How much gas volume does a diver use at 90 fsw for 20 minutes?

To determine how much gas volume a diver uses at 90 feet of seawater (fsw) for 20 minutes, it’s important to consider the depth and the corresponding pressure, which influences gas consumption.

At 90 fsw, the ambient pressure is approximately 4.0 atmospheres (3.0 atmospheres for the water above, plus 1.0 atmosphere for surface pressure). This increased pressure means the diver is living in conditions where the volume of air consumed increases significantly compared to surface conditions.

To calculate the volume of gas used, divers typically refer to their air consumption rate, which can be expressed in terms of cubic feet per minute (cfm). A typical average consumption rate for a diver under moderate activity conditions at depth might be around 0.5 to 1.0 cfm. However, for depth calculations like this, it's common to take a more conservative estimation around 0.5 cfm under pressure.

For a diver breathing at 90 fsw for 20 minutes at an average rate of 0.5 cfm, the calculation follows these parameters:

1. Total cubic feet consumed at surface pressure:

0.5 cfm * 20 minutes = 10 cubic feet

2