First Interstate Bank, Los Angeles — Five Floors Gutted in the Worst U.S. High-Rise Fire

The First Interstate Bank tower, a 62-storey, 860-foot steel-framed high-rise in downtown Los Angeles, was gutted across five floors — the 12th through the 16th — by a fire that began on the evening of 4 May 1988, killing one person and injuring roughly forty. The proximate cause was not the ignition, an ordinary electrical fault in an open office floor of furniture and computer workstations, but what the building did with it: a fully developed, post-flashover fire climbed the tower floor to floor through the exterior wall, because its single most important active defense — a sprinkler system — was 90 percent installed and completely inoperative on the night it was needed.

The fire reached temperatures that buckled and sagged the protected steel floor framing, blew out windows, and propagated upward by autoexposure — flame venting from a broken window and re-entering the floor above — aided by the failure of the firestop in the narrow gap between each floor slab edge and the glass curtain wall. No floor collapsed; the building survived as a structure and was repaired, but five floors burned out completely. It is the case forensic engineers cite to show that a modern steel high-rise can be brought to the edge of structural failure not by a flaw in its frame but by the timing of a retrofit.

Completed in 1973 as the tallest building in Los Angeles, the tower had been built and operated legally without sprinklers: the city’s 1974 high-rise ordinance applied only to new construction and grandfathered existing buildings. By 1988 the owner was voluntarily installing sprinklers throughout, but on the night of the fire the system was unfinished and dry — contractors had shut the fire pumps down at 22:22 to make connections, and the smoke detectors, repeatedly triggering during the work, had been treated by security as nuisance alarms.

The National Bureau of Standards (now NIST) and the Los Angeles Fire Department both produced engineering post-mortems. Neither found a defective building. They found a defended building with its defense switched off, and a fire-spread path — the curtain-wall perimeter joint — that automatic suppression existed precisely to keep from ever opening. First Interstate became the byword for two lessons at once: that existing high-rises must be sprinklered, not merely new ones, and that a partly installed life-safety system is, for the duration of the work, no system at all.

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