The Minimum Explosible Concentration (MEC) test provides a measure of the smallest dust cloud concentration that is necessary for a deflagration to occur. A successively smaller quantity of dust is dispersed in a 20-Liter spherical vessel and each time an attempt is made to ignite the dust cloud with an energetic chemical ignitor. The smallest dust cloud concentration that is necessary for a deflagration is defined as the MEC. Since MEC may vary with the uniformity of the dust dispersion, energy of the ignitor, and propagation criteria, MEC should be considered a relative rather than absolute measurement.

The MEC test is performed in accordance with the requirements of the current edition of the American Society for Testing and Materials (ASTM) E1515.