MIE is defined as what?

• A. The lowest temperature at which a material will spontaneously ignite and continue burning in a normal atmosphere
• B. The minimum energy required to ignite a combustible vapor, gas or dust cloud
• C. The highest concentration of a substance in air that will sustain combustion
• D. The minimum oxygen concentration required to propagate a flame

Answer: (B)

Minimum Ignition Energy is the least amount of energy that must be transferred to a combustible mixture in air to start combustion. It shows how easily a spark, heat burst, or static discharge can ignite a vapor, gas, or dust cloud. A lower MIE means the mixture is more easily ignitable, so smaller energy sources can cause ignition, while a higher MIE requires a stronger energy input. This concept is distinct from the autoignition temperature, which is the temperature at which a material will ignite without any external ignition source, and from flammable-range limits or oxygen requirements, which describe concentration and oxidizer needs rather than the energy needed to start burning.