Question 1

What is a good SAC rate for a scuba diver?

Accepted Answer

A "good" Surface Air Consumption (SAC) rate typically falls between 12–15 liters per minute (0.4–0.5 cu ft/min) for experienced divers in relaxed conditions. However, beginners or divers in cold water often have rates between 20–25 L/min. Lowering your SAC rate improves gas autonomy and is achieved through buoyancy control and streamlining.

Question 2

Why is the Ideal Gas Law inaccurate for scuba calculations?

Accepted Answer

The Ideal Gas Law ($PV=nRT$) assumes gas molecules have no volume and do not interact, which causes calculation errors at high pressures (like in a full scuba tank). Real gases compress differently; our calculator uses the Compressibility Factor ($Z$) and Van der Waals equations to account for the non-linear behavior of air and Nitrox at 200+ bar, providing a scientifically accurate SAC rate.

Question 3

How does tank material (Steel vs. Aluminum) affect air calculations?

Accepted Answer

While the material doesn't change the air, the rated volume does. Aluminum tanks (like AL80s) are often rated at their working pressure, whereas steel tanks use actual internal volume. An accurate SAC calculation must distinguish between "rated capacity" and "internal water volume" to determine the true volume of gas consumed.

Question 4

Does diving with Nitrox change my air consumption rate?

Accepted Answer

Physiologically, breathing Nitrox does not significantly change the volume of gas you inhale per minute compared to air. However, because Oxygen and Nitrogen have slightly different densities and compressibility factors, a high-precision calculation (like the one used in this tool) adjusts for the specific gas mixture density to give the truest respiratory minute volume (RMV).

Surface Air Consumption (SAC) calculator

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