The potential for gas and dust explosions in the process industries has been historically recognized. Potentially explosible materials, both organic and inorganic, are handled in large quantities on a daily basis. These hazardous materials are processed in vessels and/or pipes: that is volumes with small length to diameter (L/D) ratios or volumes with large length to diameter ratios. It has also been historically recognized that explosions have different characteristics in different volumes. This difference becomes critically important when explosion protection methods are being designed.