Average Gas Consumption

[scubadada]

Apparently, I have both above and below average consumption. At the end of a week in Cozumel this summer, with no wet suit, I was down to around 10 L/min. This weekend in Catalina, 8/7mm suit, hood, 3mm gloves, surge, current, etc., I was a bit over 20 L/min. In customary units, .35 to .75 ft.^3/min. So I encourage everyone to take the data here with a huge grain of salt.

Hi @wnissen

Or, your average gas consumption balances out the different environments you dive in and the different equipment you use. You use the average to predict about what your gas consumption will be.

If you know you are diving in Cozumel, plan accordingly knowing your previous performance. If you will be in Catalina, do the same thing.

I have my RMV for almost all my dives since 2010, 1792 dives. The avg is 0.36 cu ft/min with a std dev of 0.04 cu ft/min. If I'm diving with my wife in Bonaire, I know my RMV will mostly be around 0.3 cu ft/min. If I'm doing one of my solo drift dives in SE FL with brisk current, cold water, poor vis and am carrying my flag and camera, I know my RMV will be in the low 0.4s cu ft/min. Plan accordingly.

So, for your two trips, your average RMV is right about avg, around 0.55 cu ft/min. You go back to Cozumel it will be on the lower end, back to Catalina, closer to the high end. You appear to have a lot more variation than I do, but you also appear to have less dives. It might also be helpful to keep track of range so that you know the extremes, My range is from 0.24-0.63 cu ft/min. The lowest was mostly kneeling or standing in the sand watching Great Hammerheads in Bimini. The highest was the opposite, a cold, dark, high current dive on the stern section of the Chester Poling in a wetsuit in Cape Ann, MA.

I did not start recording my RMV until I had about 450 dives, my RMV was already pretty well set where it is today, just a little lower with less variation. I would imagine another experienced dive, like @tursiops, has results that look somewhat like mine, and are used similarly.

Best of luck with your future diving.

 

[wnissen]

Hi @wnissen

Or, your average gas consumption balances out the different environments you dive in and the different equipment you use. You use the average to predict about what your gas consumption will be.

If you know you are diving in Cozumel, plan accordingly knowing your previous performance. If you will be in Catalina, do the same thing.

I have my RMV for almost all my dives since 2010, 1792 dives. The avg is 0.36 cu ft/min with a std dev of 0.04 cu ft/min. If I'm diving with my wife in Bonaire, I know my RMV will mostly be around 0.3 cu ft/min. If I'm doing one of my solo drift dives in SE FL with brisk current, cold water, poor vis and am carrying my flag and camera, I know my RMV will be in the low 0.4s cu ft/min. Plan accordingly.

So, for your two trips, your average RMV is right about avg, around 0.55 cu ft/min. You go back to Cozumel it will be on the lower end, back to Catalina, closer to the high end. You appear to have a lot more variation than I do, but you also appear to have less dives. It might also be helpful to keep track of range so that you know the extremes, My range is from 0.24-0.63 cu ft/min. The lowest was mostly kneeling or standing in the sand watching Great Hammerheads in Bimini. The highest was the opposite, a cold, dark, high current dive on the stern section of the Chester Poling in a wetsuit in Cape Ann, MA.

I did not start recording my RMV until I had about 450 dives, my RMV was already pretty well set where it is today, just a little lower with less variation. I would imagine another experienced dive, like @tursiops, has results that look somewhat like mine, and are used similarly.

Best of luck with your future diving.

Yes, part of the reason I posted is because I hadn't done any significant warm water diving and was surprised at the disparity. I do use it for basic planning purposes, for instance I brought my 12L / HP 100 tanks to Catalina even though it was a schlep, because I knew from experience that I wouldn't be able to guarantee a 100 cu. ft. tank of any kind on the boat.

