To answer any questions people may be having....
I am 5'8 120 pounds.
The tank was aluminum.
All the figures I posted earlier are accurate.
I am sorry if there was any confusion.
How did you determine your average depth?
Thats my only question. I have had dives of ridiculously low SAC's as well, some in the high .2x's, most are in the high .3x's and never more than .4x's... The math to figure out average depth is next to impossible for the average dive most people do... Here's an example of why: On my average guided dive with certified divers along the wall, I'll take them to about 70 feet for about 20-25 minutes, air consumption permitting, then ascend to the top of the wall, usually around 30 feet, for the remainder of the dive, we get back to the boat, hang out under the boat, 750 psi, ascend, safety stop, back on the boat... Now, casually, you may say thats easy to calculate the average depth, but lets look at the reality of it. After its all said and done, our dive computer says 60 minutes. We easily say, well, ok, we had a max depth of 70 feet, we did that for half a dive, then followed the top of the wall, 30 feet for half a dive - 70+30 = 100, divide by 2 for average, we say 50 feet. Its not that easy though. It was really 25 minutes at a max of 70 feet, that was really spent somewhere between 60 and 70 feet, then it was 32 minutes at 30 feet, which was really spent somewhere between 20 and 30 feet, then it was 3 minutes at a safety stop... Boy the math just got way harder. Weighted average, geez... (70x25 + 30x32 + 15x3) / 60 Now, our average depth is 45.9 feet. Not a huge difference, but, lets average using 65 feet as our average deep part and 25 feet as our average shallow depth. Save all the math, its a little deeper than 41 feet. Now, lets input my average true SAC (as computed by my dive computer) and say it calculated it using my 41 foot average depth. Simply changing the way I found the average depth, it could mean I artificially changed my SAC to a much lower .34.
Now, if you found average depth the correct way (by knowing exact time at all your different depths), then I digress.
One other way of artificially changing what your SAC rate appears is by having either a tank or SPG off a little. We fill all of our tanks to 3000 psi, give or take. Every once in a while, after its cool, some end up close to 3200 psi. Also, I've seen SPG's vary a few hundred psi one direction or the other and nothing really be wrong with them. Lets see how that effects our SAC calculations. For instance, take my 3200 psi tank, then couple that with a SPG that is off a few hundred, and you might start with what seems like a 2900 psi tank per your gauge, but in actuality has 300 more psi than your gauge thinks. Well, gauges are usually off through their whole spectrum, thing is, that they are off more, the higher pressure you get. So, lets take my same .38 SAC with a gauge that reads 2900, but is really filled to 3200, and breathe it down to 1000 psi, where the gauge will probably read more like 900 psi. Over the course of the dive, according to the gauge, I used 2000 psi, but with a proper gauge, I used 2200 psi. Lets see what happens when we change this variable. Instead of my proper .38 SAC, I really was breathing closer to .41 SAC... (well, not really, but for this demo)
So, as you can see, if you could stand to read that all, that it is very easy to manipulate your SAC just by changing the way you mentally read things...
Now, here is the deal - so long as you aren't coming back with headaches and such, you are probably breathing plenty. O2 uptake isn't typically a problem diving, as you could theoretically breathe in half as much at 10m/33 feet and still get enough O2, however, you won't get rid of nearly as much CO2 as you need to get rid of. How do we tell if you have too much CO2, well, headaches are one way, and maybe someone else will chime in with the other ways to tell. Aside from bragging rights, SAC isn't terribly important, so long as you are planning dives, following those plans, and watching NDL's a tad closer than the guy that breathes down a full AL80 at 30 feet in less than 30 minutes...
