The Fire

The starting of a fire depends on an ignition source, a sufficient quantity of flammable material near the source, and an adequate oxygen (O2) supply (4,30). Combustion raises the temperature and produces a visible glow or flame (31). Temperatures higher than 150°C (300°F) are reached in building fires within 5 to 10 min (32). In close confines (e.g., an aircraft cabin), a rapidly fatal temperature of about 250°C (480°F) occurs in 5 to 6 min (33). If a door is opened or the integrity of an enclosed structure is breached by heat, then the sudden introduction of O2 leads to flashover, i.e., a sudden burst of flame as the spontaneous ignition temperature of gases and other combustion products is reached (33). Flashover is likely above 650°C (1200°F [33]). Temperatures higher than 1000°C (1832°F) happen within minutes when an airplane occupant compartment is compromised (33). Temperatures in car fires can be up to 1100°C (1980°F),

Fig. 1. Cases of suicides by fire (self-immolation). Victims alive during fire (smoke inhalation and elevated carboxyhemoglobin). (A) Found under hood of burned vehicle in remote area. (B) Manacled (arrow) to steering wheel. (Reprinted, with permission, from ref. 18 and the Journal of Forensic Sciences, copyright ASTM International, West Conshohocken, PA.)

Fig. 1. Cases of suicides by fire (self-immolation). Victims alive during fire (smoke inhalation and elevated carboxyhemoglobin). (A) Found under hood of burned vehicle in remote area. (B) Manacled (arrow) to steering wheel. (Reprinted, with permission, from ref. 18 and the Journal of Forensic Sciences, copyright ASTM International, West Conshohocken, PA.)

particularly if fuel is present (34-36). Radiating heat in a high-temperature fire (up to 980°C or 1800°F) in an enclosed space can spontaneously ignite furniture (4).

Initially, carbon-containing materials are oxidized to carbon dioxide, and carbon monoxide (CO) production is low (see Chapter 3, Subheading 3.9. and ref. 31). Pyrolysis is the decomposition of a substance under the influence of heat and does not require a normal atmospheric level of O2 ("incomplete combustion" [31]). Because the O2 supply is consumed and not readily replenished in a poorly ventilated space, pyrolysis leads to the production of smoke (airborne particles) admixed with toxic gases, such as CO

Fig. 2. Fatal house fire. Self-inflicted nonfatal abdominal wound (arrow). Smoke inhalation and elevated carboxyhemoglobin (39%). Extensive burns.

Fig. 3. Dead prior to fire. Apparent accidental car fire concealing a homicide. No evidence of smoke and carbon monoxide inhalation. (A) Radiograph of skull. Multiple bullet fragments. (B) Top of skull burnt and missing. Probe inserted through gunshot hole in base of skull showing track to recovery site of largest bullet fragment (courtesy of the Office of Chief Medical Examiner, Chapel Hill, NC).

Fig. 3. Dead prior to fire. Apparent accidental car fire concealing a homicide. No evidence of smoke and carbon monoxide inhalation. (A) Radiograph of skull. Multiple bullet fragments. (B) Top of skull burnt and missing. Probe inserted through gunshot hole in base of skull showing track to recovery site of largest bullet fragment (courtesy of the Office of Chief Medical Examiner, Chapel Hill, NC).

(30,31,33,37). If flashover occurs, pyrolysis yields chemically unstable complex compounds, and CO production increases (31,33).

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