Before starting gasoline engines, what should be done to ventilate the engine space?

• A. Run the exhaust blower for at least four minutes prior to starting the engine.
• B. Open hatches to ventilate.
• C. Start engine immediately with no ventilation.
• D. Ventilate only after the engine is started.

Answer: (A)

Gasoline engine spaces can accumulate flammable vapors, and those vapors can ignite if a spark or hot surface is present. To prevent this, you need forced ventilation before ignition. Running the exhaust blower for at least four minutes pushes vapors out of the engine space and brings in fresh air, reducing the vapor concentration to a safer level prior to starting the engine. Opening hatches alone helps but may not remove vapors quickly enough, and starting the engine without ventilation or ventilating only after starting creates a real ignition risk. This four-minute blower pre-ventilation is the proper precaution.