What does the term 'range of flammability' refer to?

The term 'range of flammability' specifically refers to the mixture of air and a combustible gas, such as LP gas (liquefied petroleum gas), that can readily ignite and sustain combustion. This concept encompasses the lower and upper limits of concentration in which the gas can mix with air and still continue to ignite. If the concentration of the gas falls below the lower limit or exceeds the upper limit, the mixture will not support combustion. This understanding is critical in various safety and regulatory contexts, particularly in handling and storing flammable materials, ensuring that operations stay within safe limits to prevent fires or explosions. The correct answer encapsulates this essential characteristic of flammable mixtures, highlighting its central role in fire safety management.