What is the main disadvantage of using Independent Service in a fire situation?

In a fire situation, the main disadvantage of using Independent Service is that doors fully open automatically upon arrival. This feature can pose a significant risk in emergencies as it allows for potentially uncontrolled access to the elevator lobby and the building while the fire and smoke may be present. This kind of automatic function does not account for the current conditions outside the elevator, which can jeopardize the safety of both firefighters and civilians.

While it is beneficial for aiding in the rapid evacuation of individuals who may require assistance, the automatic door opening can create a hazardous situation where firefighters could inadvertently expose themselves to fire or smoke conditions. This action could lead to confusion and panic among building occupants.

In contrast, the other options either limit the control of the firefighters over the elevator (such as inability to respond to priority calls or inability to control the elevator directly) or simply discuss availability, rather than addressing the direct safety concern posed by the automatic door function in an active fire scenario.