When should a power ventilation system be turned on for a vessel?

The power ventilation system of a vessel should be turned on after fueling or before starting the engine to ensure safety and minimize the risk of fire or explosion. This is crucial because the process of fueling can release flammable vapors into the air, which can accumulate in the confined spaces of the boat. By activating the ventilation system, these vapors can be expelled, creating a safer environment before any ignition sources, like the engine, are started. This preventive measure is essential for maintaining a safe atmosphere in the vessel.

Turning on the ventilation system during docking, after a storm, or before anchoring does not specifically address the immediate risks posed by flammable vapors resulting from fueling, making these options less appropriate in the context of safety concerning fueling practices.