Arrange the following oxygen delivery devices from lowest to highest typical FiO2 range.

• A. Simple face mask → Nasal cannula → Non-rebreather mask
• B. Non-rebreather mask → Simple face mask → Nasal cannula
• C. Nasal cannula → Simple face mask → Non-rebreather mask
• D. Nasal cannula → Non-rebreather mask → Simple face mask

Answer: (C)

Understanding how much oxygen each device can deliver helps you match the device to the patient’s needs. A nasal cannula provides the lowest FiO2, about 24–44%, and is limited by how much ambient air mixes with the delivered O2. A simple face mask raises FiO2 to roughly 40–60%, though its actual value can vary with the fit and whether the patient breathes through the nose or mouth. The non-rebreather mask can reach the highest FiO2, up to about 100% with a properly filled reservoir and a tight seal, though practical delivery often falls in the 60–100% range depending on flow and fit. Because of this progression, the order from lowest to highest typical FiO2 is nasal cannula, then simple face mask, then non-rebreather mask.