Surest proof of antemoem burn is
In case of burns, if death has occurred from suffocation,aspirated blackish coal paicles are seen in the nose,mouth,larynx,trachea,bronchi,oesophagus and stomach, and blood is cherry red. Presence of carbon paicles especially in the terminal bronchioles and an elevated CO saturation together are absolute proof that the victim was alive when the fire occurred. In the absence of CO in blood and soot in the airways,death may possibly result due to poisoning with carbon dioxide or deficiency of oxygen. Sometimes inhalation of smoke produces vomiting which may be inhaled and found in the smaller bronchi. Ref: K.S.Narayan Reddy's Synopsis of Forensic Medicine and Toxicology, 29th edition, Chapter 11, page-163.
Heat rupture
Presence of soots beyond the tracheal bifurcation
Blackening of bones
Clean laryngeal airway
Death and postmortem changes