When filling a cylinder by volume using a fixed maximum liquid level gauge, what does the process rely on to determine when to stop filling?

When filling a cylinder by volume using a fixed maximum liquid level gauge, the correct answer hinges on the operator’s role in monitoring the process. The gauge itself provides a visual reference to indicate the maximum liquid level, but it does not actively stop the filling process; it merely serves as a guide.

The operator's responsibility is to continuously observe the gauge and decide when the correct fill level has been reached. This requires diligence and understanding of the gauge's readings, as well as awareness of the cylinder's capacity, to ensure safe and accurate filling. The dependence on the operator underscores the importance of proper training and attentiveness when conducting LP-gas operations, emphasizing that human judgment is critical in the process.

The other options focus on the gauge, temperature, and pressure, which can influence filling but do not directly control or initiate the stopping of the fill process. While these factors are relevant in understanding how the system works, they do not replace the operator's crucial oversight in ensuring the cylinder is filled correctly without overfilling.