What term describes the percentage of a substance in air that will burn once it is ignited?

The flammable or explosive range refers to the specific concentration of a substance in air that will support combustion once ignited. This range is defined by the lower and upper limits of concentration for a particular fuel in air; if the concentration is below the lower limit, it is too lean to ignite, while if it exceeds the upper limit, it becomes too rich. Therefore, the flammable/explosive range is essential for understanding which conditions will allow a fire to start and sustain itself.

In contrast, the other terms do not accurately define the specific concept related to the percentage of a substance that will burn. While combustion threshold might refer to the minimum conditions required for combustion to occur, it does not specifically address the concentration in the air. Ignition mixture could imply a combination of substances needed to ignite, but it lacks the precise focus on percentage composition. Oxidation point relates to the point at which a substance will begin to oxidize, but again, does not describe the burning concentration in air. Thus, flammable/explosive range is the term that best captures this concept.