A minimum-ignition-energy testing apparatus includes a combustion tube and a bottom assembly coupled to a lower end of the combustion tube. A top assembly is coupled to an upper end of the combustion tube. The top assembly includes a first sparge plate coupled to the top base plate. The first sparge plate has a first aperture formed therein. The top assembly also includes a second sparge plate coupled to the first sparge plate. The second sparge plate has formed therein a second aperture that aligns in registry with the first aperture. A channel is formed in the second sparge plate about a perimeter of the third aperture. The channel has a plurality of holes disposed therein that are formed through a thickness of the second sparge plate. A tube is formed through in the second sparge plate, the tube fluidly coupling the channel to a gas source.