PHYSIOLOGIC MODELS FOR COMPARISON OF INHALATION DOSE BETWEEN LABORATORY AND FIELD-GENERATED ATMOSPHERES OF A DRY POWDER FIRE SUPPRESSANT

Abstract

SFE, a solid (dry powder) fire extinguishant, has been evaluated for fire suppression. A fire suppression atmosphere is achieved from pyrolysis of solid SFE, producing an atmosphere consisting of SFE pyrolysates (KCl aerosol particles, CO, and CO2). These components were found in differing proportion depending upon the amount of SFE pyrolyzed and type of testing being performed. Although the inhalation toxicity of this atmosphere has been addressed by laboratory studies, the atmospheres under use conditions were observed to vary from those used in the laboratory. Therefore, we devised a method to estimate the effects of these differences on dose. The deposited aerosol dose and formation of carboxyhemoglobin, which presumably reflect potential health risks, from inhalation of SFE in both situations were estimated by mathematical modeling in rats. The effects of CO2 stimulation of ventilation on aerosol particle deposition and carboxyhemoglobin formation were included. The physical and chemical properties of SFE atmospheres generated for large-scale fire suppression testing and for the acute inhalation toxicity evaluation were used as model inputs. Two nominal concentrations of SFE, 50 and 80 g/m3, were examined in both test systems. Predicted regional dose in the respiratory tract varied between the two cases, but carboxyhemoglobin formation was predicted to be greater for the fire suppression testing atmospheres.