🔍 Key Concepts

• Understand what flammable (explosive) limits mean for vapors in air • Typical lower flammable limit (LFL) and upper flammable limit (UFL) ranges for common ketone solvents (like acetone and MEK) • How very high LFL values compare to what’s normally seen in practice

💭 Think About

• First, think about whether methyl ethyl ketone is considered easily ignitable at fairly low vapor concentrations or only at very high ones • Compare each option’s lower limit: which one best matches a solvent that can catch fire from relatively low vapor levels in air? • Then compare each option’s upper limit: does it make sense that vapors would still burn at that high a concentration, or would the mixture become too rich to burn?

✅ Before You Answer

• Check which choice has a realistic lower flammable limit (LFL) for a volatile solvent (usually in the low single‑digit percent range) • Eliminate any options where both limits are unusually high, since common liquid solvents don’t require such rich mixtures to ignite • Confirm that the chosen range is not too narrow, since many common solvents have a reasonably broad flammable range in air