What is the surface air consumption rate (SAC) of a diver using a 3000 psi-rated, 80-cubic foot cylinder, using 650 psi in 10 minutes at a depth of 33 feet?

To determine the surface air consumption rate (SAC) for the diver, it's essential to calculate how much air is consumed per minute and then adjust that for the effective pressure at a depth of 33 feet.

First, calculate the total amount of air consumed during the dive. The diver started with 3000 psi and ended using 650 psi, which means they used:

3000 psi - 650 psi = 2350 psi

Next, since the diver was underwater at a depth of 33 feet, it’s important to understand that this depth corresponds to a pressure of approximately 2.1 atmospheres (1 atmosphere for the surface and about 1.1 atmospheres for the additional water pressure at this depth).

To convert the consumed psi at the depth of 33 feet into a surface equivalent, divide the used pressure by the total pressure at that depth. Therefore, the effective surface consumption can be calculated as follows:

2350 psi / 2.1 atm ≈ 1119.05 psi (surface equivalent)

Now, since this amount of air was consumed over a timeframe of 10 minutes, we can find the SAC rate:

1119.05 psi / 10 minutes ≈ 111.9 psi/minute