Under what circumstances would you only lower the vent flap lever?

The correct context for only lowering the vent flap lever pertains to specific weather conditions or situations involving "Remain Over Night" (RON) aircraft operations. Lowering the vent flap lever in these circumstances helps manage cabin temperature and ventilation while ensuring that the aircraft is prepared for optimal performance during extended ground times or when adverse weather conditions might affect the interior environment.

When the ambient conditions call for better airflow or adjustment of temperature control, simply lowering the vent flap lever can address these concerns without needing to apply other operational parameters that might be required during takeoff, at high altitudes, or at the direction of cabin crew. This action serves a particular purpose related to maintaining cabin comfort and is a critical procedure in those specified scenarios.