Most times the computer or black box starts to record data after an event such as an impact. Im mot sure if it will show anything about a fire but may show some stuff depending on vehicle such as RPM, braking applied, seat belt fixed etc but can depend again on type of vehicle and system, There area company's that are equipped to do this sort of down load. I would look them up and give them a call and ask exactly what type of data may or may not be recorded in a fire event.