Black soot visible on the surface of the airway indicates the decedent was alive at the time of the fire.

The presence of soot on the surface of the airway answers a critical question in death investigation: did the decedent die because they burned, or did they burn because they died? In other words, was the individual already dead at the time the fire was set, or did they expire due to thermal injuries and/or smoke inhalation?

Products of combustion do not move passively into the deep channels of the lung during a fire. If the pathologist is able to identify soot on the surface of the bronchi (the main entrances to the lungs) or any of the branching channels through which air moves throughout the respiratory system, she or he can say definitively if the victim was alive during the conflagration