a process method utilizing customized , specifically - shaped pieces of reticulated polyurethane foam to fill an aircraft fuel tank or tank compartment to provide ignition mitigation and prevent explosion in the tank . the process involves inserting the shaped pieces of rpf through existing access ports into a fuel tank in order to fill the tank , excepting minimal planned void spaces . this process effects ignition mitigation by acting as an ignition blocker , mechanically interfering with the compression wave that precedes the flame front in an explosion , and changing the vaporous mixture above the fuel level in the tank . the foam pieces are assembled and fitted together throughout the tank in a pattern that replicates the shape of the tank . after the foam insertion is complete , the fuel tank is filled with purging fluid , drained through a filter until no debris is found , and the new maximum fuel quantity is recalibrated .