Oxygen Tank Duration
All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.
Estimate how long a gas cylinder will last at a given flow rate, or determine the minimum starting pressure needed for a given duration. Applies to oxygen, air, heliox, and other compressed gases.
| Tank (dimensions) | k (PSI−1 L−1) | Capacity (L) |
|---|---|---|
| 0.16 | 340 | |
| 0.28 | 625 | |
| 1.56 | 3,450 | |
| 3.14 | 6,900 |
Enter one of the following and click its button:
The calculations are based on Boyle's Law, which states that the pressure and volume of a confined gas at constant temperature are inversely proportional (P × V = constant). The tank constant k (in PSI−1 L−1) encodes the cylinder's physical volume:
Pressure required = D × F k + R
where P is gauge pressure (PSI), R is safe residual pressure (PSI, typically 200), F is flow rate (LPM), T is duration (min), and k is the tank constant.
The safe residual pressure (200 PSI by default) is the pressure at which the tank should be considered empty for planning purposes, as flow may become unreliable below this level.
These formulas apply equally to oxygen, heliox, air, nitric oxide, and other compressed gas cylinders — substitute the appropriate tank constant.
Standard tank reference data:
| Tank | Dimensions | k | Capacity (L) | Full pressure (PSI) |
|---|---|---|---|---|
| D | 4″ × 16″ | 0.16 | 340 | 2,015 |
| E | 4″ × 26″ | 0.28 | 625 | 2,015 |
| M | 8″ × 36″ | 1.56 | 3,450 | 2,015 |
| H/K | 9″ × 52″ | 3.14 | 6,900 | 2,015 |
References
- Compressed Gas Association. Handbook of Compressed Gases. 4th ed. Kluwer Academic Publishers; 1999.
- Walsh BK, Crotwell DN, Restrepo RD. Capnography/capnometry during mechanical ventilation: 2011. Respir Care. 2011;56(4):503–509.