The flammability limits are important to note, due to easy combustion or making safe mixtures. Optimum combustible mixtures are important for internal combustion engine's ignition. For example, lower flammability limit of Jet A fuel in the air at sea level is about 0.7%.

Why LFL and UFL is important?

As the amount of fuel continues to increase, the mixture will eventually become too rich to burn - there will be too much fuel and not enough Oxygen. ... Between the LFL and the UFL lies the flammable range where, given a source of ignition, the mixture will readily ignite.

What is meant by the term flammability limits?

Flammability limits or explosive range: The entire range of concentrations of a mixture of flammable vapor or gas in air (expressed as volume percent) over which a flash will occur or a flame will travel if the mixture is ignited.