Cyanide poisoning due to smoke inhalation from structural fires is potentially fatal and often occurs in the presence of carbon monoxide poisoning. Cyanide and carbon monoxide are common combustion products of residential and industrial structural fires. Cyanide impairs cellular respiration, and carbon monoxide decreases red blood cells' ability to transfer hemoglobin-bound oxygen from the bloodstream to body tissues. Fortunately, firefighters wear respirators during fire suppression activities, protecting them from direct smoke inhalation while fighting a structural fire. However, individuals trapped in a fire without respiratory protection are likely to suffer from smoke inhalation (a common cause of death among fire scene fatalities). Additionally, firefighters may experience more cyanide exposure than is realized due to the short half-life of cyanide in the human body, limiting the usefulness of blood samples collected for cyanide detection.

Reference:

Kurta A, et al. Cyanide poisoning by fire smoke inhalation, European Journal of Emergency Medicine: February 2013 - Volume 20 - Issue 1 - p 2-9.