Multi-target identification for emission parameters of building materials by unsteady concentration measurement in airtight micro-cell-type chamber

The purpose of this study is to develop a concurrent determination method that can estimate multiple emission parameters, that is, the emission rate, initial concentration and effective diffusion coefficient Dc in building materials, by a single unsteady concentration measurement. This study focused on the time history of VOC concentration in the gas phase that occurred when the target building material was covered with an airtight micro-cell. The VOC concentration in the micro-cell gradually increased and finally reached an equilibrium concentration. Under the condition of uniform distribution of initial concentration, the profile of VOC concentration in the micro-cell was determined by the order of the Dc value. A chart of the time history of VOC concentration as a function of Dc and thickness of building materials was prepared in advance by numerical analysis and then Dc was estimated by overlapping the measurement result with this chart. A chart of emission rate as a function of Dc and building material thickness was also prepared and the determination procedure of the emission rate taking into account the consistency between the 20 L small chamber method with in- and out-flow and the micro-cell method under an airtight condition was proposed. The estimation results of Dc and emission rate by this method were reasonably consistent with the results of the conventional method.