Abstract: A MAINTENANCE WORKER WAS ASSIGNED TO CHECK A 240-VOLT ELECTRIC SWITCH THAT WAS NOT MAKING PROPER CONTACT. THE SWITCH WAS MOUNTED IN A FEDERAL PACIFIC PANELBOARD (SERIAL NUMBER AJ-316403, 1200 AMPERES; BOTTOM SECTION: SERIAL NUMBER QMQB 1032). THE PANELBOARD WAS 36 INCHES WIDE BY 84 INCHES TALL WITH SIX SWITCHES MOUNTED INSIDE. THE BOTTOM SECTION OF THE PANELBOARD WAS 18 INCHES WIDE BY 6 INCHES TALL AND WAS 18 INCHES ABOVE THE GROUND. THE MAINTENANCE WORKER OPENED THE SWITCH AND THEN OPENED THE DOOR OF THE PANELBOARD. AS HE WAS OPENING THE DOOR, ONE OF THE PHASE CONNECTORS FELL AND CONTACTED ANOTHER PHASE, RESULTING IN AN ELECTRICAL EXPLOSION. (IT IS BELIEVED THAT CONTINUED SHAKING OF THE SWITCH CAUSED VIBRATIONS THAT LOOSENED THE CONNECTOR.) THE MAINTENANCE WORKER RECEIVED FIRST AND SECOND DEGREE BURNS ON HIS RIGHT SHOULDER, RIGHT ARM, AND FACE, AND HE RECEIVED THIRD DEGREE BURNS ON HIS RIGHT HAND. THE EMPLOYEE WAS HOSPITALIZED FOR HIS INJURIES.