Oxygen Cylinder Duration & Flow Calculator
D Cylinder (0.16)
E Cylinder (0.28)
M Cylinder (1.56)
G Cylinder (2.41)
H/K Cylinder (3.14)
Estimated Duration
How to Calculate Oxygen Cylinder Duration
Calculating the duration of an oxygen tank is a critical skill for emergency medical technicians (EMTs), paramedics, and respiratory therapists. The "flow rate" determines how much oxygen is delivered to the patient per minute, while the tank's pressure and size determine the total volume available.
The Formula
Duration (Minutes) = [(Tank Pressure – Safe Residual) × Cylinder Factor] / Flow Rate
Understanding the Variables
- Tank Pressure: The current PSI reading from the regulator gauge. A full tank is typically around 2000-2200 PSI.
- Safe Residual: The safety margin (usually 200 PSI) to ensure the tank never runs completely empty, which prevents moisture from entering the cylinder.
- Cylinder Factor: A constant based on the physical size of the tank (e.g., E-cylinders are 0.28).
- Flow Rate: The liters per minute (L/min) prescribed or required for the patient (e.g., 2 L/min via nasal cannula or 15 L/min via non-rebreather mask).
Common Oxygen Cylinder Factors
| Cylinder Type | Constant / Factor |
|---|---|
| D Cylinder | 0.16 |
| E Cylinder | 0.28 |
| M Cylinder | 1.56 |
| G Cylinder | 2.41 |
| H or K Cylinder | 3.14 |
Example Calculation
If you have an E-cylinder with 1200 PSI and the patient is receiving 10 L/min via a non-rebreather mask, the calculation would be:
- Subtract residual: 1200 – 200 = 1000 PSI
- Multiply by factor: 1000 × 0.28 = 280
- Divide by flow: 280 / 10 = 28 minutes