Before the installations had started at a flour mill, at around 6 a.m., the technicians noted that a fire had started on a bag filter. The floor around the filter had started to burn, and they were alerted by the smell. Fire extinguishers were used in an attempt to put out the fire, and the fire brigade was called. The accident involved one of the three hot filters, which had an operating temperature between 160 and 170 °C. The personnel were evacuated. The emergency rescue services identified several hot spots although the fire had not spread to the storage silo. The filter was opened up and emptied, and the remaining flour was sprayed down with water. The bag filter and its operating valves were destroyed. The site’s activity resumed in the afternoon, except for the activity “parboiled flour” which was transferred to another site.

It is believed that the fire was caused by self-heating of the flour still present during the shutdown period. The remaining flour in the filter may have been caused by either a cleaning operation performed after the shutdown or by an obstruction created by a plug of flour. The presence of this residual flour had gone undetected. The shutdown of the air circulation fans at the same time as the steam system valve did not assist in rapidly cooling down the system when it was shut down. The high temperature of the oven’s walls thus would have heated up the flour that remained blocked in the installation.

The operator had proposed to implement a step at the end of the cycle to ensure that the filters are cleaned, to install a system able to detect the presence of steam in the filters and to modify the safety rounds. Plans have also been made to install an alarm in that would sound in the event of temperature measurement deviations. In addition, an alert and intervention procedure was drawn up.