Calculating FED and LC50 for testing toxicity of materials in bench-scale tests with a cone calorimeter

Thermal properties and smoke toxicity upon burning combustibles, especially polymers, are two key aspects to be considered in fire hazard assessment. The cone calorimeter is demonstrated to be a useful bench-scale apparatus to evaluate the thermal properties. Even some key parameters on smoke, such as the smoke extinction area, the carbon dioxide and carbon monoxide concentrations can be measured. As most cone tests are conducted under well-ventilated conditions, there are arguments on whether the cone calorimeter is suitable for assessing the smoke toxicity. In this paper, the calculation procedure for the 'lethal concentration of the fire effluent emitted to produce death in 50% of test animals for a specified exposure time' LC50and the fractional effective dose FED based on the cone data will be clarified. The objective is to inspect how the concentrations of toxic gases upon burning polymers can be derived from such bench-scale tests. Cone data on polycarbonate sheets are taken as examples to illustrate the procedure. The values of LC50deduced from measuring only the carbon monoxide will be discussed. From the study, there might be misinterpretation in using the gas concentration measured in the duct of the cone calorimeter. An appropriate control volume should be taken to ensure that all toxic products are collected.