Why is PO2 important for divers? | SCUBA 101
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- čas přidán 28. 04. 2023
- Jonathan explains the concept of PO2 (Oxygen partial Pressure) and how it relates to Maximum Operating Depth (MOD) of a breathing gas, and how rebreathers gain advantage by changing the percentage of oxygen in the breathing loop at different depths to maintain a more ideal PO2 and minimize the amount of nitrogen in the breathing mix. It's not as tricky as it sounds!
WARNING! JONATHAN IS NOT AN INSTRUCTOR AND THIS VIDEO IS FOR ENTERTAINMENT PURPOSES ONLY. ALWAYS SEEK PROFESSIONAL INSTRUCTION FOR SCUBA DIVING.
Other videos that are relevant to this one:
WHAT IS NITROX?
• What is Nitrox? | SCUB...
WHAT IS A REBREATHER
• What is a Rebreather? ...
ADVANTAGES OF REBREATHERS
• What are the Benefits ...
TYPES OF REBREATHERS
• What are the Different...
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I don't dive but between you, Dive Talk & Edd's videos, I've learned so much. I've learned about safety, open air and rebreather diving. ❤
Been diving a long time. Have nitrox ,SCR,advanced OW , etc. This by far is the best explanation for P02 that I've heard 👍🏼
Thanks!
@@BlueWorldplus I’m broke as heck what job should I get to be able to try this 😂😂😂 man I want to do this so bad
@@davidgilbert2998 hard question
Bcause everything is so expensive with scuba
Yet metric system would have been convenient 😏 jk !
Jonathan you have explained PO2 better than anyone here on CZcams I like watching you vids keep em coming from Australia.
Jonathan, this is an excellent presentation/explanation of partial pressures! As a technical instructor/rebreather cave diver, I just wanted to mention that for O/C, we teach P02 limits up to 1.4, not 1.6. We do deco (only technical) at 1.6, but for recreational Nitrox users, I believe that most agencies still set their standards at 1.4. For rebreather, as you said, around 1.3. I just mention the 1.4 so novices don't think they should dive Nitrox to 1.6. And BTW, metric is much easier :)
I thought I covered that with the setpoint at 1.3 and the absolute safe maximum at 1.6 but I guess it wasn't clear enough if it didn't come through. It's really hard to do a "lecture" on camera and be totally satisfied with it afterwards! But as I mentioned...these videos are informational only...they are not meant to replace training. I'm just trying to help people understand the basics...this is not a substitute for proper training by a professional!!
@@BlueWorldplus Absolutely, these are some of the best lectures on this subject. You did a great job explaining the principles and pragmatic realities. And yes, you talked about setpoints for rebreathers. But we just want to be clear for safety purposes, so some novice Nitrox diver doesn't say, "Well, Jonathan says 1.6..." And BTW, you should be very proud of what you are doing. You have a gift for breaking everything down to the fundamental. That's good teaching.
I’ve looked around for a good video for partial pressure and this is hands down the absolute best.
Wow, thank you!
As a newly qualified BSAC OWI that was a brilliantly simple explanation of PO2 👏👍
Thanks!
Finally someone explained the math behind dive. Great didatics.... thanks master.
Very well explained and easy to follow. So much easier than trying to follow it in instruction manuals.
Thank you so much for this video. I have watched several videos trying to understand p02. You made it very clear! I have a much better understanding now!!!!! Awesome!
Probably one of the best videos I’ve ever seen on this topic. Well done.
So much easier in meter's then again from Australia thanks Johnathan.
Jonathan, thank you for all your videos. I am OWD certified and working on my AOWD and Nitrox curses. I am binge watching your scuba 101 and all your rebreather videos and understanding SO many things. Amazing explanations on apparently complicated topics. Thank you so very much!!
I’ve been diving for 45 years. This video is the best PO2/Nitrox mix explanation I’ve ever seen or heard! Great job, and is easy to understand!
Jonathan, you are brilliant explaining everything. Thank you and keep up the great video creating.
Cheers Mr, it's always much easier in metric. Keep up the good work.
