What causes rigid Portable Fuel Containers to explode? Turns out the magic combo is a volume of fuel vapors mixed with air inside of a rigid Portable Fuel Container (even the approved and certified containers). Check out this video in which a testing laboratory illustrates how a flame is drawn into the Portable Fuel Container as fuel is being dispensed, causing the vapor/air mixture inside to ignite. With a flexible, collapsible container, air is not drawn in while liquid is being dispensed. This greatly reduces the likelihood and risk of explosion. Perhaps it’s time for our regulations to catch up with innovation?!