What is the lower flammability limit of propane vapor?

The lower flammability limit (LFL) of propane vapor is crucial to understanding its flammability and safety in various applications. The LFL represents the minimum concentration of propane in air below which it will not ignite. For propane, this limit is approximately 2.15% by volume in air.

This specific concentration is essential for safety practices in handling, storing, and using propane, as concentrations below this level will not support combustion, significantly reducing the risk of fire or explosion in environments where propane might be used. Knowing the LFL helps to ensure that safety measures are implemented correctly to prevent accidental ignition scenarios.

The other choices provided do not accurately reflect the scientifically established LFL for propane, thus they cannot be considered correct.