The MIE of a substance is the Minimum Ignition Energy needed in order to ignite a flammable substance with air or oxygen, measures by a standard procedure.
Depending on the specific application, there are several standard procedures for determining MIE of dust clouds, solvent vapours and gases.
The common element in all procedures is that the energy is generated by an electrostatic spark discharge released from a capacitive electrical circuit. The exact circuit components and the arrangement of electrodes between which sparks are generated are the principle differences between the methods.
A list with MIE values of a series of substances can be downloaded here: MIE-list.pdf