Abstract: THREE EMPLOYEES WERE WORKING IN A TRANSFORMER VAULT. TWO OF THEM HAD OPENED A LARGE NETWORK PROTECTOR BOX ON A 480-VOLT TRANSFORMER. THEY WERE ATTEMPTING TO ENERGIZE A LOCKOUT SWITCH BY TOUCHING AN INDEPENDENT 120-VOLT CONDUCTOR ONTO A TERMINAL INSIDE THE NETWORK PROTECTOR. THE THIRD EMPLOYEE WAS ON THE OTHER SIDE OF THE VAULT AT THE SOURCE OF THE 120-VOLT CONDUCTOR AT THE TIME OF THE ACCIDENT. A FAULT OCCURRED IN THE NETWORK PROTECTOR CAUSING A FLASH FIRE. TWO EMPLOYEES PROMPTLY ESCAPED FROM THE VAULT, BUT ONE OF THEM LATER DIED OF INJURIES HE SUSTAINED IN THE FLASH FIRE. THE OTHER REMAINED IN THE VAULT APPROXIMATELY 25 MINUTES, UNTIL THE EQUIPMENT COULD BE DISCONNECTED AT THE SUBSTATION AND THE ARCING STOPPED. THIS EMPLOYEE RECOVERED FROM HIS INJURIES. TWO ADDITIONAL EMPLOYEES SUFFERED SMOKE INHALATION FROM THEIR RESCUE EFFORTS. HOW THE FAULT OCCURRED AND HOW THE ARCING STARTED WAS NOT DETERMINED.