Need to know your SAC rate?
Posted by sevenseas on 2021年5月30日
Hello divers! how are you all doing today?
Recently, I’ve been hearing from our guests that they consume too much air during dive and need to get better on it. Yes, I feel you. I’ve had that problem since the beginning of my diving career. My body generally needs more air than regular people do due to my body size, but I need to consume less air as an instructor and guide.
To improve your Air consumption, you need to know why you consume more air than others and how much air you actually use during dive.
First of all, there are so many factors to your Air Consumption. Here are some examples of the causes.
- stress
- exertion
- streamlining
- buoyancy
- coldness
Next, you would like to know your air consumption rate. To do so, we calculate Surface Air Consumption well know as SAC rate. Here are some information you need to know for the calculation.
- Cylinder size
- tart Air pressure
- End Air pressure
- Average Depth
- Dive Duration
Now, let’s practice the calculation.
Let’s assume a dive to a maximum 27 metres for 42 minutes on a 15 litre cylinder with a start pressure of 212 bar and an end pressure of 53 bar. The average depth for the dive is 21.56 metres.
- calculate the amount of gas used
212 bar – 53 bar = 159 bar used - multiply the amount of gas used by the size of the cylinder
159 bar x 15 litres = 2,385 litres of gas consumed - divide the amount of gas used (x the size of the cylinder) by the dive duration
2,385 litres / 42 minutes = 56.79 litres per minute - compensate for the average depth
the average depth of 21.56 metres now becomes 3.156 atmospheres for this calculation
56.79 litres per minute / 3.156 average depth = 17.99 litres per minute SAC Rate
As a result, this calculation gives us 17.99 litres per minute SAC Rate
We recommend you to do this calculation every time you dive and see how the rate changes. Then think why the rate changes. Stress? Tired? Too Cold?
Have a great diving! Dive more, Dive safe through education!!
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