How Much PSI Do You Breathe Per Minute? SAC RATE Explained
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- čas přidán 5. 03. 2017
- How Much PSI Do You Breathe Per Minute? SAC RATE Explained
Figuring up your Surface Air Consumption Rate is easy as long as you have 3 variable. Air Consumed, Time At Depth, and Depth In Atmospheric Pressure.
SAC RATE= G (Gas Consumed) / T (Time At Depth) / D ata (Depth In Atmospheric Pressure)
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Thank you so much! I was getting confused with different people's explanations, but you made it VERY easy and understandable.
You are very welcome Aaron Frisch, glad you found our video helpful.
EXCELLENT TEACHER
Thanks Robert Mize for the kind words.
Great explanation. I recently took the SSI Deep Diver certification (recreational), and this was very helpful and a reinforcement of what I learned.
Hello Peakbagger, glad you liked the video, and found it helpful.
Ok thanks most appreciating
VERY informative! Thank you!
Your Welcome. Stay tuned, we are currently uploading a new series of videos related to air consumption and how to determine what tank a diver will need for any given dive, and how long it will last at any depth.
Will do.
I am taking a PADI Self-Reliant Diver course in Florida and the instructor had us all so confused. He is a 40 plus years diver the same as I am. Your explanation was so simple and easy to understand. Great job Brian
Hello John Raymond, glad to hear our video helped you out.
Bad instructors make everything complicated, good instructora make complicated things look simple.
That's what it's all about.
a bit easyer than I was shown. taking the NAUI master diver and proceding to instructor. cheers&aloha
Best of luck on advancing up the ranks. Glad our video was easy to understand.
Great videos! I actually had this question posed to me (from a curious perspective from someone the other day) because I 'surface air' dive on my gold dredge-sluice (salt and fresh water), and my rig's engine powers not only the 8-inch dredge pump, but the low-pressure air pump that compresses my 30-gallon reservoir tank...and I was asked, 'if your engine goes out, what kind of time do you get on that reservoir tank, if compression stops'...(my hookah out port feeds my 2nd stage directly)? My reply was 'between 2-5 minutes' (because once the suction-vacuum stops, I know my platform engine has shut down), which gives me time to hit 15-feet and do a 2-3 minute safety (my dives are normally 20-30 ft for 100-110 minutes each). When asked about the variance, I tried to explain that my SAC times shift, due to how much 'labor' I was exerting when 'pump goes off'...so, in a nutshell, it's all about your 'cardiovascular rate', to be truthful...that, and general fitness, that stabilizes that SAC number...
Very interesting. There are many things that can effect a diver's SAC rate. Size of cylinder, work load, etc. Your last statement about you cardio rate effecting your SAC rate is spot on. If your heart rate increases, then so does you respiratory rate, thus increasing your SAC rate.
Hi, I watched a lot of your videos and all the information was so amazing and helpful. But I found that you never mentioned about the closed circuit rebreather. So can you make a pro/cons video to compare open circuit vs closed circuit scuba. Thanks very much for your sharing.
We will be happy to make a video on the differences between an Open Circuit and Closed Circuit Scuba Systems, stay tuned. And Thanks for the video idea.
We ocean shore dive with very little shade available to set up our gear. Naturally the cylinder's PSI starts high but as soon as we enter the cold ocean water the PSI drops a good 200 to 300 PSI. I presume we should take our first PSI reading after we enter the ocean and the PSI drops. Then read the post dive PSI before we leave the water and the PSI starts to rise again? As always, great videos
Hello John Williams, this is a great example of how Charle's Law works.
This is where metric makes way more sense. Atmospheric pressure at sea level is 1 atmosphere or 1 bar. Every 10 meters of depth you increase by 1 atmosphere.
0m = 1 bar
10m = 2 bar
20m = bar
Also, psi/min isn’t a really a volume is it? It’s a pressure per minute. Litres per minute makes way more sense.
10 litre cylinder with 230 bar in it has 2300 litres - it’s all very sensible
Hello @jamescoogan8963, we train all of our students in both the Metric and the Imperial systems. This way they can choose which one they prefer. We have never really had a student come to us to say they prefer one over the other. I agree with you that the metric system is easier mathematically, unfortunately, it does have some caveats when calculating freshwater and saltwater. By training our students in both systems, we believe it makes them more educated, especially if they continue down the professional path in scuba. They will be better prepared to train their future students in both systems.
great video......... question for you; what would you think of a re-breather with no solenoid and no po2 or ppo gages ?
a 21st. century NEW DESIGN that will be called at this time.......*The Perfect Breath.
Hello Larry Rosa, I'm not sure there is such a thing that we could call the perfect breath.
When you are calculating your PSI consumed during your time at depth do you round up? My SPG has 200PSI increments, so in my experience I have with gauges (aviation maintenance) that’s pretty inaccurate. I do my OW dives later this month, so I don’t have real experience yet at any real depth. Thanks for all the videos in this series. I live the science and planning side of it.
Hello Caleb Mcelhaney, most gauges that are of high quality are very accurate. These same gauges we use when mixing gas, which we verify with analyzers prior to a dive. For divers that do not feel comfortable using analog gauges, a digital gauge is a great option, as it reads down to the exact pressure a diver has at the beginning of a dive, during the dive, and at the end of the dive.
