Volatile organic compounds from the combustion of human and animal tissue.

The volatile by-products of the combustion of ordinary fuels such as wood, polystyrene, polyethylene, urethane foam, PVC and the like are well known to the forensic fire debris examiner. When a fire involves a human body, volatile species are produced that are not so well known, including various alkenes and aldehydes. These have sometimes been mistaken for the residues of unusual accelerants. In an attempt to document what volatiles are produced by the combustion of animal fat and human fat, the authors have used an open-tube pyrolysis probe as a microfurnace to burn small samples of unembalmed subcutaneous fat from human, avian and porcine sources, and collect volatiles by charcoal strip adsorption. The volatile products were analyzed by GC/MS. Predominant species included aldehydes in the C6-C10 range, homologous series of alkenes and alkanes, and other hydrocarbon products. These results were compared to those obtained by free-burning (open flame in air) of similar specimens and to the volatiles detected in debris from beneath a human cadaver in a test fire. Differences between the volatile profiles produced by human fat as compared to pork and chicken fat and adventitious sources of such volatiles are discussed.

Sustained combustion of an animal carcass and its implications for the consumption of human bodies in fires.

When a human body is found with significant portions of its torso and limbs destroyed yet with comparatively minor damage to head, hands and feet, the mechanism of such destruction defies ready explanation, since exposure to external fires, particularly those involving flammable liquids, usually results in the destruction of hands, feet, limbs, and head prior to significant combustion of the large mass of the torso. Previous tests by these authors have demonstrated the conditions necessary to promote combustion of a body: the presence of adequate body fat, presence of a porous, rigid char to act as a wick, and an external flame source sustained for several minutes to char the body and cause the subcutaneous fat to begin rendering. In the test reported here, a freshly-slaughtered pig carcass with a net weight of 215 lb. (95 kg) was wrapped in a cotton blanket and placed on a carpet-covered plywood panel. The fire was initiated using 1 L of gasoline poured on the shoulder area of the blanket-wrapped carcass. The gasoline burned off within 4 min, having ignited a large area of the blanket and adjoining carpet. Flames from those fuel packages resulted in the establishment of a steady-state fire sustained by the rendering of the body fat, with the necessary wick provided by the charred cotton blanket and carpet. The heat release rate of this fire was 60+/-10 kW, with flames less than 12 in. (0.35 m) high for its duration. The fire sustained itself by the rendering process for more than 6 1/2 h from ignition, at which time it was extinguished. An average mass loss rate of 1.5 g/s (5.3 kg/h) was observed during the self-sustained fire. Extensive destruction of the carcass (more than 60% by weight) included reduction of large bones to a fragile, ashen state. Other test data will demonstrate the similarity between subcutaneous fat from human and porcine sources. The implications for the reconstruction of accidental and homicidal fires involving such destruction will be discussed.

Combustion of animal fat and its implications for the consumption of human bodies in fires.

This paper describes experiments in which the combustion of animal tissue (pork) was measured under a variety of conditions that may be encountered in fire scenes. Combustion depends on substantial preheating of the tissue by an external heat source and the availability of a porous wick (such as charred cellulosic material). Combustion of moderate-size samples can proceed at a moderate rate of 1-3 g/s (3.6-10.8 kg/hr) if provided with an adequate wick and results in only a small fire of 30-50 kW. In the final test, combustion of 26 kg of fat and skin created a fire of 120-130 kW. Such a fire is more likely to cause fire spread to other combustibles nearby. The presence of other, less efficient fuels (like skin and muscle) and the absence of large fuel masses (such as in the very lean pig carcasses used here) results in significantly smaller fires of 40-50 kW. Such fires are more typical of burning human remains when there are minimal contributions from other fuels.

The dynamics of flash fires involving flammable hydrocarbon liquids.

Victims of fires are sometimes discovered to have less-than-lethal levels of carbon monoxide (CO) in the blood and no significant antemortem fire damage. Such occurrences are often linked to flash fires involving volatile hydrocarbon fuels. In this study, the dynamics of hydrocarbon fuel fires are examined, and the results of fullscale room tests ignited with small (< 2 L) quantities of flammable liquid are found to confirm the theoretical predictions. These tests showed that flame plumes with temperatures of 500-975 degrees C were produced above flammable liquids. Ignition of their vapors in a carpeted room produced a very short-lived flash of fire throughout the room, followed by intense flames in a layer above the floor approximately 1 m deep, which quickly degenerated to isolated pools of low flames. Combustion of hydrocarbon vapors in a room caused oxygen levels to drop below 8.5% in < 100 s, while causing carbon dioxide (CO2) levels to increase to 12-16% whether the door to the room was open or closed. Production of CO trailed maximum CO2 production by 15-30 s. A victim exposed to such a fire may collapse from extreme heat (aided by the water vapor created by the combustion of hydrocarbons), weakened by oxygen deprivation, before CO inhalation becomes a significant factor.