Average Gas Consumption?

[ianr33]

Great thread, thanks to all who have added their SAC rates.

I find a good baseline average for SAC rates is .5 (really good) to 1 CFM (Average)

Keep reporting your SAC rates and we can try to do a "Scubaboard" average

Chris

You may find some guys lie about the size of their SAC.

 

[ianr33]

...

Stupid Software

 

[j2s]

To give you an idea of variables...I dive w/a woman who is a long time chain smoker; pack-pack 1/2 a day for years. Smokes to the moment she gets in the water and lites up almost as soon as she gets out....She gets at least 2 hrs from an AL80 [3000-3100PSI ] and most often has 800-1000PSI left...She does the same dive as the rest of us...I've have seen her get 2Hrs and 45mins from the same tanks on low exertion dives w/400-500PSI left :shocked2: !!!!...Highly unusual and not the standard, but it shows that there are no real hard rules w/SAC rates and many variables effect it......

 

[Q1988]

What I have found helpful is to keep your bouancy correct. That is very little air in your BC/WING. When I need a little in my wing I inflate orally. Using multi-tanks you will bet used to switching regs or get a combo reg/will inflator system.
Another thing that I have found nice is a well balanced adjustable secondary. No snapping open and shut, just an nice flow. I have a G250 that is sweet.
Another point is try hooking up with a buddy that does not have to swim all over a wreck or a site. You find lots of things to see in a small area. get a good light that is nice and keeps your excitement level under control. Nitrox may help also
Dive evertime you get a chance.

 

[TSandM]

We calculated SAC rates for our three OW students on their first two dives yesterday, and the results ran between .62 and 1.0. I think that's pretty typical (all males of fairly average proportions).

I remember a long time ago, somebody who works as a tropical DM claiming he had a sac rate in the high .2's -- nobody believed him. But mine runs in the low .3's, and I have turned dives on gas when cave diving with a 6' man. It astonished me.

 

[Zung]

One of my favorite dives is a "3rd" dive of the day, at a place called Roca Suwanee in the Sea of Cortez: it's about 10 m/33 ft deep and literally covered with fish. I'd grab the tank from my 2nd dive, go down with what's left in it, usually 50 bar/725 PSI, do half an hour, and come back with 0.

Of course you shouldn't tell anyone about it, it's not safe, bla, bla..

 

[matthewmark_john]

I'm one of those divers who does care about getting as much time out of the dive as (safely) possible. That said, when I dive with heavy breathers, the shortened dive time doesn't really bother me since I'm usually just glad to have a buddy. Gas consumption is not even on the list of what I think makes someone not such a great buddy.

I've had a lot of inexperienced divers as buddies over the years, and have yet to be the one who's low on air first. If I surface with 2000 left, that's okay, because I just consider my unused gas to be a good safety margin. I'm not sure I would be all that comfortable if I was always ending with 500, frankly. Since I do want to extend dive time, I bought a higher capacity tank. I use my own standard cylinder, and let my buddy use the bigger one. Better buoyancy characteristics of HP steel plus higher air capacity equals longer dives in my experience.

One thing to remember, though, is that higher capacity tanks, especially 120 and more, give you the ability to get in much worse deco trouble than AL80s. Of course, you should be closely monitoring your NDL time closely anyway, but it's something I'm always conscious of when I give a newer diver a larger tank.

 

[matthewmark_john]

Here's an interesting kink. From a dive log of mine (from an air integrated computer, regular air) showing the depth profile and varying sac rate, it appears that SAC (red line in pic) may be a function of depth (purplish area). Moreover, SAC rate improves as I go deeper. I've checked about my past 100 logs with this computer, and they invariably follow this pattern. And I don't think this is explained by differences in activity level at different depths, as I don't think I'm much less active deep down on the wall than at its upper levels.

Has anyone else noticed this? While of course total air burned will increase as depth increases, it will not be linear. In other words, calculating gas consumption by multiplying SAC rate by ATM may not be accurate. I would sure love it if anyone else would chime in on this with their data. I know it's a bit of a tangent, but we could always put it in its own thread if the OP isn't interested.

 

[Chris Horn]

I'm typically on par with the op. I average about 35-40 min on an AL80 in 30ish feet of water, although a bit warmer. However I got a solo dive last week and to my surprise I came up with a 53 min dive. The deepest I was at was 26' feet, most of the dive was 18'-20' range. I wasnt doing anything special, just playing after work. I really think the fact that I wasnt "chasing" around a partner this particular time was the biggest factor in my increased time as I was able to focus on me and not always swimming circles and backtracking to find "them". Extending my dive time is something that I also want to work on, but as everyone says, just dive it will come. I sure hope they are right!

 

[smorneau]

Here's an interesting kink. From a dive log of mine (from an air integrated computer, regular air) showing the depth profile and varying sac rate, it appears that SAC (red line in pic) may be a function of depth (purplish area). Moreover, SAC rate improves as I go deeper. I've checked about my past 100 logs with this computer, and they invariably follow this pattern. And I don't think this is explained by differences in activity level at different depths, as I don't think I'm much less active deep down on the wall than at its upper levels.

Has anyone else noticed this? While of course total air burned will increase as depth increases, it will not be linear. In other words, calculating gas consumption by multiplying SAC rate by ATM may not be accurate. I would sure love it if anyone else would chime in on this with their data. I know it's a bit of a tangent, but we could always put it in its own thread if the OP isn't interested.
View attachment 98531

I am very interested in the subject. On Sunday I did 2 deep dives 90'-100'. My first such dives. I got much more out of my tanks than I expected even with the cold of depth. I marked it up to just being very relaxed at depth. I calculated my SAC based on a rough average depth and it was around .7 (no air intergration). It just seemed to be better at depth without as much surge.