The chemical bond attaching the elastic neck seal to the body of the protective breathing equipment (PBE) procured by the U.S. Air Force as an emergency passenger oxygen System (EPOS) was alleged to be inadequate to allow the PBE to perform as intended at altitude. To test this possibility, EPOS units were collected from Air Force Bases and systematically tested at altitude. The Civil Aerospace Medical Institute was requested to participate in the testing through the FAA Office of the Inspector General and the U.S. Air Force's Office of Special Investigations due to the Institute's longstanding expertise in the area of PBE.