This is a great refresher course for me!!
The magic circle makes it easy to understand and a quick way to figure it out. Great video.
My complaint with the magic circle technique is that it's basically a shortcut for "plug and chug" the numbers without necessarily understanding the concept. If you like the magic circle as a way of remembering the math, that's fine. But I would hope that by the time someone has watched and understood my video, they actually don't need the magic circle because they fundamentally understand the concept and the math.
@@BlueWorldplus I totally understand and concur. Thanks for the reply. I love your work, and I love scuba diving.
This is an excellent explanation for a newbie to further understand the world of PO2 / Nitrox values and diving depths. Thank you Jonathan!
Thanks!
Thanks 🙏 this is the best video I ever watched about this topic!
Thought I already had a solid understanding of PO2. Now I know I do...thank you!
I love your videos! I don't even dive, but an fascinated by the subject and methods. You are just amazing at explaining this stuff!!! Was having to worst time understanding what Po2 is and how it's calculated. Watched your video, and it just instantly started making sense almost instantly! I'm not great with math either, but was able to understand the quiz at the end and get the right answers just fine!
Thanks again! Subscribed!
Thank you and welcome aboard!! New video tomorrow!
@@BlueWorldplus You're welcome! Awesome! Looking forward to it! Enabled the bell for your channel so I get the new upload notifications! ;)
Man you're a LEGEND! Thanks for this explainer! My question is: wouldn't a diver still get gas narcosis as they go deeper when the rebreather decreases the Oxygen percentage which would increase the Nitrogen percentage? I guess that's why Helium is added to account for it. Now the actual question is: Does Helium have any effect on humans at greater depths?
I'm going to do a trimix video soon which will talk about what happens when we add helium. But you are exactly right about narcosis. As you go deeper on a rebreather holding a constant PO2, the oxygen percentage goes down, which means the nitrogen goes up, and you end up with more possible narcosis. It's worth pointing out however, that at a set point of 1.3, you won't get down to 21% oxygen until 170 feet, which is way too deep for nitrox blends anyway. At 130 feet and a setpoint of PO2=1.3, your oxygen is about 26%, which is still quite a bit more than air (21%), so you are getting slightly less narcosis than you would on air.
Thanks for the video! Super informative and I love how you've laid it all out. Hope to have the pleasure to meet and dive with you boys one day!
Thanks!! I'm impressed how many people are taking the time to watch a math video. LOL!
excellent explanation of P02, you have the gift of teaching... keep it up
Thanks! I used to be a college professor. (Seriously!). I kind of miss it.
Great videos!!!
Very cool video! I watched another video, black and white made for the US Navy that dealt with PO2 topic.
I just understood po2 better in your short video than I did at the end of my tec 40 cert. 👍
Soo good explanation ❤❤❤❤❤
this explanation made me get it, thank you sir!
Glad it helped!
It fascinates me how gasses behave and interact with our bodies under pressure, and it also makes me think of all the people who suffered so that we could learn all of this, through trial and error. Thanks to those that have died and/or been injured, we know how to keep safe under pressure and prevent more loss of life. It’s really amazing to think about, thanks for making these videos, I really enjoy them, though I’m not a diver, I would love to get certified some day, if that day ever comes.
We have the Navy to thank for a lot of this information. They did a lot of testing back in the early days of hard hat diving.
The more I learn about DCS the more I realize how much we still don't understand. We're standing on the shoulders of giants but still have a way to go.
I recommend taking the Deco for Divers webinar course by Mark Powell, or reading his book. Learned so much from that.
@@Yggdrasil42 I’ll look into the book, sounds interesting. Thanks!
I am studying for nitrox now(i never got it when i certified years ago.) This was very helpful.
Excellent presentation!!!! I finally get it!!!!!!
That's what I like to hear. The math is simple when you understand the concept.
Amazing!
Jonathan I am watching all these SCUBA 101 videos and I am learning so much, thank you so much for all of these educational videos, you are a great teacher
Glad you like them!
good video !
