Average Gas Consumption

[60plus]

I never pay much attention to SAC because I have fond it has little bearing on actual dive times. There are many factors that can affect air consumption and cause it to differ during a dive. Late last year I was asked to lead a dive group (of strangers) through a wreck at depths down to 32m. I knew my way through the wreck pretty well and on this occasion decided to do the full length right at the bottom in the lowest parts of the ship. Although I did not feel stressed just the effort of looking round and checking on those behind me resulted in a significant increase in air consumption (actually nitrox 32)

 

[scubadada]

15 more responses to the 2016 poll since the last update. If you haven't voted in the poll, consider doing so. If your average RMV has changed, you are able to change your vote. Please see post #1 for imperial/metric conversion. For the 2016 poll, the median and mode are both 0.5-0.59, as is the weighted average

 

[Divin'Papaw]

Who the the heck has an RMV consistently less than 0.3??!! Gotta be a tiny female gymnast or dancer. Wow is that sipping gas! I can occasionally get mine around 0.36 but that’s super rare for me. But under 0.3? Wow!

 

[rhwestfall]

Who the the heck has an RMV consistently less than 0.3??!! Gotta be a tiny female gymnast or dancer. Wow is that sipping gas! I can occasionally get mine around 0.36 but that’s super rare for me. But under 0.3? Wow!

At 6'-7" and 245#, it sure the heck isn't me. I am darn happy to be at 0.5 - 0.6, and hit 1.0 in the dry suit and doubles....

 

[rhwestfall]

I know of a member here who does some amazingly long dives at BHB and thereabouts... Probably her...

 

[dirkhh]

Who the the heck has an RMV consistently less than 0.3??!! Gotta be a tiny female gymnast or dancer. Wow is that sipping gas! I can occasionally get mine around 0.36 but that’s super rare for me. But under 0.3? Wow!

I personally know two divers whose average is below .3 - one of them is a ~100lbs female, the other one a >220lbs male in his 50s with around 13k dives. I have been on quite a few dives with both of them, so these are real numbers, not made up bragging... that said, I'm a 250lbs male in my 50s and in warm water my average is below .4

Note that all of these numbers are Subsurface data, so taking gas compressibility into account, which depending on your tank type will give you slightly lower (but, in fact, more accurate) numbers than what you'd get with naive calculations

 

[Divin'Papaw]

I know of a member here who does some amazingly long dives at BHB and thereabouts... Probably her...

I've done 3 hrs at BHB and there I can get down to around 0.35. A woman would probably be under 0.30. But averaging below 0.30 ... that is impressive air consumption!!

 

[scubadada]

Who the the heck has an RMV consistently less than 0.3??!! Gotta be a tiny female gymnast or dancer. Wow is that sipping gas! I can occasionally get mine around 0.36 but that’s super rare for me. But under 0.3? Wow!

I've wondered who those divers are too. Of course, voting in the poll is on the honor system.

I've always had good gas consumption, not sure why, I've often wondered if some of it is from having been a competitive swimmer from age 4-18, something to do with the breathing pattern, gas exchange? I have my RMVs for 1,547 of my last 1,564 dives, dating back to July 2010. I had 443 dives before I started using an AI computer and log application to calculate my RMV. My RMV is 0.36 +/- 0.04 (mean +/- std dev). I only have 25 dives with an RMV of <0.30 and 16 of those are in the 0.29s. All of these dives were in very benign conditions, either lazy drifts or essentially no current,16 in Florida, 6 in Bonaire, 2 in Grand Cayman, and 1 in Roatan.

I generally use a RMV of 0.44 for my gas planning, that should cover more than 97% of my dives. I have learned that being cold has as much influence on my RMV as exertion does. My RMV has not changed significantly in the more than decade I've been checking it. The average is just a touch lower and the variation, a little less. I'm 67 years old, 5' 10", 185 lbs. Not svelte, but in pretty good shape for an old guy.

 

[scubadada]

Hey @dirkhh

Your graph was a great idea. I have known that my RMV was adversely affected by colder water for a long time, but I have never taken the time to prove it. My graph is not as pretty as yours, did it with Excel. The scattergram represents my last 533 dives from the beginning of 2018 until the present. The line is the linear trend. Clearly, as the temperature goes down, my RMV goes up. My RMV for these dives was 0.35 +/- 0.03 (mean +/- std dev). This needs to be taken with a grain of salt as many of my colder dives were also more strenuous. Revillagigedos and Galapagos were more challenging dives than those in Bonaire or Grand Cayman. Florida represents nearly the entire temperature range.

 

[boulderjohn]

I've done 3 hrs at BHB and there I can get down to around 0.35. A woman would probably be under 0.30. But averaging below 0.30 ... that is impressive air consumption!!

I've wondered who those divers are too. Of course, voting in the poll is on the honor system.

I know someone who makes such a claim, and I believe him. I have dived with him, and his air consumption is extraordinary. (Well, it was. He is pretty much a rebreather diver now.)

I hesitate to say here how he does it, because people will scream, but I will reveal it. He skip breathes. Seriously. He would practice it on the surface, sometimes on long car trips.

Notice I am not advocating it; I am just a reporter.