At 7.54 am in a nuclear research centre, the first aid team was called following the detection of smoke from a room used for the dismantling and decontamination of glove boxes, which are low level radioactive materials. The building was also used as a first aid centre and room for radioprotection; it was outside of the Basic Nuclear Installation (BNI). The building’s staff were evacuated for 2 hours, an internal crisis centre was activated at 8.35 am, the inspection authorities for classified facilities were alerted at 8.50 am and the gendarmerie (French military police) at 10.00 am. The risk of contamination was low and there was no external release thanks to the nuclear ventilation system’s operation. Firefighters arrived at the scene at 10.20 am and the fire went out by itself at 11 am. At 11.10 am, 2 officers specialised in radiological risks went on site and 2 others to the crisis centre at the Prefecture. The pre-filters were able to be changed that Friday afternoon and negative pressure was restored. On 8 December, in the evening, the installation had therefore been completed returned to a safe state. The installation of seals was requested by the prosecutor in the event of a malicious act. This smouldering fire was most likely caused by filter cutting work in view of their repackaging in 200 l packages carried out at the beginning of the afternoon on 7 December in this room. The waste should have been packed in drums after the cutting work and not left in polyester resin containers where the fire appeared to have smouldered. In addition, there was no hot work permit for the cutting work. The use of a disk-cutter for this work did not seem appropriate with a significant amount of paper (filters) present. Radiological monitoring of the unit was lost on 7/12 at around 7.10 pm, without doubt following clogging of the filter located above the containers of waste and was not identified immediately because it was only carried out in the unit during work periods. The PMS round had not detected anything either. The radiological consequences of this incident were zero (contamination below 4 Bq/cm2 in the unit and below 0.4 Bq/cm2 under the over-boots of the intervening officers). The crisis had been managed correctly by the research centre with evacuation of the staff and rapid intervention of the first aid team (7 min).