Very good thanks
Very well explained ‐ nice video! The only thing to add would be the missing 2 concerning nitrogen as it is diatomic just like oxygen ;-)
Yeah I realized that later. Oh well. That's what happens when you are doing very casual off the top of your head stuff.
Another really good video! one little thing that perhaps maybe isn't that obvious is that whilst water is around 800 times denser than air (at sea level) because air is a gas and is compressable, but water is a liquid and isn't (theoretically) the height of a column of air that exerts the same pressure as say 33 feet (10m) of water is not actually 800 times taller (26,400 feet, 8,000m) but much more!
What happens is that the gas itself gets compressed so it's density changes markedly with altitude. ie the higher you go the less desnse the air gets. Water however experiences effectively no density change with depth (wihin the range of scuba anyway)
The side effect of this is fortunately to make all our diving calculations basically linear in nature, ie every 33 feet you decend the pressure goes up 1Atm, this makes things much much easier for us,compared to the exponential nature of air density with altitude! (however, you do need to consider this for your altitude compensation deco calcs (diving at altitude) or for when flying after diving at sea level.... ;-)
VERY good point!
Good explanation, just one minor point.
Water exerts 1atm of pressure, not 1 ata.
The ending "a" in ata, actually means absolute.
i apologize for my engineering orthodoxym just couldn't resist
:)
Kiss rebreathers? Hm, isn’t rebreathing the very definition of bad breath 😂
God! I crack my self up😂😂😂
Nitrogen is N2, like oxygen (O2). Great video.
Yep, I know...it was just too much work to go back and fix it!
Mr Johnathan sir.
My father and me were once UNDERWATER ROV technicians.
Youngsters nowadays,
today modern punks from America, London or Singapore.
- We are not doing trivia crazy things.
Great video! Is there somewhere where I could access the partial pressure excel file?
It's just something I whipped up to help me quickly get numbers without having to do the math. I'm afraid to release it for fear of liability to be honest. Let me ask our legal department (Cameraman Todd) what he thinks.
Way to represent!! KiSS!
LOL...Subtle, right?? Ha. 🤣
Jonathan, I had no idea you have this channel, let everyone know to subscribe here on your main channel!
I am an open water diver only. I just watched your rebreather video explaining the difference of rebreathers, followed by this video of pO2. Awesome explanation! It leaves me with a question though. You noted that an advantage of the CCR rebreather is a small bottle on your butt, a dilutant on 1 side and a bailout bottle on the other side. Although your rebreather adjusts bases on pO2 adding O2 and your diluant (assuming air or nitrox), then your bailout bottle and diluant can’t be used below 118 ft on air or less with nitrox. if your rebreather fails because the pO2 would be above 1.6. So where is the backup air at depth with rebreathers?
I just redid my reverse math of 1.6 pO2 back to depth and got 218 feet not 118 feet. So now I see that I could still use bailout air up to a max of 220 feet. And at that depth you have decompression time problems on bailout air at that depth, as well as other problems. On to watching the helium videos or trimix. Love your videos, very well explained despite my maths. 🤣
A rule of thumb is that the best diluent mix is the same as the best OC mix. But when you start going deep, things get more complicated.
Will you do a video eventually on the "O2 clock" I think I've heard it referred to as?
Yes, that's a good topic. I decided not to mention it here because...one step at a time!
Ok I assumed it was complicated but I could never find anything that explained it.
Thank you so much for the video. I've been searching for video to help me understand and have some knowledge of PO2. Just recently received my c-card. Purchased my new dive computer and was having a hard time understanding po2. Thank you so much.
Please do a Trimix video!
Coming!
Nice shirt!
REPRESENT! 😎
Love the video!!!! Hate the metric system!!!! LOL!!!
The metric system is so much more logical and easier...it's just that my brain thinks in feet, not meters!
You should have a meet and greet.
We are having one at the Tennessee Aquarium on May 26.
Finally a PO2 i can understand, sorry Gus and Woody.
is your excel file available somewhere?
Great video. So why is recreational limits on air only 130ft if our p02 is only approximately 1.0 at that depth?
