FAQ Level 3 Award for First Responders on Scene: Emergency First Responder (RQF) FROS® - Online Blended Part 1

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How long does an Oxygen cylinder last?

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Calculating Oxygen Cylinder Duration

Planning Oxygen Usage

Determining How Long Your Oxygen Cylinder Will Last

Using the Cylinder Duration Formula

Estimating Oxygen Supply Time

  • Step 1: Cylinder Pressure
    • Locate the cylinder pressure (psi).
    • Subtract a residual pressure of 200 psi to account for errors.
  • Step 2: Cylinder Constant
    • Refer to the cylinder constant values:
    • "D" cylinder: Constant = 0.16
    • "E" size: Constant = 0.28
    • "M" size: Constant = 1.56
    • "G" size: Constant = 2.41
    • "H" and "K" size: Constant = 3.14
    • Choose the constant based on your cylinder size.
  • Step 3: Flow Rate
    • Determine the flow rate in litres per minute.
    • Typically, regulators provide a maximum of 15 litres per minute.
    • Specialist applications may have higher flow rates (e.g., scuba diving, 25 litres per minute).
    • Adjust the flow rate as needed (e.g., 6 litres per minute for a nasal cannula).
  • Step 4: Calculate Duration
    • Use the formula: (Tank pressure - Residual pressure) x Cylinder constant / Flow rate
    • Calculate the time in minutes that the cylinder will last.

Example Calculation

Estimating Duration for a "D" Cylinder at 15 Litres Per Minute

  • Step 1: (2000 psi - 200 psi) = 1800 psi
  • Step 2: Cylinder Constant for "D" size = 0.16
  • Step 3: Flow rate = 15 litres per minute
  • Step 4: (1800 psi x 0.16) / 15 litres per minute = 19.2 minutes
  • Estimated Duration: Approximately 19 minutes (rounded down)

Use this formula to calculate the duration of your oxygen cylinder based on your specific parameters.