On most nights, the university’s chemistry lab housed one or two ambitious students working diligently into the wee hours of the morning. But tonight, unlike most nights, it was empty. Without the students, the lab held an eerie quiet. A household refrigerator, the room’s only occupant, hummed softly against the south wall.

Chemicals stored inside the consumer-grade refrigerator slowly exhaled a volatile vapor. Every few minutes the refrigerator’s defrost timer created a small arc of electricity inside its housing. This ritual repeated itself many times, yet the vapor and the arc ignored each other. But at 3:29 A.M. they met at last. The explosion ripped the refrigerator door from its latch and hinges. The door hurtled across the room, tore through a window and began its descent to the parking lot three stories below.

Back in the lab, a sprinkler system celebrated the happy union of arc and vapor by inundating the room and its contents with water…