🔍 Key Concepts

• Explosive (flammable) range of a vapor/air mixture • Difference between flash point, fire point, and ignition temperature • Meaning of lower vs upper limits for flammable vapors

💭 Think About

• Think about what happens as vapor concentration increases from very low to very high—at which range can an explosion actually occur? • If there is a lower explosive limit, what is the natural term for the concentration at the other end of that explosive range? • Which of the options are about temperatures and which are about concentration limits of vapors in air?

✅ Before You Answer

• Identify which choice refers to a concentration limit, not a temperature property. • Make sure you can define flash point and fire point and see why they are not the other boundary of the explosive range. • Confirm that the explosive range is always described as lying between two percentage-by-volume limits in air.