Abstract: On February 3, 1995, Employee #1 and a coworker were working on the vacuum extraction of a catalyst from the unit 152 regenerator. They were on the fourth level deck. The regenerator manway door had been opened, showing a high catalyst bank sloping from the doorway back to the regenerator. The vacuum hose was inserted into the regenerator and extraction started. On February 4, 1995, extraction from the manway on the fourth level continued. Around 4:30 p.m., the employees briefly heard a loud sound and saw a momentary bright red glow that left white dusty catalyst powder sprayed all over. Employee #1 and his coworker had just taken off their thermal mittens and consequently suffered severe hand burns and some neck burns. Employee #1 was taken to Kaiser and then Torrance Memorial Hospital. The cause of the accident may be traced to Employee #1's injecting air from the bottom of the regenerator; firebricks falling onto the catalyst; or the vacuum extraction regenerator catalyst level suddenly folding back, giving rise to the catalyst cloud.