Abstract: The basic situation and field investigation process of a fire case were introduced. The typical fire trace characteristics under the condition of convection ventilation were analyzed combined with case study. The preliminary analysis was carried outaccording to the site investigation. The mobile phone video of the first alarm person and on- site personnel was accessed. Combing with the results of inquiry and electrical inspection and residue detection, inviting fire accident investigation experts to assist in the investigation, the seat of fire was determined. The typical interference trace characteristics caused by convection ventilation are summarized combined with the case and fire investigation experience, and methods and countermeasures of fire location identification were discussed from 5 aspects.

Key words: fire investigation;traces of the scene;convectional ventilation, seat of fire