What exactly is SAC?

[beejw]

I did ... but nothing come up.

Best i came up with was Submerged Air Consumption?
IS this right?

if no, what is?

cheers,
Beej.

 

[drew52]

surface air consumption

 

[beejw]

okay...so how does that realte to diving and why is it so important?

 

[Scuba_Steve]

okay...so how does that realte to diving and why is it so important?

Better search procedure required. There's gotta be 1000's on this board. Here's one, with several more at the bottom of that page.

http://www.scubaboard.com/showthread.php?t=169737&highlight=sac+rate+air+consumption

 

[pir8]

If you know your SAC you can calculate how long your tank will last at depth

 

[Mrs.Prages]

Try this link -

http://www.scubaboard.com/archive/index.php/t-476.html

SAC Rates can be very important for dive planning and safety.

 

[The Kraken]

SAC is "surface air comsumption". It is usually expressed in cubic feet per minute.
It is the amount of air one consumes at 1 ATA, or at the surface, if you would.
Keep in mind that, while your SAC may remain the same, the VOLUME of air you consume will increase as you go deeper. The volume consumed is directly proportional to your depth expressed in ATA's.

Let us suppose your SAC rate is 0.5 cubic feet per minute.
All other things remaining equal . . .
At the surface you will consume 1/2 cubic feet of air per minute.
At 33' (2 ATA) you will consume 1 cubic foot of air per minute.
At 66' (3 ATA) you will consume 1.5 cubic feet of air per minute, and so on.

 

[Guba]

And I have a question to add to the original...(showing my ignorance).
What is the best way to ascertain one's SAC rate? I know only one way, and it seems a bit cumbersome. I'm looking to upgrade the procedure, if you know what I mean.
Much obliged to anyone who can fill me in.

 

[Thalassamania]

And I have a question to add to the original...(showing my ignorance).
What is the best way to ascertain one's SAC rate? I know only one way, and it seems a bit cumbersome. I'm looking to upgrade the procedure, if you know what I mean.
Much obliged to anyone who can fill me in.

Record your starting and ending pressures, times, tank size and depth for several "squarish" dives and calculate it.

 

[drew52]

total air used divide dive time divide average depth

Using the Metric System:
start with 200 bar end with 100 bar therefore I used 100 bar; using 12l cyliner so 100bar x 12 = 1200 liters of air

1200 divide 40minutes (dive time) = 30 divide 3 (average depth in ata) (20m in ata is 3) = 10l/min

If you don't know average depth then take max depth but this is less accurate.