Great question! Because it's based on the nitrogen narcosis of the Nitrogen. A 130 feet on air, most people are fairly heavily impacted by narcosis. Of course some people are more susceptible than others, but as a general rule, going deeper than 130 on air for most people is not a great idea. I know it's not for me!!
@@BlueWorldplus makes perfect sense. I didn't even consider that. Been diving here in the PNW. For about 20 yrs. And have been pretty deep on many occasions and have never really experienced nitrogen narcossis at least not that im aware of.
@@johnmontgomery2735 In one class I took an interesting test to illustrate narcosis. It was a 5x5 grid of numbers from 1-25 in random order. The test was to touch a number then your nose, then the next number in order. The test was given at the surface and then at about 80 feet. On the surface I did it in something like 25 seconds. We then got in the water and went to 80' and did the test. I felt fine at that depth, nothing at all out of the ordinary. I could tell that I wasn't going as fast, but the biggest time loss was spent looking for number 26!
@@tcoiler too funny
How can we get the excel sheet?
Great video!
btw, metric system are way easier to calculate 😂😂
True!
Is there any way to get a copy of your spreadsheet Please ?
At 10 meter the atmospheric pressure would be 2 atm. Isn’t it ? Please correct me if i am understanding wrong. 22:25
Hey Johnathan, I thought that oxygen was considered to be equally as narcotic as nitrogen at depth?
No, oxygen is not narcotic, it's actually toxic and will cause convulsions at a high enough PO2. This is why you need to understand it.
well ****. thank you.
So a rebreather is constantly adjusting your mix as you dive? I had no idea!
Yes. So you are always breathing the ideal gas mixture.
1:15:
Excuse me sir.
Pardon me.
Before Scuba Diver,
There was the heavy golden Underwater Juggernaut.
You are talking about mixing Nitrogen gas with Oxygen.
Hi Jonathon could I please get a copy of that excell speedsheet please:)
Is that mean the less portion of oxygen the deeper you can dive？ For example，if you have 21% oxygen，base on the PO2 limit is 1.3，the deepest you can dive is 51m. But somebody can dive for more than 250m，how can he do that？If the PO2 limit is 1.3，than the oxygen portion will be only 5%. Is that possible？
Yes, that's exactly right. In deep trimix (oxygen/nitrogen/helium) mixes, they need to make a blend that reduces the oxygen to a safe level for depth. But that creates a blend which is hypoxic at the surface---meaning the oxygen is too low to breathe it shallow. So it's a deep breathing mixture only. That's extremely technical diving.
like for metric units
Trimix please!!!!!
That's going to be a fun one. It's coming.
Fantastic and informative but like everything else, metric is just so much simpler. I find it so bizarre to talk about pressure / atmospheres without using meters and bar.
So true.
Metric its 101.325 Pa = 101,325 kPa = 1013,25 hPa = 1 atm
You metric guys always get your periods and commas backwards. 🤣
yay metric!
Definitely easier for ppO2 calculations.
Honestly, looking into sidemount and gas matching looks way simpler.
the calculations remain the same, metric sys just make it slightly easier ✌️
I know Metric is complicated: 1 atmosphere is 1 bar.
What is the pressure at 10 msw? 2 atmosphere, or 2 bar.
What is the pressure at 20 msw? 3 atmosphere, or 3 bar.
What's your PPO2 at 20 msw? 0.63 ata, or 0.63 bar.
I know I know, but here in 'merica we think in feet!
The math is so much easier if its just 10=1 atm instead of 33=1 atm
That's true!
Dude - if you're going to refer to Oxygen by it's formular 'O2'... then you should also show Nitrogen as N2 (not just N).
Sorry I'm not a chemist.
@@BlueWorldplus not good with critique either... same deal as those force fins!
But Jonathan, BlueHQ is under water, so your PO2 is in fact not .21 on air! 😜
Right!! ;-)
thanks for the non-imperials
It's good that you'll having a meet and greet. It should be brought to Wisconsin, maybe in Milwaukee.