AbstractA method is presented for evaluating the toxic hazard resulting from the thermal decomposition of materials used in buildings or other closed structures. It was developed in conjunction with the current revision of Israel Standards pertaining to the behavior in fire of building materials. The method is based on the measurement and evaluation of those gases recognized as hazardous in fire situations. A ‘toxicity ratio’ of the materials is defined in terms of the sum of concentration ratios of all toxic gases monitored to the corresponding lethal threshold limit concentration levels. The ‘toxicity index’, a material property, relates the toxicity ration to the material quantity and the plenum volume. The toxicity index is found by experiment for specimens heated to their smoldering and flaming temperatures in a closed system. Fire hazard levels due to toxic gases emitted from different materials can then be compared using the toxicity ratio computed for the specified situation. The proposed method is compatible with Israel Standards IS 921, where allowable levels for buildings and compartments are
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