Death may be due to the effects of breathing the products of fire/ burning, principally carbon monoxide, but also cyanide and many other toxic by-products of combustion. Alternatively, death may be due to the effects of heat (i.e. heat shock), or the inhalation of hot air/ gases, possibly related to the initiation of a vagally-mediated ‘reflex’ cardiac arrest following the stimulation of nerve endings in the pharynx/larynx.
The effects of heat and smoke/ fumes are usually more rapid (in a house fire) than the effects of direct injury from flames; an assessment of the body surface area affected by burns (using the clinical ‘rule of nines’ method) should, however, still be performed. It is often difficult to determine what represents ante mortem vs. post mortem burning; reddening of the edges of the burns may point to an ante mortem aetiology, but this is not conclusive.
The significance of trauma may be equally difficult to determine – perimortem injuries can not be effectively ‘aged’, and it may therefore be impossible to state with any confidence whether injuries resulted from ante mortem trauma (and therefore may be relevant to the cause of death) or were caused post mortem.
A review of fire-related deaths in Cardiff found that 10% of fire-related deaths occurred following hospitalisation. Such deaths may be due to: