When filling a cylinder by volume, the cylinder will be full when ________.

• A. White mist begins to escape from the fixed maximum liquid level gauge
• B. The gauge reads full
• C. The pressure is at maximum
• D. The valve closes automatically

Answer: (A)

Filling by volume relies on the fixed maximum liquid level gauge as the stop signal. When white mist begins to escape from that gauge, it shows the liquid level has reached the top limit of the gauge, so the cylinder is considered full. Venting at that moment prevents overfilling because any further fill would push liquid into the vapor space. The other signs aren’t reliable indicators: the gauge reading full can be affected by temperature or gauge design, pressure being at a maximum doesn’t guarantee the liquid level is at the top, and relying on the valve to close automatically isn’t a universal or dependable cue across setups.