Biological Studies of Combustion Atmospheres

There is evidence supported by statistical information from fire deaths that many fire fatalities occur as a result of incapacitation of the victims by the toxic products given off during the early stages of fires, thereby preventing escape from the fire, rather than from direct exposure to heat or other factors. As an essential part of understanding these problems, a study has been made of the mechanisms of incapacitation resulting from exposures to atmospheres of ther mal decomposition products from polymeric materials. Under conditions ap proved by the Home Office Inspector, individual cynomolgus monkeys were ex posed to atmospheres increasing in separate experiments from very low smoke concentrations until early signs of physiological effects were detected. Measure ments were made of two kinds of physiological parameters: vital signs (respira tion, electrocardiography and respiratory blood gases) and parameters indicating effects on the nervous system (electroencephalography, auditory evoked poten tials, nerve conduction velocity). The atmospheres generated were designed to study the effects of hypoxia, hypercapnia, carbon monoxide, hydrogen cyanide and thermal decomposition products from wood, polyacrylonitrile, polyurethane foam, polypropylene, polystyrene and nylon produced under pyrolytic or ox idative conditions at a range of temperatures. The main findings were that the composition and hence the toxicity of the products from individual materials could vary considerably depending upon the different conditions of temperature and degree of oxygenation under which they were decomposed. However, despite the great complexity in chemical composition of the test atmospheres, the basic toxic effects on the animals were relatively simple, and for each in dividual atmosphere the toxicity was always dominated by one of these factors; carbon monoxide, hydrogen cyanide, or irritants. The role of each of these fac tors in causing incapacitation in real fires is discussed.