Fire Safety Science Digital Archive

Studies of incapacitation and lethality in laboratory animals and human fire victims, resulting from exposure to thermal decomposition products from many materials, indicate two main mechanisms of toxicity, narcosis (asphyxia) and irritancy. Narcotic effects are caused by the common asphyiant gases, GO, HCN, low 02, and C02 and can be predicted to a reasonable degree with existing knowledge. Irritant effects are caused by a variety of combustion products some of which are unknown, but can be quantified from small scale rodent combustion toxicity tests in terms of the mass loss concentration of combustion products (RD and LC in mg.min/liter). A mathematical model is presented for estimating toxic and physical hazard in fire in terms of time to incapacitation or death. The model takes the concentration/time profiles of the above products, smoke optical density, temperature and radiant heat flux (derived from other mathematical models or large scale fire tests) and calculates time to incapacitation using a Fractional Effective Dose method based upon the known toxic effects of the combustion products, and of the physical hazards, in man, primates and rodents.