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Cornell Pediatrics

Oxygen Tank Duration

Estimate the time that an oxygen cylinder will support delivery of gas at a particular flow, or estimate the pressure in an oxygen cylinder that will support a particular flow for a particular duration. These calculations apply not only to oxygen but for other gases.

Name (Dimensions)
D  (4" x 16")
E  (4" x 26")
M  (8" x 36")
H  (9" x 52")
Safe Residual Pressure   PSI  
Input Flow  LPM  

Input one of the following:
Duration  minutes
Gauge Pressure  PSI



The calculations are based on Boyle's law that states that pressure and the volume of a given amount of a confined gas are inversely proportional (P * V = k).

Duration  =  
k * (P - R)

Pressure  =  
T * F
+ R

k is the tank constant in PSI-1 liters-1.
R is the Safe Residual Pressure in PSI, typically 200 PSI.
F is the Flow in liters per minute.
T is the duration in minutes.
P is the tank gauge pressure in PSI.

Instructions: Pick the tank and enter the desired flow. Then, either

  1. enter the duration of the trip and click on the Calculate Pressure button to get the tank pressure required, or
  2. enter the gauge pressure and click on the Calculate Duration button to calculate how long that tank will last.

For example, a respiratory therapist wants to make sure the patient on heliox (H cylinder) running at 10 LPM will not run out of gas over the change of shift. The gauge reads 600 PSI. Entering these data and hitting Calculate Duration yields a duration of 126 minutes.


Created: February 22, 2013
Revised: February 22, 2013

Weill Medical College of Cornell University
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