What is the formula used to calculate the duration of an oxygen tank?

The formula for calculating the duration of an oxygen tank is structured to incorporate the tank's gauge pressure, the tank constant, and the flow rate. In option B, the calculation correctly reflects the way gas flow and remaining pressure influence the duration of oxygen supply.

The gauge pressure in psi indicates how much oxygen is left in the tank. By subtracting 500 psi from the gauge pressure, we account for the pressure below which the tank is generally considered empty, ensuring that only the usable portion of the gas is factored into the duration calculation.

The tank constant represents the volume of the tank at a specific pressure, essentially linking the pressure to the amount of oxygen available. Dividing this amount by the flow rate yields the duration in minutes that the oxygen can be supplied at that flow rate.

This combination enables healthcare professionals to estimate how long a supply of oxygen will last for a patient based on the pressure remaining in the tank and the required flow rate.