What is the output pressure range of the oxygen reducer?

• A. 55-75 psi
• B. 10-207 BAR
• C. 0-5 psi
• D. 100-120 psi

Answer: (A)

The key idea is that the oxygen reducer provides a stable, manageable intermediate pressure to feed oxygen into the closed-circuit loop. It takes the high-pressure O2 from the cylinder and lowers it to a narrow, controllable range that the O2 injection valve and control system can regulate reliably as you change depth. Around fifty-five to seventy-five psi is chosen because it is high enough to push O2 into the loop against backpressure but low enough to be precisely controlled and to minimize the risk of overshooting the desired oxygen partial pressure. If the output were much higher, you'd risk delivering too much O2; if it were much lower, the system might not overcome backpressure and the O2 flow would be unstable, affecting PPO2 stability. The other options don’t fit because they either imply pressures unsuitable for reliable injection (too low, or too high) or use units not standard for this feed stage.