Toxicity and incapacitation due to hydrogen chloride

Hydrogen chloride is the principal product released during the combustion of poly(vinylchloride). It is classified as a sensory and pulmonary irritant. The toxicity of hydrogen chloride (HCl) has been the subject of numerous acute toxicological studies on rodents to determine the effect of HCl exposure on humans during fires. The lethality studies show that HCl destroys the upper respiratory tract and the eyes of rodents. A few of the rodent studies measured the HCl concentration required to produce incapacitation within a given short-exposure period. These concentrations were higher than the lethal concentrations due to the fact that most deaths occur post-exposure. The findings from rodent studies were basically confirmed by exposing non-human primates (baboons) to high HCl concentrations for 5 min and measuring escape potential. In the baboon study, no statistical significance could be found between the time-to-effect parameters, failure modes and the HCl concentrations. The relevance of the baboon behavioral model and physiological response to human escape-potential in a fire environment that contains HCl is questionable. In terms of the behavioral model, the baboons were able to carry out the escape routine with their eyes closed during the exposure. Inability to see was not considered incapacitating. Humans would have great difficulty escaping from a fire with their eyes closed. Furthermore, the baboons escaped by one simple action; jumping out. Most humans could not escape from a fire by one simple, instantaneous act. Based on the review of HCl toxicity and basic toxicological principles, elements required for the development of an appropriate animal incapacitation model for irritants are proposed. Exposure of animals to irritants, such as HCl, will only provide information on human escape impairment from fire when the animal models address the direct result of irritant effects on vision and respiratory function. Most of the preset studies measure the delayed, secondary systemic effects that produce asphyxia. Clearly, the measurement of vision or the lack of vision should be of primary importance in any irritant smoke incapacitation model.