On the 16th June 2000, an aluminum dust deflagration occurred in a small factory in the north-west of Italy. The explosion took place in an aluminum dust collecting and abatement unit that served a surface polishing plant. The collecting unit was made up of several ducts that conveyed dust into a manifold, which was connected to a cyclone and a bag filter. The cost of the deflagration cost was six injured workers, and relevant damage to the plant machinery, the process building and to other surroundings buildings. Although aluminum dust explosions are well known and have been well documented in the literature, this case study can be considered interesting because of its complex dynamics, which started with a first weak explosion that then evolved into a more severe chain of explosions. This article has drawn upon the official documents written during the investigation and the technical reports prepared by a number of expert witnesses. The data collected during the investigation have made it possible to determine the causes and dynamics of the accident and to calculate the strength of the explosion, on the basis of the distribution of the damage and the launching distance of the fragments. The magnitude of the damage seems to indicate that the amount of dust that took part in the explosion corresponds to the dust that settled on the bag filters. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.