One particular machine was identified. It coated strips of rubber by dipping in "Acumist", a finely powdered grade of combustible polyethylene. This machine had operated for 24 hours a day, five or six days a week, since 1987. The spaces around the machine, including a suspended ceiling above the machine, were regularly cleaned by the factory's maintenance personnel. But they were unaware that ventilation systems within the room pulled the dust up into the ceiling, where a layer thick had accumulated. Several weeks prior to the accident, maintenance personnel did notice a thick coating of dust on surfaces above the suspended ceiling, but failed to realize the imminent danger it posed.