🔍 Key Concepts

• explosion relief valves on engine crankcases and gear/chain cases • volume thresholds in cubic feet vs cubic meters in safety regulations • conditions that actually cause crankcase explosions (oil mist ignition)

💭 Think About

• Think about whether regulations usually trigger safety devices based on operating conditions (like overload) or on fixed design parameters (like space volume). • Compare the choices that mention volume: do they describe the same size in different units, or are they clearly different thresholds? • Ask yourself what typically builds up inside a crankcase or gear case that could explode: is it "volatile gases" from cargo/atmosphere, or something else related to lubricating oil and temperature?

✅ Before You Answer

• Check which options give a clear, measurable design criterion that a surveyor or shipyard could easily verify. • Verify whether 21 cubic feet and 0.6 cubic meters are roughly the same size or significantly different (do the unit conversion in your head). • Eliminate any choices that rely on temporary operating conditions rather than permanent design features for fitting explosion relief devices.