past about 10m, there's not really any wildlife to look at, just blue. We descended straight down, going in slow motion. As we went down the blues got gradually darker and deeper.
At probably the high 20s, I started to notice I could really see the surface clearly anymore, and I started to panic. My breath started racing and I started being annoyed by my regulator in my mouth, which is an unnatural feeling to being with. For maybe a minute, I debated whether I should try to get myself under control, or signal my dive instructor I wanted to ascend. Meanwhile, we were still drifting downward. I worried whether nitrogen narcosis might affect my judgment or ability to control my panic.
In the end, I decided not to be a hero. I gave my instructor the thumbs up to ascend, and we went through the orderly process of safety stops. When we got to the top I told her I explained I was feeling panicky (you can't really communicate anything nuanced below the surface), and then I spent the rest of my tank diving the first 10m, which was relaxing, and let me finish the day on a high note.
I have over 5000 logged dives and have only suffered DCS once, with the right training SCUBA can be very safe.
that comment is a classic and certainly entertaining, but there are multiple levels of safety to prevent something like this from happening, the first of which is the wall of tombstones that greets you when you arrive at that specific dive site. To end up in that situation means to have already made a number of big, big errors.
I remember the Blue Hole as one the best dives I made, and not even the scariest: that prize goes to the time I was in calm waters at 20 meters, and the pressure regulator just failed, leaving me without air from both mouthpieces. And that's why you have a buddy...
I don't think I've ever had anything fail on me diving, but I've been with people who have run out of air (my buddy was constantly using all his up), so having to breathe off someone else's tank isn't uncommon.
As I mentioned in my sibling comment, I did have a scary time on the Blue Hole. I think my other most nervous dives were:
- Pacific dive in Costa Rica in rough seas and surge. We suddenly had visibility drop to near zero when we hit the outflow current of a river. Definitely a lesson in how quick conditions can change.
- Cavern diving in a cenote in Mexico. Nothing weird happened, but we went kinda far in, and I get nervous in overhead environments.
Running out of gas or having to breathe off of someone else's tank is uncommon. Gas planning and monitoring is a fundamental skill that every diver needs to master just to get a basic open water certification. If your buddies aren't able to do this reliably then they need remedial training.
It's good to practice gas sharing as a contingency in case of equipment failure but actually running out is not acceptable.
Yeah this is no laughing matter, i would refuse to dive with someone who lacks the basic skills to monitor their air responsibly.
same, blue hole is notorious because inexperienced divers get pressured into deep dives they haven't trained for by local guides looking to make a quick buck.
my scariest dive was when a 14 year old got separated from the group and thought it would be a good idea to continue his dive for 30 minutes.
It’s really several factors. Supplemental oxygen is common for people with diminished lung capacity, carbon monoxide exposure etc. However long term it’s not a good idea for healthy people. https://en.wikipedia.org/wiki/Oxygen_therapy
At low pressure pure oxygen can similarly be beneficial, mountain climbers eventually need supplemental oxygen for Mount Everest though a few have made the trip without it they can’t stay at that altitude indefinitely. It can even help on airplane flights as commercial airlines don’t set things to sea level.
Where healthy people run into issues is when partial pressures get well over 100% at sea level. Part of the issue is people adjust their breathing based on carbon dioxide not oxygen levels. So at say 10 atmospheres at normal atmospheric mixtures your breathing the equivalent of 210%, but you don’t slow down enough to compensate. Thus why divers care so much about gas mixtures, however people with diminished lung capacity are going to encounter issues at different levels than normal divers.
Yes, partial pressure is what matters. Normal air at 1 bar (1 atmosphere) contains about 0.2 bar of O2. Pure oxygen at sea level is 1 bar of O2.
The article you linked has a graph showing that 0.5 bar of O2 can be tolerated pretty much indefinitely, and it takes hours for significant toxicity to show up at 1 bar. Higher partial pressures cause much faster symptoms.
It is, kinda sorta, but at 1 atm you need to be breathing pure o2 for ~24 hrs before its meaningful (and longer than that before treatment is anything beyond "stop breathing pure o2". The dose isn't even cumulative. Just being on room air for 20-30 minutes resets the clock.
It's dangerous in an enclosed environment, see Apollo 1 for more details.
Yes. It’s under pressure that oxygen toxicity becomes an issue. It’s why you’ve gotta pay attention to your depth when diving with enriched air.
holding your breath for 11 minutes is asking to see the gates damn
Holding your breath for more than 11 minutes?! That's absolutely crazy, wow.
How is it even possible to hold breath for 11 minutes? I tried it last week (to avoid inhaling insecticide fumes) and could manage about a minute after trying very hard.
Being underwater does make it significantly easier, though the effect is fairly moderate in most humans: https://en.wikipedia.org/wiki/Diving_reflex
Training and genetics.
Genetics/randomness must play a significant role. When I was a teenager I could hold my breath for ~1.5 minutes without even trying. With a bit of technique I got it up to 2 minutes with relative ease, I think my max was around 2.5 minutes. The odd thing is that I had no reason to be able to do that, I was pretty out of shape, I didn't play any instruments, or have any other hobbies that would help build that kind of stamina.
On the flip side, out of all the genetic benefits one can get, this might be the lamest one. :(
I'm rather unfit these days - but as a teen I could easily do 3mins at my desk in a class. I can't remember the volume but we did a lung capacity test at school and I had the highest in the class, despite not being sporty or active at all, so I think I have genetics on my side.
I recently tried the 'Wim Hof' method, and was well over 4mins after just a few days practice, and I just went snorkelling and was able to outlast all those I went with. If I was healthier I am sure I could get longer still.
I would think that high altitude cultures with genes for handling altitude sickness would do well in breath holding contents.
Like why isn't some Peruvian on Nepalese person the record holder? Lakes too cold for recreational swimming maybe?