An internal dose model for interspecies extrapolation of immediate incapacitation risk from inhalation of fire gases.

A quantitative mathematical model assesses incapacitation risk in humans from toxic gas inhalation. A body-mass-normalized internal dose for each gas is calculated from an inhalation equation in which ventilation is a function of species, activity, and the gases inhaled. Uptake in the dead space considers U.S. Environmental Protection Agency (EPA) gas categories. The probability of incapacitation is a function of normalized internal dose and follows a cumulative distribution curve whose parameters are found from small-animal incapacitation data. No internal interaction of gases is modeled, and probabilities are combined independently. The model compares favorably with combined gas and large-animal incapacitation data.