Who is permitted to leave the building refrigeration system when it is in operation?

The correct choice pertains to safety and operational protocols surrounding the handling of building refrigeration systems. Only a licensed refrigeration engineer who is adequately trained and aware of the operational status and safety measures can leave the system running without supervision. This ensures that there is always a qualified individual responsible for monitoring the system, which is essential for preventing accidents or malfunctions.

Leaving a refrigeration system in operation must be done with care. If one licensed engineer is relieved, another licensed engineer must take over the responsibilities to ensure that the system is managed properly. This practice maintains adherence to safety standards and operational guidelines, which is crucial in preventing potential issues such as equipment failure or hazardous situations.

Other options may suggest allowing various personnel to leave the refrigeration system in operation, but without a licensed engineer present when one leaves, the risk of mismanagement or overlooking critical monitoring can increase significantly, which is why those options do not align with safety protocols.