How long will a 50 cu ft tank last at a depth of 72' breathing 1 cu ft per minute?

To determine how long a 50 cu ft tank will last at a depth of 72 feet while breathing at a rate of 1 cu ft per minute, we must first recognize that the volume of gas available in the tank is 50 cubic feet.

At a depth of 72 feet, the pressure increases due to the weight of the water above and is approximately 3.1 atmospheres (1 atmosphere at sea level plus 2.1 from the water depth). The effective volume of air that can be used from the tank is thus less than 50 cu ft because of the increased pressure. To find the effective volume of air, we need to adjust for the pressure:

Effective volume = Tank volume / Absolute pressure.

Calculating it gives us:

Effective volume = 50 cu ft / 3.1 atm = approximately 16.13 cu ft.

Now, if a diver breathes 1 cu ft per minute, we can find out how long the air will last:

Time = Effective volume / Breathing rate = 16.13 cu ft / 1 cu ft per minute = approximately 16.13 minutes.

Here, the answer of 30 minutes appears to reflect a misunderstanding, as it does not take into