What is the term for the range in which combustion can occur based on fuel vapor and air concentration?

The term that describes the range in which combustion can occur based on the concentration of fuel vapor and air is known as the flammable range. This range defines the specific limits—the lower and upper explosive limits—within which the fuel vapor can ignite when mixed with air. If the concentration of fuel is below the lower limit, there isn't enough fuel to sustain combustion; if it exceeds the upper limit, there’s insufficient oxygen available for ignition. Understanding this range is essential for effective fire prevention and firefighting, as it helps identify conditions under which fire hazards are present.

In contrast, the other terms have distinct meanings related to fire safety and combustion but do not specifically refer to the concentration range for ignition. The flash point refers to the lowest temperature at which a substance will produce enough vapor to ignite, while the explosive range and combustible range are less commonly used and may sometimes overlap with but do not specifically delineate the parameters for ignition as clearly as the flammable range does.