Not being a statistician, I don't have a professional opinion on the use of this data, but I do worry that folks will imbue the numbers with more meaning than is perhaps warranted. My impression is that most people want to know how they compare to other divers, whether for bragging rights or just to know. But if conditions is half the driving factor, then you're really better off comparing against the other divers in your party. Similarly, if your body composition tends toward a higher basal metabolic rate (ahem, me), then it doesn't really make sense to compare against a small person.

If I were doing a linear regression, it wouldn't surprise me that the skill of the individual is less significant than environmental factors and body composition.

 

[scubadada]

Hi @wnissen

Clearly, knowing your gas consumption is most valuable in gas planning for your own dives. Comparison with other divers does not have much value.

Predicting gas consumption is more complex than I would have thought. Gender and body size obviously play a role, but there are other factors we know less about. I recently described my own situation in another thread Question - Definitions for SAC and RMV? I am an older (69 year old) man, overweight, in pretty good but not great shape. My gas consumption is now, and always has been, better than average. I have thought about it but have no particularly good explanation. Exertion and getting cold are the only two easily identifiable factors increasing my gas consumption. Psychological stress probably also plays a role but is harder to identify or quantitate.

It would be very interesting to have you come back in a few years to describe your gas consumption and what you have learned

 

[tursiops]

In Antarctica (temps 32-33F) I dived with a camera, a drysuit and integrated hood, pretty much all the underwear I owned, a stuffed weight harness, dry gloves and a steel 100, depths from 33 to 63 ft. My dive times were typically 30 mins, gas limited. Assuming 53 ft for 30 mins and 85 cuft used, that's about 0.92 cuft/min, which is more than twice my warm-water AL 80 3mm wetsuit diving.

 

[scubadada]

38,000 views since July 2016, 13 more votes in the poll since the last update

Median, mode, and weighted average 0.5-0.59 cu ft/min or 14.2-16.9 l/min

Thanks for participating in the thread and voting in the poll. If you have not voted in the poll, please consider doing so. If your average RMV has changed, please change your vote.

Good diving

 

[scubadada]

39,000 views now and a respectable 646 votes in the poll

Median, mode, and weighted average 0.5-0.59 cu ft/min or 14.2-16.9 l/min

If you have not voted in the poll, please consider doing so. If your average RMV has changed, please change your vote.

Best of diving to everyone

 

[Rearviewmirror]

Quite proud to have joined the middle of the bell curve after a year of working pretty hard to get my gas consumption down to a reasonable level. I think I'm naturally quite a deep breather/take big breaths and so it has been a constant practice, and also required a lot of awareness to get to recognize when I'm task loaded and breathing rate creeps up.

After restarting scuba diving in April 2022 (with a spicy SAC rate of 0.72-1.08 cuft/min - mostly in shallow 30fsw dives) I've managed to get down to 0.54-0.58 cuft/min on my most recent trip mostly in 60fsw, including my first dive over 60mins. This is definitely no mean feat for a lot of divers, but it feels like a meaningful progression in my skills.

One small tip for others struggling with SAC. I read an offhanded comment about divers being slightly negative when they think they're neutral - and so having to fin more to stay level in the water column. I've been a bit gutsier on adding air to my BC on this trip, and if I'm not actually rising in the water column, calling that good. I am not sure if that's made a big difference but on this trip I've gone from mid 0.6 cuft/min to sub 0.6 cuft/min with that one change.

 

[scubadada]

Well more than 40,000 views and 655 votes in the poll

Median, mode, and weighted average are 0.5-0.59 cu ft/min or 14.2-16.9 l/min

If you have not voted in the poll, please consider doing so. If your average RMV has changed, please change your vote.

 

[scubadada]

Another 1000 views, now over 41,000, and 661 votes in the poll

The median, mode, and weighted average remain 0.5-0.59 cu ft/min or 14.2-16.9 l/min

If you have not voted in the poll, please consider doing so. If your average RMV has changed, please change your vote.

Good diving to all

 

[scubadada]

Happy 7th Birthday

This thread in now 7 years old with nearly 42,000 views and 662 participants in the poll