Today was family day at Agusta Aerospace, located at 3050 Red Lion Road in Northeast Philadelphia. Employees and their families gathered for a day of fun in a helicopter hanger this morning.
Everything was relatively normal about the event until shortly before 11 a.m.. That's when authorities say an employee's child hit a button that said "don't hit button unless in an emergency". The button triggered the fire suppression system, filling the hanger with foam.
What you are seeing is high expansion foam. Basicly it is just soap bubbles formed by a fan type apparatus. This is used only in a confined space, such as a closed hangar. If used outside, the foam rises with the thermal updraft and doesn't do anything other than float away in the wind, as you see in some of the shots. The originally AFFF was VERY corrosive and would eat the impellers in the pumps of the old MB5 crash trucks. You could use it to clean brass. The new AFFF's are a detergent base and not nearly as corrosive.
To update: On last nights news, Fire officials said they now believe the cause to be "Sterno" chaffing dish fuel cans that the caterer was using. They believe the heat or smoke from the fuel set off a fire censor in the hanger.
The heat from the sterno cans are not enough to set off the detectors that would be high in the overhead. However, if the fire detection system had UV detectors, they trigger on flame. Still improbable unless someone somehow spilled one of the sterno cans and created a large enough flame to be detected.