GAS-PHASE MASS-TRANSFER MODEL FOR PREDICTING VOLATILE ORGANIC-COMPOUND (VOC) EMISSION RATES FROM INDOOR POLLUTANT SOURCES

Analysis of the impact of sources on indoor pollutant concentrations a nd occupant exposure to indoor pollutants requires knowledge of the em ission rates from the sources. Emission rates are often determined by chamber testing and the data from the chamber test are fitted to an em pirical model. While the empirical models are useful, they do not prov ide information necessary to scale the chamber data to buildings nor d o they provide information necessary to understand the processes contr olling emissions. A mass transfer model for gas-phase-limited mass tra nsfer is developed and described in this paper. Examples of sources wi th gas-phase-limited emissions are moth cakes, floor wax, stain, and v arnish. The mass transfer model expresses the emission rate in terms o f a mass transfer coefficient and a driving force. The mass transfer c oefficient can be predicted from correlations of the Nusselt number an d the Reynolds number. The experiments and data analysis used to devel op the correlation are described in the paper. Experiments to verify t he assumptions used to describe the driving force are also described. Suggestions for using data from existing empirical emission models to determine parameters for the mass transfer model are provided. The mas s transfer model provides a significantly better fit to data from an i ndoor air quality test house than does the empirical first order decay model.