The pressure gauge on an oxygen tank accurately reflects the amount of gas remaining.

• A. True
• B. False
• C. It depends on the cylinder size
• D. It reflects only the pressure, not the remaining volume

Answer: (A)

The gauge reading reflects how much gas is left because it measures the pressure inside the cylinder. In a fixed-volume container, the amount of gas (n) is directly related to pressure (P) at a given temperature: as you use gas, n decreases and the pressure drops. Therefore, a higher cylinder pressure indicates more gas remains, and a lower pressure indicates less. This makes the pressure gauge a practical, reasonably accurate indicator of remaining gas under normal storage and use conditions. Keep in mind that temperature changes or regulator nuances can cause small deviations, so for exact quantities you’d weigh the cylinder or use a conversion chart, but for everyday use the gauge is the standard indicator of remaining gas.