Abstract: On July 16, 2002, Employee #1, an electrician with Tobias Builders, was helping to replace old equipment in the main electrical room of the Nixon Elementary School in Cerritos, CA. The job was part of overall renovation and remodelling work underway during the summer vacation period. On the day before the accident, Employee #1 had discussed the first part of the job with his supervisor, which was to remove the electrical equipment from the east wall of the approximately 15 ft by 20 ft main electrical room. Shortly before 9:00 a.m., Employee #1 was in front of the 480-volt, 800-amp Zinsco switchgear, catalog #FDP 368T, on the east wall of the room. It had the meter section on the left-hand side (with the main disconnect), along with Southern California Edison's (SCE) feed. The right-hand load section had the following: (1) five disconnect switches (AC1 through AC5 for the air conditioning system and arranged in a vertical plane); (2) another disconnect for a transformer; and (3) the last disconnect switch (HA/HB), which was connected to other panels inside the building. Employee #1 turned each disconnect lever to switch off AC1 through AC5 and HA/HB. The transformer disconnect was not switched off, apparently to have power for other purposes while construction operations were underway. Immediately after turning off the switches, he started pulling the disconnected wire/cable ends of HA/HB from the conduit that was protruding at floor level. There was an instantaneous explosion/flash in front of Employee #1 from the right-hand side panel, AC3. He turned his face and stepped back, sustaining burns to his right hand and to the lower left side of his face. He was initially taken to La Palma Inter Community Hospital and was later transferred to Grossman Hospital at Sherman Oaks, where he was treated for three days. The cause of the accidnt was Employee #1's failure to disconnect/lockout the main SCE feed line on the meter section of the panel.