🔍 Key Concepts

• Flammable limits of oil mist in air (lower explosive limit and upper explosive limit) • How concentration affects the violence of an explosion compared to just ignition • Relationship between an air-fuel mixture being too lean, ideal, or too rich to support maximum explosion pressure

💭 Think About

• Think about where, between very low and very high concentrations, a fuel-air mixture usually produces the greatest explosion pressure. • Consider what happens if the mixture is below the lower explosive limit (too lean) or above the upper explosive limit (too rich) – will it burn at all, and if so, how violently? • Compare each option to the typical range where hydrocarbon mists or vapors have their most efficient combustion and see which is closest.

✅ Before You Answer

• Identify which ratio range is likely within the flammable limits for oil mist in air, not too lean and not too rich. • Ask yourself: which option falls near the middle of the flammable range, where combustion is usually most complete and pressure rise is greatest? • Verify that the chosen option represents a mixture that would support rapid flame propagation rather than weak burning or no ignition.