UNITED STATES
DEPARTMENT OF LABOR

Inspection Detail

Inspection: 125752659 - Mba Polymers, Inc.

Inspection Information - Office: Ca Concord (Psm N.)

Investigation Summary

Employees were working at a plastics recycling firm. The firm recycled plastic components, including toner cartridges, through a series of machines called the Alpha Line. The Alpha Line shredded, transported, and separated plastic, ferrous metal, nonferrous metal, and toner from plastic items making up the feedstock. At the time of the accident, employees were placing toner cartridges into a conveyor pit at the start of the Alpha Line. Employees were in all parts of the building. One employee was driving a forklift approximately 1.5 meters from the conveyor pit. An ignition source of unknown origin ignited toner from recycled toner cartridges, causing an explosion and ensuing fire. The forklift driver was killed in the fire. Four other employees, who were not listed on injury lines on the original form, suffered minor smoke inhalation. The components of the Alpha Line involved in the toner-dust explosion consisted of three conveyors, a shear shredder, a shaker table, an auger, and an eddy current separator. The components were manufactured by the following companies: conveyor #1 by Hustler, the shear shredder by SSI, conveyors #2 and #3 and the shaker table by B.E.S.T., and the auger by Screw Conveyor Company. The ventilation system was inadequate and inappropriately designed for the hazardous atmosphere generated by the toner. Although the precise ignition source for the toner was unknown, the low minimum energy necessary to ignite toner allows for a number of possible ignition scenarios for the explosion, including: static electricity from the Alpha Line's conveyor belts, static electricity on the ungrounded flexible ducts on the Alpha Line's ventilation system, an electrical discharge at the eddy current separator, static electricity from metal pieces in shredded toner cartridges, metal-on-metal sparking in the shredded toner cartridges, and electric equipment unapproved for the hazardous location near the Alpha Line.

Keywords:static electricity, ventilation, fire, explosion, combustible dust, equipment approval