LakeHickoryScuba I’m good with the analog gauges, I’m just used to gauges that had a lot more decisions like 25psi markings on a 5000PSI gauge.
a more accurate way- Get to 33' and maintain that depth, start swimming around, note p.s.i. and time, swim for 10 minutes then note p.s.i., then do the math. This takes the decent and ascent out of the equation. Also keep the workload the same for the entire procedure.
That will work as well. Thanks for sharing Kirk Wutzke.
Crap. I hate math. How much is your tech 40 class...and how long is the class. ( LOVE your videos!!!)
Most Tech Courses start around the $500 range. The key to the Science of Diving (the math), is finding a way to remember the formulas and what each formula is for. Once you do that, the math becomes very easy.
no sensors, no fail prone solenoid, no gages for the amount of gas in the loop, just gas material gages for materials in the tank/s.
I would suggest to take a Rebreather course before you continue. Dive safe.
my last dive gave me 17.3 PSI/min according to my MK2I. I am always curious what is the ideal rate.
Hello icareneeds, great question. Unfortunately, there is no ideal, as no two humans are identical. Physiological differences, not to mention other variables, will dictate one's SAC Rate. Thus, trying to compare one diver's to another's is not necessary. My SAC Rate changes daily based on the type of diving I am doing. A great example of this is, when I am fun diving, I have had as low as 7psi/minute to around 10psi/minute. When I am working, it has been very high around 66psi/minute. There is nothing wrong with wanting to always have a better SAC Rate, and we should strive to have the lowest possible for ourselves, but we should never try to compare and compete with others as they will never be the same.
Hi, I really enjoy your videos. I'm a fairly new diver and i'm not great at math. I recently did a few dives at Catalina Island, California. I used one of those dives to try and figure out my SAC rate. Can you tell me if I did my calculations right? Starting pressure 3122, ending pressure 714. Time under water 43 min. Average depth 46 ft. So 2408 / 43 / 1.39 =40.28 SAC rate? Seems high?
Almost. The 1.39 should be 2.39. We still have the constant atmosphere here at the surface that we have to add in. So your conversion for 46 feet would be -------(46/33)+1=2.39ata. Then you can finish the equation out. Air Used / Depth in ata / Time @ Depth. (2408psi / 2.39 ata) / 43 mins = 23.43 psi/min.
@@LakeHickoryScuba thank you very much!
You’re welcome
what formula should I use if I am using BAR value instead of PSI?
Hello Kevin Casto, the formula would be the same for the metric, just replace psi with BAR. Also, instead of using feet, you would use a meters calculation.
so wouldnt the depth in ata always be 2 ata? bc anything divided by itself will always be 1 and then plus 1 so whats the diffrence with non saltwater?
Hello charles harry. When we calculate atmospheric pressure, we first must understand what the constant atmosphere is, which is our surface atmosphere. The pressure here at the surface is approximately 14.7psi (15psi by land dwellers). This would allow us to conclude that each time we add another 14.7psi of ambient pressure to us, then we are going through another atmosphere of pressure. There are three ways to look at this from a median standpoint. If we are diving in Freshwater, then the variable we use would be 34 feet, and if we are diving in Saltwater, then the variable we use would be 33 feet. For the metric crowd, we simple use 10 meters. The reason we use different variables is due to the the density change between Freshwater and Saltwater. To calculate the total pressure surrounding us, we simply take the given depth and divide it by the variable you choose (based off the water you are diving in), and then add the surface pressure back to it (the constant atmosphere pressure here at the surface 1 ata). Hopefully this will answer your question.
Salt water vs fresh water does not make that much of a difference until your fresh water dive is at high altitudes and even in that case the important fact is the atmospheric pressure cause the water pressure is going to be more or less the same.
you will know that. does the mares quad air give you your sac rate ? Is it clearly displayed somewhere on the unit ?
Great question @TS-hz4lx. It does as long as you are using the air integrated feature (ie an transmitter). However, you will need to download it to either the Mares App or the SSI App. It will then calculate the SAC rate for you.
yes i do own the mares quad air didn't use it yet just wainting for the temperature to rise up. You have always great video. thank you for your answer
@@LakeHickoryScubado we need to buy the blue link pro to make it work work ?
@@TS-hz4lx You will either need to use the Blue Link or you can manually enter in the information on each dive, including cylinder volume and starting and ending pressures.
@@LakeHickoryScuba thank you again for your answer!
Not to be picky, but 500 psi is a bit low for this example. Like your videos...
We would agree, we simply just chose a random amount for an example. We simply wanted to show the calculation process, with out going into to much detail, as to not confuse anyone. Thanks for the likes.
& no o2 sensors ?
strictly perfect breathing volume/s...... each breath is perfect everytime...... built to deliver the exact volume of o2 / dl. or what ever gas material that is used on each scuba adventure.
some what different by being gaged by volume and not pressure...... ( this is the 21st. century ) gaged by the exact same volume of delivery valve.
I would suggest to take a Rebreather course before you continue. Dive safe.
Why doesn't the math work in reverse? Using 2200 psi at 53 feet of salt water for 40 mins equals 2200÷40÷2.6=21.15 psi per min, yet 21.15×40=846 total psi used?
You left out a variable.
It should be 21.15x40x2.6... which is 2200.
Fotgot the pressure at depht
Air can we use this surface Air consumption formula for rebreathers like we are using Nitrox mixture 60/40 for the depth at 20 meters and time spend 40 minutes..
How MUCH pounds? It's how MANY pounds!
Thank You for the correction