Fundamental Mass Transfer Model for Indoor Air Emissions from Surface Coatings

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Abstract
Emissions from freshly applied paints and other coatings can cause elevated indoor concentrations of vapor-phase organics. Methods are needed to determine the emission rates over time for these products. Some success has been achieved using simple first-order decay models to evaluate data from small dynamic test chambers. While such empirical approaches may be useful for assessing the emission potmial of indoor sources, a more fundamental approach is needed to fully elucidate the relevant mass transfer processes. As a first step, a simple model based on boundary layer theory has been developed. In this model, the mass transfer rate is assumed to be controlled by the boundary layer mass transfer coefficient, the saturation vapor pressure of the material being emitted, and the mass of volatile material remaining in the source at any point in time. Static and dynamic chamber tests and test house experiments were conducted to obtain model validation data, Preliminary validaion results indicated that the model can be applied to different products with similar solvents. The model provides a better fit to chamber-derived emissions data than the empirical first-order decay model, especially over the decaying portion of the concentration vs. time curve