The pressure of gas in a full cylinder of oxygen is approximately ______ psi.

• A. 3,000
• B. 1,000
• C. 2,000
• D. 500

Answer: (C)

Oxygen is stored as a high-pressure gas in a cylinder, so the gauge on a standard medical cylinder reflects a high internal pressure when full. For a typical full cylinder, the pressure reads about two thousand pounds per square inch. That high pressure corresponds to the large amount of gas stored in a fixed-volume container. As you start delivering oxygen, the gas leaves the cylinder and the pressure drops on the gauge, signaling how much is left. The regulator then steps the pressure down to a safe, usable level for patient delivery, but the cylinder’s remaining-pressure gauge is the quick way to estimate fullness.

That’s why two thousand psi is the best answer. A figure around three thousand psi would be higher than what a full medical cylinder usually holds. About a thousand psi would indicate a partially used cylinder, not full, and five hundred psi is typically near empty. In practice, you use the gauge to decide when to replace or refill, knowing full is around 2000 psi.