During a regular facility inspection inside a silo, the Head of Operations saw smoke rising from 2 intercellular storage spaces (so-called “ace of spades”); he immediately shut down the installations. Fire-fighters controlled this combustion event, resulting from an accumulation of cereal dust, by means of injecting water and draining a hopper. No property damage was reported. During the emergency response, a detailed inspection showed that dusts had accumulated on the upper part of the storage cells (ceiling and walls) over a 1-m height: the walls of these zones had not been cleaned by the drainage effect. Given their concrete cover, these cells were not easily accessible for cleaning purposes. The accumulation thickness had reached several cm in a hopper that had been systematically used for silo cell drainage operations. An explosive dust cloud could have easily formed. The ongoing safety report concerning this silo was complemented by a specific section on the handling tower hopper.