Your vessel has a gasoline engine and a mechanical exhaust ventilation system. BEFORE starting the engine, the exhaust blower should be run long enough to __________.

Correct Answer: Option A — insure at least one complete change of air in the compartments concerned

Gasoline vapors are heavier than air and accumulate in the bilge. Running the mechanical exhaust blower before starting the engine is a critical safety procedure required by 46 CFR to ensure at least one complete air change, effectively purging explosive vapors from the engine compartment to prevent ignition.