Medical Oxygen Cylinder Duration Calculator

The Virginia Department of Health's formula subtracts 200 psi from the gauge reading and calls the result the time until the cylinder is empty. 200 psi is about 14 bar, the figure used in metric mode. BOC's cylinder instructions say to consider a new cylinder when the gauge needle is in the red zone. The reserve can be switched off to see the full contents.

Enter the rate set on the flowmeter or written in the prescription. For reference, StatPearls gives nasal cannulas at 1 to 6 L/min, simple face masks at 5 to 10 L/min, and high-flow nasal cannulas at up to 60 L/min.

Both measure pressure, and 1 bar is about 14.5 psi. BOC's UK cylinders are rated in bar, while US guidance such as the Virginia formula uses psi. A 200 bar cylinder is roughly 2,900 psi, and 2,200 psi, the maximum fill StatPearls gives for US cylinders, is about 152 bar. Use the unit printed on the gauge.

The BOC sizes come from BOC's data sheet: CD holds 460 L at 230 bar, HX 2,300 L at 230 bar, and ZX 3,040 L at 300 bar. The US factors come from the Virginia Department of Health. The 10 L and 40 L presets assume a 200 bar fill; for any other cylinder, read the water capacity and fill pressure off its label and use Custom.

Metric mode treats the oxygen left as water capacity × pressure, and US mode as psi × factor. Real cylinders differ slightly: BOC rates its 10 L ZX at 3,040 L at 300 bar, a little more than 10 × 300 = 3,000 L. Gauge accuracy and changes to the flow rate also affect how long a cylinder lasts.

No. It is an estimate to support — not replace — clinical assessment, the facility's protocols, and direct reading of the cylinder gauge. Gauge accuracy and any change in the flow rate will change how long the cylinder actually lasts.

Cylinders with an integral valve, such as BOC's CD and HX, have a contents gauge at the top that BOC says shows gas levels even when the cylinder is switched off. Cylinders without one need a regulator with a pressure gauge fitted.