In an automobile equipment plant, fire broke out around 1 pm in the vestibule of a heat treatment oven prior to brazing, upon restarting the furnace after it had been moved. In-house fire-fighters controlled the outbreak using extinguishers and cooled the outer part of the oven. Though notified, first responders were not required to intervene. The accident was due to obstruction of an air extraction duct by deteriorated insulation. The lack of a temperature and air flow measurement sensor allowed the malfunction to go unnoticed. The operator responded by repositioning the installation’s insulation by inserting it between two metal sheets, undertaking air flow adjustments in conjunction with the supplier, and having the technician implement a temperature monitoring system along with an air intake visual inspection hole. The operator also announced plans to verify the safety of oven operations by a third party, identify a technical solution to monitor both flow rate and temperature, and extend the technical and organisational improvements introduced on the damaged installation to the site’s six other furnaces.