The second-stage O2 pressure regulator delivers a constant O2 pressure to the rotameters of approximately:

The second-stage O2 pressure regulator delivers a constant O2 pressure to the rotameters of approximately:

• A. 4 psi
• B. 8 psi
• C. 16 psi
• D. 32 psi

Answer: (C)

Rotameters rely on a fixed upstream pressure to give an accurate reading of flow. The second-stage O2 regulator is there to provide a stable, low pressure to the rotameters so the float height (and thus the indicated flow) stays consistent regardless of small changes in supply or downstream resistance. That stable pressure is about 16 psi. Maintaining roughly 16 psi upstream of the flowmeters ensures the flow readings are reliable and proportional to how you open the control valve, across the full range of intended flows. If the pressure were much lower, high flow settings would be less accurate; if it were much higher, the readings could become misleading and the system could deliver more gas than planned. 16 psi hits a practical middle ground: enough to drive flow through the rotameters across the typical 0–15 L/min range, while staying safely within the design of the low-pressure system.

Rotameters rely on a fixed upstream pressure to give an accurate reading of flow. The second-stage O2 regulator is there to provide a stable, low pressure to the rotameters so the float height (and thus the indicated flow) stays consistent regardless of small changes in supply or downstream resistance. That stable pressure is about 16 psi. Maintaining roughly 16 psi upstream of the flowmeters ensures the flow readings are reliable and proportional to how you open the control valve, across the full range of intended flows.

If the pressure were much lower, high flow settings would be less accurate; if it were much higher, the readings could become misleading and the system could deliver more gas than planned. 16 psi hits a practical middle ground: enough to drive flow through the rotameters across the typical 0–15 L/min range, while staying safely within the design of the low-pressure system.