Fuel oil tank vents are fitted with a screen which will stop __________.

Correct Answer: Option B — flames on deck from entering the tank vent

Flame screens are designed to act as a heat sink, quenching a flame front before it can propagate into a tank containing flammable vapors. Per 46 CFR, these screens prevent external ignition sources, such as deck fires or sparks, from entering the tank through the vent system.