L13
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RMV as defined by the medical community is exactly the same, not just similar. No need to define an identical diving only term, we already have a confusing proliferation of terms.
Question Definitions for SAC and RMV?
- Thread starter scubadada
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I'm searching Google Books to try to figure out the history of this.
The first usage of the phrase "surface air consumption" dates back to the early 1900s and was a measurement of the required flow for pneumatic drills in the mining industry. It appeared in publications in Great Britain and Australia and was given in cubic feet per minute.
The first usage in a scuba context (in the Google Books database) was from 1970 in the Proceedings Volume 45 of the Institution of Civil Engineers (Great Britain). The snippet they show is:
stay submerged for 2h and complete two surveys of the triangle in 30-40 ft of water using a 120 cu. ft twin bottle breathing set . This, assuming an average depth of 33 ft , is equivalent to a surface air consumption of 0.4 cu ...
The first time the term shows up in the US is in the 1975 NOAA Manual where it only appears once in the formula under "Estimate duration of an air supply" and is given in cubic feet per minute.
I suspect the beginning of the usage of SAC in PSI per minute was the publication of the widely adopted Jeppeson's Sport Diver Manual which was first published in 1976. They did not use the exact term SAC or "surface air consumption" but they got very close to it in what is actually a very clear, useful and complete explanation.
The first usage of the phrase "surface air consumption" dates back to the early 1900s and was a measurement of the required flow for pneumatic drills in the mining industry. It appeared in publications in Great Britain and Australia and was given in cubic feet per minute.
The first usage in a scuba context (in the Google Books database) was from 1970 in the Proceedings Volume 45 of the Institution of Civil Engineers (Great Britain). The snippet they show is:
stay submerged for 2h and complete two surveys of the triangle in 30-40 ft of water using a 120 cu. ft twin bottle breathing set . This, assuming an average depth of 33 ft , is equivalent to a surface air consumption of 0.4 cu ...
The first time the term shows up in the US is in the 1975 NOAA Manual where it only appears once in the formula under "Estimate duration of an air supply" and is given in cubic feet per minute.
I suspect the beginning of the usage of SAC in PSI per minute was the publication of the widely adopted Jeppeson's Sport Diver Manual which was first published in 1976. They did not use the exact term SAC or "surface air consumption" but they got very close to it in what is actually a very clear, useful and complete explanation.
Are you guys misunderstanding my statement? I was responding to someone who thought a display of psi/min might be more helpful ay depth rather than converting it to SAC. My point was that if all I see is my at-depth rate, it doesn't help me, because I'd have to convert my usual SAC to a rate at depth to know if I was overdoing it or not. Showing me my "instantaneous" SAC while I'm at depth is exactly what I want to know.
”Different strokes for different folks” as they say - I like the real-time feedback.
I don’t need it to see that I’m breathing really hard as that is obvious as you and others have shared. However, it helps me to be more aware of my breathing and to catch the more subtle things that may drive consumption higher than it needs to be - i.e., helps to ensure I’m as Zen as possible.
I prefer the definitions I used in this document, which were based on definitions that I had found previously. SAC is for pressure "consumption", RMV for volume. They both have a role to play in gas planning. This isn't rocket science.
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A very active1st day for this thread with a lot of interesting discussion
30 votes for definitions of SAC, 50% more than for RMV. I assume more respondents are familiar with the term SAC than RMV. Sixty percent voted that SAC was volume/min/atm, only 40% that it is pressure/time/atm.
20 votes for the definitions of RMV with 95% saying that it is volume/min/atm
This topic has been discussed many times with no consensus reached, this thread is no different. When communicating your gas consumption, give your units, cu ft/liters or psi/bar per minute per atm. Volume/min/atm is cylinder independent and valuable for gas planning, regardless of what you call it.
30 votes for definitions of SAC, 50% more than for RMV. I assume more respondents are familiar with the term SAC than RMV. Sixty percent voted that SAC was volume/min/atm, only 40% that it is pressure/time/atm.
20 votes for the definitions of RMV with 95% saying that it is volume/min/atm
This topic has been discussed many times with no consensus reached, this thread is no different. When communicating your gas consumption, give your units, cu ft/liters or psi/bar per minute per atm. Volume/min/atm is cylinder independent and valuable for gas planning, regardless of what you call it.
I'm curious as to what value do people think that having both SAC and RMV refer to volume unit per time unit? I don't want to copy and paste the exercises I have my open water students do for determining their gas consumption rate (RMV), swim rate, and apply that to a dive plan where they check their cylinder pressure versus what they calculated it would be. I do this for the sake of confidence building that they know how much dive time they have.
Don't (follow my example) and let it keep you from getting enough sleep.I'm shocked by how many people are wrong.
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